Andrés Núñez Meneses

Pierre Lacan
email: placan@geociencias.unam.mx

Ramón Zúñiga

Laurence Audin

María Ortuño

José Rosas Elguera

Rodrigo Leon-Loya

Víctor Márquez

First paleoseismological results in the epicentral area of the sixteenth century Ameca earthquake, Jalisco -México

Keywords: Paleoseismicity, historical seismicity, sixteenth century Ameca earthquake, Trans-Mexican Volcanic Belt, Central Mexico, Seismic hazard

The Trans-Mexican Volcanic Belt (TMVB) is a calc-alkaline volcanic arc cut by different active crustal fault systems that have originated several destructive historical earthquakes. Located in the central part of Mexico this region offers exceptional climatic, and fertility of soil conditions, which is the reason why more than 50% of the Mexican population now live here, increasing the seismic risk. Determining the seismic potential of these fault systems is important in the western section of the TMVB, in the vicinity of the city of Guadalajara, where more than 5 million inhabitants are concentrated in a densely populated urban area.

We focus here on the epicentral area of the M W 7.2 sixteenth century Ameca earthquake, one of the first earthquakes described to take place in the American continent and which also may be the largest crustal earthquake to have occurred in the TMVB in the historical record. According to some historical sources, this earthquake would be associated with the Ameca-Ahuisculco Fault but no neotectonic study has been carried out so far to characterize this fault. Here, we describe the geomorphology of the fault escarpment and the characteristics of different fault segments. This first step allowed to select a suitable site for a paleoseismological study to track the historic event. The results of the interpretation of J o u r n a l P r e -p r o o f two trenches are consistent, showing evidence of net activity of the fault in the tectonosedimentary record with two and possibly three seismic events. The older one of these is not well recorded and interpreted as a possible event that could have occurred after 27,91 ± 0,4 cal ka BP and before 5,67 ± 0,064 cal ka BP. The second one and best recorded event occurred around 5,67 ± 0,064 cal ka BP whilst the last one occurred after 0,985 ± 0,065 cal ka BP and is likely to be the geological record of the Ameca sixteenth century earthquake.

Considering the potential rupture lengths and the coseismic displacement measured in the trenches, this fault system seems capable of generating earthquakes of magnitude 6.9 to 7.3 and represents a major source of earthquake hazard to the city of Guadalajara.

1-Introduction

Hundreds of potentially active faults intersect the Trans Mexican Volcanic Belt (TMVB), a volcanic arc that crosses central Mexico from the Pacific Ocean to the Gulf of Mexico [START_REF] Suter | Quaternary intra-arc extension in the Central Trans-Mexican volcanic belt[END_REF][START_REF] Ferrari | Digital Geologic Cartography and Geochronologic Database of the Trans-Mexican Volcanic Belt and Adjoining Areas[END_REF]. Due to the fertility of its soils and its climate, this intraplate volcanic arc has been particularly attractive to human settlement for thousands of years. Currently, more than half of the Mexican population lives in this geological province where the largest cities of the country are concentrated. The scarcity of studies on the seismogenic potential of these faults puts into question the validity of seismic hazard estimates in the national building rules and regulations (e.g., Instituto Nacional de Electricidad y Energías Limpias, 2017) and other regional bylaws (e.g., Reglamentos construcción México, 2020).

The period covered by the catalog of instrumental seismicity is clearly insufficient to characterize the activity of the slow-moving crustal faults of the TMVB [START_REF] Zúñiga | Temporal and spatial evolution of instrumented seismicity in the Trans-Mexican Volcanic Belt[END_REF]. However, the historical earthquake catalog (Suárez et al., 2020b), which covers the last 500 years, seems to indicate that many of the fault systems in the TMVB may be active and capable of producing destructive earthquakes with significant damage and loss (Fig. 1; [START_REF] J O U R N A L P R E -P R O O F Suárez | Active Crustal Deformation in the Trans-Mexican Volcanic Belt as Evidenced by Historical Earthquakes During the Last 450 Years[END_REF]. Unfortunately, the low slip rates of these faults and long return times J o u r n a l P r e -p r o o f of the major earthquakes that cover hundreds to thousands of years, greatly reduce the time window and make these catalogues of insufficient relevance to evaluate the related hazard.

In such a context, paleoseismological studies have emerged as effective tools for improving the knowledge on the seismogenic potential of faults over a period of several tens of thousands of years. Until now, most of the studies carried out in Mexico have been conducted in the central part of the TMVB, showing that most of the faults of the Morelia-Acambay fault system are active, with recurrence periods for M>6 earthquakes of several thousand years, calculated for individual faults (e.g. [START_REF] Langridge | Paleoseismology of the 1912 Acambay earthquake and the Acambay-Tixmadejé fault, Trans-Mexican Volcanic Belt[END_REF]2013;[START_REF] Suter | Structure and Holocene rupture of the Morelia fault, trans-Mexican volcanic belt, and their significance for seismic-hazard assessment[END_REF][START_REF] Lacan | Sedimentary evidence of historical and prehistorical earthquakes along the Venta de Bravo Fault System, Acambay Graben (Central Mexico)[END_REF][START_REF] Soria-Caballero | Evidence for quaternary seismic activity of the La Alberca-Teremendo fault, Morelia region, Trans-Mexican Volcanic Belt[END_REF][START_REF] Ortuño | Holocene paleo-earthquakes recorded at the transfer zone of two major faults: The Pastores and Venta de Bravo faults (Trans-Mexican Volcanic Belt)[END_REF][START_REF] Suter | The 1563 Mi 8 Puerto de la Navidad subduction-zone and 1567 Mw 7.2 Ameca Crustal earthquakes (Western Mexico): New insights from sixteenth-century sources[END_REF].

Considering that hundreds of potentially active faults have been identified in the TMVB, it is thus likely that several major earthquakes may occur each century (Suárez et al., 2020a).

One of the first colonial records of crustal earthquakes in the American continent is related to the sixteenth century Ameca earthquake (Fig. 1). On the basis of a compilation of historical documents, [START_REF] Suárez | Active crustal deformation in the Jalisco block, Mexico: evidence for a great historical earthquake in the 16th century[END_REF] were able to estimate the intensity values, calculate a magnitude between 7 and 7.8 and establish the location of the epicenter on the faults bordering the Jalisco block, to the southwest of Guadalajara. More recently, using the same documents as [START_REF] Suárez | Active crustal deformation in the Jalisco block, Mexico: evidence for a great historical earthquake in the 16th century[END_REF] and a historical document called "Relación de Ameca", [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF][START_REF] Suter | The 1563 Mi 8 Puerto de la Navidad subduction-zone and 1567 Mw 7.2 Ameca Crustal earthquakes (Western Mexico): New insights from sixteenth-century sources[END_REF] suggested the earthquake occurred on the Ameca-San Marcos normal fault system, whose complete rupture length can be empirically related to a magnitude of 7.2 ± 0.3.

Considering the work cited above and the fact that the geomorphological expressions of the fault escarpments indicate a possible persistent tectonic activity [START_REF] Castillo | Response of a landscape to tectonics using channel steepness indices (k sn ) and OSL: A case of study from the Jalisco Block, Western Mexico[END_REF], this fault system could represent a major hazard for the region. As a contribution to the geological characterization of this seismogenic fault, we present here the first paleoseismological study in the western part of the TMVB with the focus on the prehistoric seismic activity of the Ameca-Ahuisculco fault (AAF), the northernmost fault of the Ameca-San Marcos fault system. To do so, detailed geomorphological mapping of faults in the region was conducted with the aim to identify a site having suitable conditions for the preservation of the sedimentary record of earthquakes. Two trenches were dug and the units displaced by faults were sampled for radiocarbon dating, to infer the paleochronology of surface ruptures recorded. The scope of this study covers the assessment of the occurrence J o u r n a l P r e -p r o o f of potentially large earthquakes on this well-defined fault segment of the AAF during historical and pre-historical times to quantify their number, magnitudes and recurrence times. This works represents the first step of a long-term effort to assess the seismic hazard of low slip rate active faults in the vicinity of the megacity of Guadalajara.

2-Seismotectonic setting

The Ameca-Ahuisculco fault in the Trans Mexican Volcanic Belt

The tectonically active crustal structures of the TMVB are distributed in an arrangement of segmented normal fault systems spread over 900 km between, the Gulf of Mexico and the Pacific coast (Fig. 1; Ferrari et al., 2012 and references therein). These fault systems are mainly east-west oriented in the central TMVB, while the Tepic-Zacoalco and Colima fault systems, on the western TMVB, show respective NW-SE and N-S orientations, bordering the Jalisco Block (Fig. 1). South of Guadalajara, the intersection between the Chapala, Tepic-Zacoalco and Colima fault systems forms the triple-junction of Guadalajara (Fig. 1).

The studied area is located in the Tepic-Zacoalco fault system (TZFS) near the triplejunction mentioned above. The TZFS extends over a distance of 250 km, forming the northeast boundary of the Jalisco Block (Fig. 1;Allan, 1986). The TZFS is made up of different fault subsystem expressed as grabens and half-graben, mainly formed between the late Miocene and the Quaternary [START_REF] Ferrari | Late Miocene to Quaternary extension at the northern boundary of the Jalisco block, western Mexico: The Tepic-Zacoalco rift revised[END_REF]. The extension across the TZFS is constrained by GPS measurement to be ≤8 mm/year [START_REF] Selvans | Pure and Applied Geophysics Constraints on Jalisco Block Motion and Tectonics of the Guadalajara Triple Junction from 1998 -2001 Campaign GPS Data[END_REF] that could result in an earthquake recurrence time of 1,250 years for this fault system [START_REF] J O U R N A L P R E -P R O O F Suárez | Active Crustal Deformation in the Trans-Mexican Volcanic Belt as Evidenced by Historical Earthquakes During the Last 450 Years[END_REF]. At the southeastern end of the TZFS, the Ameca-Ahuisculco fault, consists of a ~55 km network of south dipping normal fault segments delimiting the plutonic to volcanic basement north of the fluvio-lacustrine filling of the Ameca valley to the south [START_REF] Rosas-Elguera | Stratigraphy and tectonics of the Guadalajara region and triple-junction area, western Mexico[END_REF][START_REF] Ferrari | Late Miocene to Quaternary extension at the northern boundary of the Jalisco block, western Mexico: The Tepic-Zacoalco rift revised[END_REF]; Fig. 2).

The sixteenth century Ameca earthquake

J o u r n a l P r e -p r o o f

The instrumental seismic catalogue does not show clear evidence of micro-or macroseismicity related to the AAF [START_REF] Zúñiga | Temporal and spatial evolution of instrumented seismicity in the Trans-Mexican Volcanic Belt[END_REF]. On the other hand, studies of historical seismicity by [START_REF] Suárez | Active crustal deformation in the Jalisco block, Mexico: evidence for a great historical earthquake in the 16th century[END_REF]Suárez et al., ( , 2020a) ) highlight the occurrence of a significant earthquake (M 7-7.8) which affected the area in 1568 and caused major destruction in the villages and towns located near to the faults bordering the Jalisco block, along the Tepic-Zacoalco and Colima fault systems. More recently, mainly based on descriptions of the 1579's colonial document called "Relación de Ameca" [START_REF] Acuña | Geology of the Northern Colima and Zacoalco Grabens, southwest Mexico: Late Cenozoic rifting in the Mexican Volcanic Belt[END_REF], [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF][START_REF] Suter | The 1563 Mi 8 Puerto de la Navidad subduction-zone and 1567 Mw 7.2 Ameca Crustal earthquakes (Western Mexico): New insights from sixteenth-century sources[END_REF] identified the AAF as well as the Villa Corona and the San Marcos Faults as the rupturing faults, responsible for the earthquake (Fig. 1B). Along these fault systems, [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF] calculated a 54-59 km long surface rupture and a scarp of 1,67 to 3,34 m associated with the event. [START_REF] J O U R N A L P R E -P R O O F Suárez | Active Crustal Deformation in the Trans-Mexican Volcanic Belt as Evidenced by Historical Earthquakes During the Last 450 Years[END_REF] estimated a magnitude of 7.2 ± 0.2 for this earthquake based on the inversion of intensity data, making it the strongest known cortical earthquake in central México. [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF] also reevaluate the date of the earthquake to 1567; however, the inconsistencies between historical documents, possibly linked to the passage from the Julian to the Gregorian calendar between the dates of occurrence of the earthquake and the drafting of the documents describing it, do not allow to close the debate about the exact date of the earthquake that will therefore be referred to as the sixteenth century Ameca earthquake in this study [START_REF] Suárez | Active crustal deformation in the Jalisco block, Mexico: evidence for a great historical earthquake in the 16th century[END_REF][START_REF] Suter | The 1563 Mi 8 Puerto de la Navidad subduction-zone and 1567 Mw 7.2 Ameca Crustal earthquakes (Western Mexico): New insights from sixteenth-century sources[END_REF]2020a;[START_REF] Suter | Comment on "Active Crustal Deformation in the Trans-Mexican Volcanic Belt as Evidenced by Historical Earthquakes During the Last 450 Years[END_REF].

3-Methods

A geomorphological study of the AAF has been carried out in order to precise the geometry, length and segmentation of the fault and identify the optimal site for the excavation of paleoseismic trenches. The recompilation of the available bibliographic documents as well as geological maps on a scale of 1:50,000 allowed us to trace a first approximation of the fault system and to identify uncertainties in its geometry. After that, the study of digital elevation models of different resolutions, available on the websites of the National Institute of Statistics and Geography (INEGI) or Japanese Space Agency (ALOS satellite, 12 m resolution) as well as the study of the aerial photographs available, allowed us to map the geometry and segments of the AAF. On this basis, different potential J o u r n a l P r e -p r o o f trench sites were identified. The optimal sites for paleoseismic trenching were decided conducting a field survey.

During February 2019, two trenches (Buenavista 1 and 2) were excavated with a backhoe excavator, perpendicularly to the inferred fault trace. Excavations were between 12 and 16 meters long and 2 meters deep, exposing the moderately preserved fault scarp. Following classical methods for paleoseismic survey across normal faults [START_REF] Mccalpin | Paleoseismology[END_REF] the trench walls were gridded (1m x 0,5 m) and logged. The photomosaics of the walls are available in the supplemental material. Three samples of paleosols (Bulk) were taken from the west wall of Buenavista 1 trench and processed by the LMC14-CEA Saclay laboratory, GIF sur Yvette, France. Radiocarbon ages were calibrated using the OxCal 4.3 program (Bronk Ramsey, 2009) and expressed in calibrated years before present (cal. BP).

4-Geomorphology of the Ameca-Ahuisculco fault

The AAF extends WNW-ESE to NW-SE, nearly 55 km from the Ameca range to the southern end of the Ahuisculco range (Fig. 2). It constitutes the NNE boundary of the Ameca half-graben [START_REF] Rosas-Elguera | Stratigraphy and tectonics of the Guadalajara region and triple-junction area, western Mexico[END_REF]. According to our analysis, the AAF can be divided into three main fault segments based on its morphology; the western, central and southeastern AAF.

The western AAF (1 in Fig. 2A) comprises four overlapping branches with different orientations that separate the Ameca range, mainly composed of competent plutonic and andesitic to basaltic volcanic rocks, from the Ameca alluvial plain. Two WNW-ESE oriented main branches cut the topography of the southern flank of the Sierra Ameca by a 50 to 90 m high escarpment (1a and 1d in Fig. 2A). The branch 1a is 4 km long next to the Ameca range and possibly extends up to 10 km westward, considering that it may continue into the alluvial plain (Yánez Mondragón y Rosales Gómez, 2005). The 1d strand extends 20 km and its escarpment height varies between 40 and 90 m, showing triangular facets, while the total height of the mountain front reaches 1000 m above the plain. These two main branches of similar orientation and height are connected by two smaller NE-SW and E-W oriented strands (1b and 1c in Fig. 2A). Branch 1b is 5 km long and displaces the topography by a 10 to 20 m escarpments, 1c is located in the down-thrown block controlled J o u r n a l P r e -p r o o f by 1d. It is 7 km in length and displaces the alluvial fans that come down from the Ameca range by 2 to 5 m. This last strand appears to be more recent than the others and, its orientation suggests a new stage in the growth of the fault system.

The central AAF segment (2 in Fig. 2A) is made up of different branches having the same orientation and the same SSW dip direction as the western segment. There is no clear separation between these two segments but more of a morphological break, the first segment corresponding to the southern border of the Ameca range. For the second segment, the main strand is 17 km in length with a scarp height that varies from 2-6 m in the alluvial valley floor of the Ameca River to 10-35 m in the pyroclastic flows of the northern Ahuisculco range. North of this main fault branch, there are three small strands of 3 to 10 km length, with scarp heights that vary between 3 and 15 m, affecting the pyroclastic flows of Ahuisculco range.

The southeastern AAF segment is 14 km long (3 in Fig. 2A) and conforms the southwestern edge of the Ahuisculco range. Its NW-SE orientation forms an angle of ~ 40° with the fault segments described above, and could correspond to a transitional zone between the Tepic-Zacoalco and the Colima fault system. There is no clear geomorphic segmentation between the central and southeastern segments which present a topographic escarpment varying between 50 and 100 m. Their distinction is mainly related to their difference in orientation.

Trench site location

The western and southeastern AAF segments (1 and 3 in Fig. 2A) present relatively high scarps and are, therefore, unlikely to have preserved recent sedimentary units affected by the fault. In contrast, the central segment (2 in Fig. 2A) affects a relatively flat area between the Ameca and the Ahuisculco mountain ranges where the sedimentary record of earthquakes is more likely to have been preserved. An ideal site would have been within the intersection of the alluvial plain of the Ameca river and the central fault scarp.

Unfortunately, an irrigation channel was built at the foot of the escarpment, destroying potential markers of past tectonic activity of the fault (Fig. 3A). In the central part of the fault segment, near to Buenavista village (< 2km, Fig. 3A), the fault scarp can be easily observed; it is relatively low (5 to 10 m) and is not affected by human activity, other than J o u r n a l P r e -p r o o f agriculture (Fig. 3B andC). In the field, the fault trace can be followed and traced using the changes in vegetation related to the composition and changes in the permeability of the basement rocks (Figs. 3D, E andF). Additionally, logistical factors such as easy access and authorization to dig trenches were determining for the selection of the study site. With the help of a backhoe, Buenavista 1 and 2 trenches, 16 and 12 meters long respectively, were excavated 20 m from each other, perpendicular to the fault trace.

Paleoseismic Trenching

Trench stratigraphy

At Buenavista site, the fault separates the volcanic rocks of the Ahuisculco range from the sedimentary rocks of the Ameca alluvial plain. Buenavista 1 and 2 trenches expose a volcano-sedimentary sequence consisting of 7 units named A to G from younger to older (Fig. 4). These units are easily correlated between the two trenches and described in detail in Table 1. Three samples were taken in the western wall of Buenavista 1 trench of units F, E and B for radiocarbon dating.

At the bottom of the trenches, Unit G (UG) is interpreted as a pyroclastic flow composed of up to 60 cm diameter sub-angular blocks of andesitic to dacitic composition. This unit is only visible in the up-thrown block where it is barely covered by the current soil (Unit A) at the two trenches (Fig. 4).

In the downthrown block the same 5 units are observed in the two trenches. At the bottom, unit F (UF) is a colluvial unit composed of a chaotic accumulation of blocks of different compositions embedded in a heterogeneous matrix composed of reworked and mixed paleosols and very fine ashy deposits. Despite the fact that only the upper part of this unit is observed in the 2 trenches, its geometry and its chaotic organization suggest that it is likely to be a colluvial wedge related to a surface rupture. The dating of a bulk soil sample taken from the matrix of this unit indicates an age of 27.909 ± 400 cal a BP (Table 2).

Considering that the sample corresponds to a paleosol that has been reworked during the formation of UF, this age should be considered as prior to the formation of the wedge, that J o u r n a l P r e -p r o o f is: prior to the earthquake. This unit in turn is covered by UE, an alternation of 10 to 20 centimeters thick fine ashy deposits separated by some paleosol layers indicating relatively long periods between the different ash deposits (Fig. 4). A bulk soil sample taken from the thickest paleosol subunit gives an age of 5670 ± 64 cal a BP (Table 2). Next to the fault, UE is overlain by UD. Made up of angular to sub-angular blocks with a chaotic arrangement, UD has a characteristic wedge shape, whereby is interpreted as a colluvial wedge (Fig. 4) resulting from the erosion of the scarp formed during a surface rupturing earthquake, as observed in other case studies carried out in the region [START_REF] Langridge | Preliminary paleoseismic results from the Pastores fault and its role in the seismic hazard of the Acambay graben, Trans-Mexican Volcanic Belt, Mexico[END_REF][START_REF] Sunyé-Puchol | La falla San Mateo: Nuevas evidencias paleosismológicas de fallamiento activo en el graben de Acambay[END_REF]. Partially covering the wedge and UE, UC is formed by blocks in a clay matrix and interpreted as a slope deposit. On top of it, UB is composed of fine re-sedimented ash-fall deposit intercalated with clayish carbon rich paleosols. The dating of a bulk sample taken from one of these paleosols gives an age of 985 ± 65 cal a BP (Fig. 4 andTable 2). At the uppermost part, UA is rich in organic matter and corresponds to the present-day soil covering the surface on both sides of the fault.

Faulting history

The faulting geometry is almost the same in the four walls (Fig. 4). A 70 to 80º south dipping main fault with an E-W strike separates the volcanic basement, to the north, from the late Pleistocene to Holocene sedimentary filling to the south. UA is the only unit preserved on both sides of the fault and does not present any deformation of tectonic origin.

UB and UC are poorly preserved above the fault zone, but the displacement of unit B by a secondary synthetic fault is visible in trench 1-W. All the units deposited before UC are more clearly affected by faulting. Unfortunately, as most of the units are not preserved on either side of the main fault, it is not possible to determine the number of events and the associated displacements by measuring the displacement of the sedimentary units.

However, the presence of synthetic and antithetic structures to the main fault affecting different units and the preservation of colluvial wedges allows the identification of different paleoseismic events.

The most recent event (Ev. 3) can be identified on the walls of the two trenches, where antithetic and synthetic faults to the main one are cutting UD. In the western wall of trench J o u r n a l P r e -p r o o f 1 the F3 faults not only intersect UD but also UB, which is locally better preserved (Fig. 4).

However, the poor preservation of the units does not allow us to measure the coseismic displacement related to this event. The previous event (Ev. 2) corresponds to relatively large displacement along the main fault and to the formation of colluvial wedge 2 (UD).

Before this, the older event recorded in the trench (Ev. 1) is represented by colluvial wedge 1 (UF). Since the wedge is not completely exposed, we cannot estimate the slip per event.

Ev. 2 occurred contemporary or shortly before the formation of UD and Ev. 1 contemporary or shortly before the formation of UF. Note that UF, being only partially visible in the trenches, makes its interpretation as a colluvial wedge uncertain. Thus, this event is considered as hypothetical in the discussion chapter.

Discussion

Retrodeformation and chronology of the paleoseismic events

Based on the information collected in the Buenavista 1 and 2 trenches, two and possibly three paleoseismic events are interpreted. Through a retrodeformation analysis, the proposed sequence of rupturing and sedimentary events is summarized graphically. The tectono-sedimentary evolution of the trench can be divided into 5 main stages (Fig. 5):

1. During or shortly after a first seismic event (Ev. 1) associated with a surface rupture, the fault scarp is partially eroded and a colluvial wedge is formed at its base. Considering empirical relationship proposed by [START_REF] Mccalpin | Paleoseismology[END_REF] to estimate the size of the coseismic escarpment from the thickness of the colluvial wedge near the fault (> 40 cm), the topographic escarpment caused by the earthquake was likely greater than 80 cm. This first paleoseismic event has significant uncertainty since only the upper part of UF is visible in the trench and this unit could be interpreted differently. The dating of a bulk sample taken from a reworked paleosol indicates that UF was formed after 27.909 ± 400 cal a BP (Table 2).

2. After its formation, the colluvial wedge (UF) is eroded, reshaped and it is covered by deposits of ash interspersed with soils formed during periods of less volcanic activity (UE).

J o u r n a l P r e -p r o o f

A bulk sample taken from the thickest paleosol gives an age of 5670 ± 64 cal a BP for UE (Table 2).

3. A second earthquake (Ev. 2) with an approximate vertical displacement of 134 to 180 cm occurs a shortly after 5670 ± 64 cal a BP. This displacement is calculated based on the 67 to 90 cm thickness of the colluvial wedge formed by erosion of the scarp after the earthquake.

4. The erosion of the upper part of the relief causes the formation of slope deposits (UC) filling the depression formed at the toe of the scarp. All these previous units in turn are covered by an alternation of ash and soils (UB). A bulk sample taken from one of the paleosols gives an age of 985 ± 65 cal a BP for UB (Table 2).

5. Between the formation of UB and UA another earthquake (Ev. 3) must have occurred affecting UD and UB (only preserved above the fault zone in the 1 W trench). 6. Finally, the last stage corresponds to the current state in which UA, the current soil, covers all the units mentioned above.

Despite incomplete preservation of the tectono-sedimentary record and only few age datings in the Buenavista trenches, the age of the different seismic events is partially constrained. Ev. 1 is more hypothetical and we only know that it occurred after 27,91 ± 0,4 cal ka BP and before 5,67 ± 0,64 cal ka BP. Ev. 2 took place 5,67 ± 0,64 cal ka BP ago while the last earthquake, Ev. 3, occurred after 0,985 ± 0,065 cal ka BP and probably correspond to the sixteenth century Ameca earthquake.

Estimation of paleomagnitudes

The estimate of a paleoseismic event magnitude is a crucial factor in the evaluation of the seismic hazard [START_REF] Reiter | Earthquake hazard analysis[END_REF]. Different empirical relationships can be used in order to estimate paleomagnitudes from parameters such as surface rupture length (SRL) or vertical J o u r n a l P r e -p r o o f displacement (Dv). According to [START_REF] Stirling | Selection of earthquake scaling relationships for seismic-hazard analysis[END_REF], who compiled and reviewed these scaling relationships based on their relevance in a specific tectonic regime (e.g., plate tectonic setting, fault slip type, seismogenic thickness, lithology), the relationships proposed by [START_REF] Wells | New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement[END_REF] and [START_REF] Wesnousky | Displacement and geometrical characteristics of earthquake surface ruptures: Issues and implications for seismic-hazard analysis and the process of earthquake rupture[END_REF] are the most suitable in our case and will be used subsequently.

Since only the vertical displacement associated with event 2 is adequately constrained, the Dv related with this event will be used in order to estimate a paleomagnitude along this fault (average observed displacement: 1.65 m, maximum observed displacement: 1.80 m).

The results obtained from the empirical relations should be considered an approximation given that recent surface rupture shows great variability of vertical surface displacement along the scarp and accordingly, the poor representativity of isolated coseismic displacements measured at a given site along the scarp [START_REF] Ritz | High localization of primary slip zones in large earthquakes from paleoseismic trenches: Observations and implications for earthquake physics[END_REF][START_REF] Fletcher | Assembly of a large earthquake from a complex fault system: Surface rupture kinematics of the 4 April 2010 El Mayor-Cucapah (Mexico) Mw 7.2 earthquake[END_REF][START_REF] Suter | Comment on "Active Crustal Deformation in the Trans-Mexican Volcanic Belt as Evidenced by Historical Earthquakes During the Last 450 Years[END_REF][START_REF] Ritz | High localization of primary slip zones in large earthquakes from paleoseismic trenches: Observations and implications for earthquake physics[END_REF]. On the other hand, considering the complexity of the fault system, it is not possible to estimate, with only one trench site, if only one fault segment, the entire fault or various faults of the fault system ruptured during an event. In order to consider these unknowns, different scenarios of surface rupture length (SRL) must be considered (Fig. 6). The first one (sc. A) involves only part of the western segment and the totality of the central segment of the AAF with a total length of 35 km. Scenario B corresponds to a rupture length of 55 km along almost the whole AAF and scenario C to 70 km length rupture involving three segments of the Ameca -San Marcos Fault System (Fig. 6). This last scenario corresponds to the rupture suggested by [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF] based on the historical description in the "Relación de Ameca". The results of the paleomagnitude estimations for each scenario are summarized in Table 3. Following [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF], the westernmost branches of the AAF were not considered in the rupture scenarios. However, due to their short length, their inclusion or exclusion in the calculation of the possible magnitude has an influence of less than one tenth.

The magnitudes calculated from the SRL relations range between 6.8 ± 0.3 ≤ Mw ≤ 7.3 ± 0.3, while the one calculated from the maximum vertical displacement measured in the trench is 6.9 ± 0.1. All these results are of the same order of magnitude and indicate that major prehistoric seismic events occurred along this fault long before the sixteenth century Ameca earthquake. Nowadays, considering the high population density in the area, an J o u r n a l P r e -p r o o f earthquake of this magnitude could have disastrous consequences in terms of destruction and social impact.

The sixteenth century Ameca earthquake and the regional seismic hazard

This study provides geological evidence of recent seismotectonic activity along the AAF, which has generated at least two major earthquakes in the last 5000 years. The age of the last earthquake recorded in the trenches is not well constrained but probably corresponds to the historical Ameca earthquake. Based on historical documents, [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF] describes the Ameca earthquake as a 54-59 km-long rupture with associated vertical displacement between 1.67 and 3.34 m-high along the mountain front that separates the Ameca range from the plain (Fig. 6). Unfortunately, the displacement associated with this earthquake is not measurable in the trenches and the length of the surface rupture cannot be evaluated with the information reported at only one site.

These preliminary results attest to the persistent seismic activity of the fault system by geological means, providing a first estimate of paleomagnitudes and the paleo-earthquake chronology in the region. However, more trenches are necessary to confirm and complete the historical descriptions and interpretations of the Ameca earthquake. More paleoseismological studies will also clarify the relationship between the different fault segments and the possibility of multifault rupture events. The sedimentary record of surface ruptures reported here leads to estimates of a magnitude close to 7.0 for these events.

According to data from the Institute of Statistical and Geographical Information (IIEG) of the Jalisco government, in 2017 more than 5 million people lived in the megacity of Guadalajara, within a radius of 60 km from the AAF. Considering the important growth of the population and the poor-quality of the infrastructures, the hypothesis of a crustal earthquake with a magnitude ~ 7.0 would have catastrophic consequences. Although the probability of occurrence of such an event is low compared to a subduction earthquake, the expected damage could be comparable or greater; its shallow focal depth and its proximity to inhabited areas reduce the effectiveness of potential seismic early warning systems.

Moreover, historical or early instrumental events such as the 1920 Jalapa earthquake shows that even earthquakes of moderate magnitudes, statistically more frequent, can have equally J o u r n a l P r e -p r o o f disastrous consequences. Indeed, with only Mw 6.4, the Jalapa earthquake is the second deadliest earthquake in Mexico, only behind the 1985 subduction event [START_REF] Suárez | A Pioneering aftershock study of the destructive 4 January 1920 Jalapa, Mexico, earthquake[END_REF].

Accordingly, it is necessary to consider such shallow crustal sources in the seismic hazard evaluations in Mexico, as well as its implications for earthquake-resistant construction standards for the entire area affected by these faults.

In terms of interpretation of paleoseismic data, the increasing number of paleoseismological studies in the TMBV show the importance of working at the scale of the entire fault system to evaluate the seismic hazard. Indeed, the only two known historical events presenting associated surface ruptures in the TMVB correspond to complex multifault rupture events with associated magnitudes of 6.9 and 7.2 (e.g. The sixteenth century Ameca and the Acambay 1912 earthquakes; [START_REF] Suárez | Active crustal deformation in the Jalisco block, Mexico: evidence for a great historical earthquake in the 16th century[END_REF][START_REF] Suter | The Acambay graben: Active intraarc extension in the trans-Mexican volcanic belt, Mexico[END_REF][START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF]. Ignoring the possibility of a multi-fault rupturing event, the magnitude of potential earthquakes could be greatly underestimated considering that the longest faults in the TMVB rarely reach 50 km. In such a context, the number of trench sites relatively to the size and the complexity of the fault system should be better taken into account in the recently increasing number of proposals for estimating the paleoseismological uncertainty (e.g. [START_REF] Atakan | Seismic hazard in regions of present day low seismic activity: uncertainties in the paleoseismic investigations along the Bree Fault Scarp (Roer Graben, Belgium)[END_REF]Rodriguez-Perez et al., 2017).

Conclusions

In slow deforming regions where faults slip rates are of the order of or below 1 mm yr-1, earthquake recurrence intervals can reach thousands of years. For such low rates of deformation, geodetic techniques are usually not capable of detecting tectonic movements.

The time period covered by instrumental seismicity is not sufficient neither to describe the fault behavior nor to confidently estimate maximum magnitudes or fault segments involved. Still in many regions of the world, especially where long written records do exist, historical sources can significantly extend the knowledge on past seismicity and potential seismic sources. As a first result, two paleoseismic trenches excavated in the central segment of the Ameca-Ahuisculco fault, show evidence of its Holocene activity with two and possibly three paleo-earthquake ruptures. The older and less clearly defined recorded J o u r n a l P r e -p r o o f event, interpreted as a possible event, occurred after 27,91 ± 0,4 cal ka BP and before 5,67 ± 0,064 cal ka BP. The second one and best recorded occurred around 5,67 ± 0,064 cal ka BP and the last one occurred after 0,985 ± 0,065 cal ka BP and could correspond to the rupture of the sixteenth century Ameca earthquake.

Based on the vertical coseismic displacement calculated for the second event (180 cm), and different surface rupture length scenarios, maximum paleomagnitudes of 6.9 to 7.3 are estimated. This study presents preliminary but important results and underlines the difficulty of evaluating the size and length of a surface rupture and, the need of performing a more comprehensive paleoseismological studies on this complex and extensive fault systems.

Considering the estimated magnitudes and the complexity of the fault system, the Ameca-Ahuisculco fault is an important seismic source of the TMVB, capable of generating destructive earthquakes with magnitudes ~ 7. Although the frequency of occurrence of large crustal earthquakes is low compared with subduction earthquakes, such a possibility has to be considered in seismic hazard assessment in central Mexico region, where most of the Mexican population is concentrated. Therefore, it is particularly important to better evaluate the possibility of occurrence of multifault rupture events within the TMVB by increasing the number of paleoseismological studies. [START_REF] J O U R N A L P R E -P R O O F Suárez | Active Crustal Deformation in the Trans-Mexican Volcanic Belt as Evidenced by Historical Earthquakes During the Last 450 Years[END_REF][START_REF] Zúñiga | Temporal and spatial evolution of instrumented seismicity in the Trans-Mexican Volcanic Belt[END_REF]. (B) Zoom on the Ameca-San Marcos Fault System. The red lines represent the faults that presumably ruptured during the sixteenth century Ameca earthquake according to [START_REF] Suter | The A.D. 1567 Mw 7.2 Ameca, Jalisco, earthquake (Western Trans-Mexican volcanic belt): Surface rupture parameters, seismogeological effects, and macroseismic intensities from historical sources[END_REF]. Current soil UB 38 to 80 cm of alternation of light ashy layers with brown and orange tones and dark clay layers. The ashy layers are characterized by the presence of lithics with a high degree of weathering and clay minerals due to the alteration of plagioclase. Lithics are sub-rounded to subangular with sizes ranging from 7 mm to 6 cm. The iron oxides and mafic minerals are present in a smaller proportion. The brown clay layers is carbon rich and reaches 8 cm thick.

Re-sedimented ash fall deposit interspersed with layers of paleosols

UC

Mainly andesitic clasts with different degrees of alteration and oxidation in a dark clay aphanitic matrix. The clasts are subangular to subrounded in shape with poor classification and variable size between 2 and 60 cm. The unit's thickness varies from 12 to 52 cm.

Slope deposits

UD

Mainly subangular andesitic clasts and blocs without preferential direction in a fine size sandy to clayey matrix. This unit draws a wedge shape, thick near the fault plane and thinner further. Colluvial wedge 1

UG

Located in the footwall of the two trenches, this unit consist in andesitic to dacitic blocks of any size embedded in a hardened and weathered ashy matrix with dark yellow to orange hue, rich in quartz and in products of alteration of plagioclase, which increase when approaching the fault plane.

Pyroclastic flow of blocks and ash

Table 1: Sedimentary description and genetic interpretation of units exposed in the trench walls.

J o u r n a l P r e -p r o o f

Figure 1 .

 1 Figure 1. (A) Main tectonic features and historical seismicity Map of the TMVB. Black lines indicate different fault systems and the red stars the main historical seismic events (Modified from[START_REF] J O U R N A L P R E -P R O O F Suárez | Active Crustal Deformation in the Trans-Mexican Volcanic Belt as Evidenced by Historical Earthquakes During the Last 450 Years[END_REF][START_REF] Zúñiga | Temporal and spatial evolution of instrumented seismicity in the Trans-Mexican Volcanic Belt[END_REF]. (B) Zoom on the Ameca-San

Figure 2 .

 2 Figure 2. (A) Morphological map of the Ameca-Ahuisculco fault system. The colored numbers represent the scarp heights (in meters) measured in each sub-segment. (B) Geological map of the same area showing the rocks affected by the fault (modified from Ferrari et al., 2018).

Figure 3 .

 3 Figure 3. (A, B, C) Aerial photograph of the AAF near the Buenavista trench site (from Google Earth). The insets in A and B correspond to areas shown in B and C.

Figure 3 (

 3 Figure 3 (continued). (D) 3D view of the escarpment at Buenavista trench site (from Google Earth), (E, F) field photographs of the trenches showing the difference of vegetation on both side of the fault.

Figure 4 .Figure 5 .

 45 Figure 4. Logs of the Buena vista trenches. See Table1and text for the description of the units. Eastern walls of the trenches are flipped for ease of comparison. At the bottom, zoom of the fault zone of the trench 1-W. Photomosaics in supplementary material.

Figure 6 .

 6 Figure 6. Rupture scenarios proposed for estimate the paleomagnitudes. WAAF: Western Ameca-Ahuisculco Fault, CAAF: Central Ameca-Ahuisculco Fault, EAAF: Eastern Ameca-Ahuisculco Fault, VCF: Villa Corona Fault, SMF: San Marcos Fault. In red: rupturing fault, in yellow: non-rupturing fault.

  with abundant organic matter. Thickness from 40 to 53 cm. Some andesitic to dacitic sub-rounded clasts are dispersed without any particular organization.

  cm of alternation of yellow ashy layers and darkbrown clay layers. Some millimetric to centimetric mafic clasts and obsidians are scattered in the ashes. They are smaller towards the top and larger towards base. The clay layer reaches 14 cm thick.Ash fall deposit with an intermediate paleosolUF32 cm of angular clasts of varied composition, poorly classified, with a chaotic disposition and violet hue due to oxidation in a brown to orange matrix. This last is quite heterogeneous and relatively consolidated in some part.

Table captions Table 1 :

 captions1 Sedimentary description and genetic interpretation of units exposed in the trench walls.

Table 2 :

 2 Dating results. Samples processed by the LMC14-CEA Saclay laboratory, GIF sur

	Yvette, France. The calibrated ages have been obtained using OxCal 4.2 software (Bronk
	Ramsey, 2009).

Table 3 :

 3 Magnitudes calculated with the empirical relationships of Wells & Coppersmith

Table 2 :

 2 Dating results. Samples processed by the LMC14-CEA Saclay laboratory, GIF sur Yvette, France. The calibrated ages have been obtained using OxCal 4.2 software[START_REF] Bronk Ramsey | Bayesian analysis of radiocarbon dates[END_REF].

	Sample name	Type of	Radiocarbon age	Calibrated age	Calibrated
	(Unit)	sample	(yr BP)		age (Yr. Cal.
					BP)
	TBV-M-5 (UB)	Soil (Bulk)	1045 ± 30	965 ± 65 cal. AD	985 ± 65
	TBV-M-4 (UE)	Soil (Bulk)	4950 ± 30	3721 ± 64 cal. BC	5670 ± 64
	TBV-M-3 (UF)	Soil (Bulk)	23750 ± 210	25960 ± 400 cal.	27909 ± 400
				BC

J o u r n a l P r e -p r o o f

Table 3 :

 3 Magnitudes calculated with the empirical relationships of Wells & Coppersmith

Acknowledgments

This work was supported by the Universidad Nacional Autónoma de México [PAPIIT grant IA102317, IN108220 and IN109819]. Dating were performed at the LMC14 laboratory of Saclay and Gif-sur-Yvette, France (J.-P. Dumoulin). Radiocarbon dates were obtained thanks to IRD support Audin L. in the frame of the French "Institut de Recherche pour le Développement" collaboration. We acknowledge the Master scholarship grant to the first author from CONACYT-Mexico. We thank the Master scholarship grant and the mobility scholarships to the first author from CONACYT-Mexico. We thank Sandra Lorena Florez Amaya for field assistance and the owners of the paleoseismological sites for their permissions. This manuscript was greatly improved by comments and suggestions from Gerardo Suárez and Hans Diederix.

J o u r n a l P r e -p r o o f

Highlights:

-Largest active fault system described and characterized near Guadalajara, Jalisco.

-First geological evidence of sixteenth century Ameca earthquake -Undocumented prehistorical earthquakes identified for the first time along the Ameca-Ahuisculco fault.

-Paleoseismology completes the catalog of historical seismicity and contributes to a better evaluation of the seismic hazard. The roles of the authors were as follows: Núñez Meneses: master student, this study was the subject of his master's research work, formal analysis, writing. Lacan: Project leader, conceptualization, supervision (thesis director of Andres), leader of fieldwork, data processing, resources, writing. Zuniga: field assistant, manuscript review and comments, resources. Audin: Dating of samples, data processing, manuscript review and comments. Ortuño: Data processing, manuscript review and comments. Rosas Elguera: field assistant, manuscript review and comments. Leon-Loya: field assistant, manuscript review and comments Márquez: field assistant The manuscript and figures have been prepared in accordance with the guidelines for authors provided on the South American Earth Sciences webpage.

Sincerely yours, Dr. Pierre Lacan Investigator Titular A Centro de Geociencias UNAM, México J o u r n a l P r e -p r o o f

Declaration of interests

☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:


Nicolas M Charpentier
email: nicolas.charpentier2@cea.fr

Ange A Maurice

Dong Xia

Wen-Jie Li

Chang-Sian Chua

Andrea Brambilla

Jean-Christophe P Gabriel
email: christophe.gabriel@cea.fr

Urban Mining of Unexploited Spent Critical Metals from E-waste Made Possible Using Advanced Sorting

Keywords: Recycling, Waste PCBs, computer vision, Multi-energy X-ray Transmission, hyperspectral imaging, waste management

The growing number of electronic devices has led to a surge in e-waste, making efficient recycling essential to reduce environmental impact and recover valuable metals. However, traditional recycling methods struggle to extract them due to their low concentrations in ewaste. Here, we developed a system to sort electronic components from printed circuit boards by elemental composition. It combines a convolutional neural network-based optical recognition with multi-energy X-ray transmission spectroscopy, demonstrating up to 96.9% accuracy in controlled conditions. Hence, with elemental enrichments by up to 10,000 for targeted elements, this method renders economically viable the recovery of previously unrecycled critical metals by enriching sorting bags in precious, semi-precious, refractory (Ta, Nb), transition (Co, Cr, Mn, Ni, Zn, Ga, Bi, etc.) or other (In, Sn, Sb) metals. These findings demonstrate the promising applications of this technology in mitigating the environmental impact of e-waste and promoting the sustainable recovery of valuable metals.

INTRODUCTION

33 The technological development and the 34 automation of our modern society is 35 supported by an exponential increase in 36 our use of electronics, which leads to a 37 similar increase in the amount of waste 38 from electrical and electronic equipment 39 (WEEE) (Forti et al. 2020). 40 Manufacturing these devices requires a 41 considerable volume of raw materials 42 including valuable ones (gold, palladium, 43 silver…), critical elements (rare earth 44 elements (REEs) (Binnemans, 45 McGuiness, and Jones 2021), tantalum, 46 cobalt…) as well as hazardous products 47 (lead, chromium, bromine…) (Wang and 48 Xu 2015). Thus, making the electronic 49 industry (considered from cradle to cradle) 50 one of the most environmentally 51 impacting (Shakil, Nawaz, and Sadef 52 2023). 53 A good way to reduce this industry's 54 footprint would be to increase the 55 efficiency of its recycling processes. But 47 2022). So far, these methods have been 48 limited to only a few EC categories, 49 giving access to only a few more chemical 50 elements. Other processes have privileged 51 a selective robotic disassembly (pick and 52 choose approach), which requires high 53 precision for removing the targeted ECs. 54 However, with a speed of a few tenths of a 55 second per component retrieved, it can 56 only be applied to high value ECs to be 57 economically viable (Sauer et al. 2019). 58

for this to happen, the major issue of the 1 elemental complexity of the WEEEs' 2 composition needs to be addressed. On

MATERIALS AND METHODS

Materials

For this study, model ECs from various 17

The powder prepared was then analysed

Process validation

For The first sorting step based on optical sorting showed a global accuracy of 97.4 % for a total of 8 categories (Table SI 2, Table SI 3 andTable SI 4

Throughput and process industrial implementation

This sorting process presents a great opportunity for the development of economically viable processes. The viability of this process was previously reported by [START_REF] Xia | S i ble R e f r Nd Recycli g fr m W e Elec r ic mp e Fe red wi h Unique Element-Specific Sorting Enabling Simplified Hydrometall rgy[END_REF]) in the study of neodymium from Nd-based SLCC. Although this study only considered the recovery of Nd-based SLCC, the process was already showing a payback time of less than 5 years. While other recycling processes targeting specific ECs have been developed [START_REF] Chen | Selec ive Rec very f Preci Me l hr gh Ph c ly i[END_REF]Niu and Xu 2018;Wang and Xu 2017), they often lacked a mean of obtaining concentrated streams of the targeted ECs. This sorting process addresses this issue by effectively classifying and separating ECs, allowing for the recovery of valuable materials in a concentrated form. The ability to recover these materials in a concentrated form significantly improves the economic viability of the recycling process. This technology has the potential to revolutionise the field of electronic waste management and recycling by providing an efficient and cost-effective method of recovering valuable materials from discarded electronic components. However, the limitations of the process lie in the in-line treatment of the ECs, and the sorting speed will be improved in further development of the prototype by using a parallel sorting. We developed a demonstrator at a laboratory scale to validate the feasibility of advanced sorting and its compatibility with industrial plants by testing the sorting capability as a function of belt speed, although a larger, multi-lane industrial sorting tool would use similar conveyor speed. The cost of the prototype was broken down as follows: 50,000 USD for the X-ray system (generator, detector, shielding), 2,500 USD for the control and data acquisition systems, and 12,500 USD for the mechanical structure, conveyor belt and sorting system. It is important to note that the costs of a laboratory-scale prototype may not be directly transferable to a larger, multi-lane industrial sorting tool. On a 1 meter large conveyor belt, up to 50 ECs can be treated in parallel. Thus, the sorting speed of the prototype would be multiplied by fifty allowing the sorting of up to 500 kg/h. Considering that a country such as Singapore produces an average of 60000 tonnes of e-waste per year, resulting in approximately 1620 tonnes of ECs ( PCBs represent 6 wt.% of the global e-waste (Pinho, Ferreira, and Almeida 2018)), 3240 machine hours would be required, equivalent to 125 days. Hence, this process shows promising results for industrialisation.

Conclusion

In conclusion, our instrumental developments and integration reported here presents a highly effective sorting process for electronic components (ECs) that combines physical, optical and MEXRTbased tools and process steps. The overall process is capable of concentrating valuable chemical elements in the final streams with, for example, an enrichment of up to 10,000 times its initial content in the WPCBs in the case of gold, including metals that are currently wasted and not recovered in industrial recycling settings. Achieving such levels of enrichment, while combining high accuracy and low operating costs, opens up new opportunities in the recycling industry, especially regarding these elements that are lost in WEEE recycling processes. Indeed, such elementally enriched fractions can either be traded or purified by hydrometallurgy. In the latter case, one still has to face the issue of the variability of the composition of the sorting bags, which can be solved thanks to state of the art microfluidics based rapid process development tools [START_REF] Maurice | First Online X-ray Fluorescence Characterization of Liquid-liquid Extraction in Microfluidics[END_REF][START_REF] Olivier | Liq id-Liquid Extraction: Thermodynamics-Ki e ic Drive Pr ce e Expl red by Micr fl idic[END_REF][START_REF] Olivier | O -Line Quantification of Solid-Ph e Me l Ex r c i Efficie cie U i g I r me ed Millifl idic Pl f rm[END_REF].

Credit

3(

  that front, printed circuit boards (PCBs)4 Gorewoda et al. 2020), hold the record 5 with more than sixty chemical elements 6 that can be found in them(Maurice et al.

((

  approach, although 60% of the 17 value can be retrieved from the WPCBs, it 18 only recycles one quarter of the chemical 19 elements it contains, either the most 20 concentrated or the most valuable (C, Cu, 21 Ni, Fe, Al, Ti, Cr, Au, Pt, Ag, Pd, Pb, Sn) intelligence (for 43 example, convolutional neural network -44 CNN). The latter has shown promising 45 results for the classification of ECs 46 Tan et al. 2022). However, all these 89 approaches can only analyse the surface 90 composition of ECs and do not capture all 91 the internal chemical composition and 92 elements. For this reason, these are useful methods for the characterisation and sorting of homogeneous or monolithic materials such as plastics. To get access to some internal composition indication, few energies (one to five) X-ray transmission (XRT) spectroscopies have been used in a variety of fields such as mining (Veras et al. 2020; Yeyu et al. 2021), food industry, medical imaging (Mesina, de Jong, and Dalmijn 2007) or even plastic waste sorting (Hennebert and Filella 2018), but these approaches do not have enough energy resolution to allow for the elemental sorting of mixture as complex as wasted electronic components from WPCBs. Hence, this study where we present a novel sorting method for ECs using both optical and Multi-Energy XRT (MEXRT) sorting (up to 128 energy levels) in which ECs were sorted on a custom-made prototype using a CNN for image recognition followed by MEXRT hyperspectral image spectroscopy analysis. We will show that it allows for the accurate classification of ECs based on their type and elemental composition leading to such an enrichment in many targeted elements, so as to provide access to previously unrecoverable spent elements.

Figure 1

 1 Figure 1: a) Photograph of the whole prototype, close view of the bowl feeder, c) close view of the camera and light and d) 3D CAD view of the prototype

Figure 2 :

 2 Figure 2: Mass distribution of the components in different size sub-fractions and their corresponding pictures Given these limitations, the subsequent sorting steps performed in this study focused on the three fractions of ECs with sizes comprised between 1 and 40 mm. Overall, the results of the sieving step showed that the system was able to efficiently and accurately separate the ECs into these different size categories, with 35 wt.% of the components falling within the target size range for further analysis. Fourteen different types of ECs with chemical compositions of interest were identified as the most common, of which, between five to nine of them could be found in the different size fractions, therefore already significantly reducing the heterogeneity of the ECs for the subsequent sorting steps. The distribution of the ECs by category can be

Figure 3

 3 Figure 3: a) Spectra extraction from hyperspectral images and b) elements k-edge recognition.

  ). The accuracy of the sorting process was evaluated by monitoring the number of ECs in the final bins, taking into account both the optical classification and the mechanical diversion of the different ECs into their respective sorting bins. With a minimum accuracy of 92.5 % for CPUs. This is to be compared to the current state of the art in optical sorting, which achieved a maximum of six EC categories with 98 % accuracy on their own training datasets, which could only give access

Figure 4 :

 4 Figure 4: Flowchart of the sorting process for ECs The optical sorting process can reach a speed of 0.014 s/EC using a camera at a speed of 75 frames per second. The MEXRT acquisition speed used was 2 ms per line acquired and 50 lines of 0.8 mm were acquired for a total acquisition of 40 mm, resulting in a maximum sorting speed of 0.1 s/EC. Considering the data processing of the different images, with the PC configuration used in this study, the sorting speed for optical sorting was reduced to 0.017 s/EC and 0.15 s/EC for the MEXRT sorting (approximately 59 ECs/s and 7 ECs/s respectively). The image pre-processing method efficiently defines the region of interest using only a minimum transmission finding, allowing accurate EC localization even for lowdensity materials, the only issue being the detection of multiple ECs on the same image, which is outside the scope of this study. To ensure that consecutive components are not too close to each other during the MEXRT acquisition, a safety distance corresponding to at least one

  90

Figure 5 :

 5 Figure 5: Mass flow diagram for the up-scaled process

Figure 6

 6 Figure 6: a) entropy of metals and b) number of elements in the different sorted categories. All chemical elements present in the major elements fraction (blue blocks) are listed in white. Significant elements that where either at trace level or below

  the next sorting steps, we first

			43
			44	SI 1) as the most common found in PCBs,
	35		45	which furthermore contained targeted
	36	evaluated the performance of a sorting	46	rarely recycled critical elements such as
	37	approach consisting of an initial optical	47	Nd, Ta, Nb, Pd in capacitors, gold in
	38	sorting followed by MEXRT imaging. In	48	CPUs/connectors	or	aluminum	in
	39	order to validate such a process and		electrolytic aluminum capacitors. IC chips
		evaluate its performance, a model sample

40 made of a controlled mixture of ECs was 41 prepared for each size sub-fraction.

42

Fourteen EC types were identified (Table

  This is the case for single

	32
	33	layer capacitors (SLCC), which can be
	34	divided into 4 categories: barium-based
	35	SLCC,	non-barium-based	SLCC,
	36	neodymium-rich barium-based SLCC and
	37	tantalum capacitors (Figure 4). The same
	38	applies to MLCCs, which can be divided
		into two main categories: barium-based

39

MLCCs and non-barium-based MLCCs. 40 By using the transmittance of the ECs, 41 XRT spectroscopy can easily separate 42 relays from metallized polymer capacitors 43 (MPCs) with 100 % precision which could 44 not be done based solely on the ECs' 45 features using optical sorting (Table SI 5, 46 Table SI 6 and Table SI 7).

  ). Any fraction with

			33	contained up to 47.04 wt.% of tin (Table
			34	SI 8).
	16 17 18 19 20 21 22 23 24 25 26 27 28 29 31 32	an entropy lower than the latter, can be said to have a simpler composition. This comparison shows that all fractions have a significantly lower entropy than the one of the ground WPCB. This reduction of the entropy of the phase is particularly visible for inductors and relays, which are mainly composed of iron and copper. In the cases with the highest entropy, such as the category labelled "5-1 mm other SLCC", this level of entropy comes from the sorting induced enrichment in Mn, Zn and Bi, that are now no longer present in traces, and therefore significantly contribute to the entropy. Same goes for the MPCs sorting bin, which after sorting	35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51	Overall, looking at Figure 6-b and comparing the number of major elements present either in the initial WPCB or in each of the sorting bins, it can be seen that all the sorted categories have much simpler composition, especially when only considering the number of major elements in their composition (all have less than six elements with concentration over 1 wt.%, to be compared to thirteen in the original WPCB). This demonstrates that the process is not only effective in separating and classifying electronic components, but it also easily and effectively concentrates valuable metals, thus facilitating subsequent chemical separation, a key requirement for making their recycling economically viable.

  (at WPCB level) but could be enriched during the process to the level of "Minor elements", are indicated in grey over the orange blocks.

	a) the detection limits
	b)
	Al Cu Fe Fe Al Cu													RE RE
	Si Sn Ni Sb O Ca Pb Zn C Br Si Sn Ni Sb O Ca Br Pb Zn C	Fe Fe	Fe Cu Sn Al Fe Cu Sn Al	Ca Al Ca Al	Fe Cu Sn Fe Cu Sn	Cu Sn Fe Cu Sn Fe	Cu Au Cu Au	Cu Au Cu Au	Cu Fe Mn Cu Ta Cu Cu Ta Fe Mn	Sn Zn Bi RE Es Sn Zn RE Es Bi	Cu Al Cu Al	Fe Al Sn Ca Cu Fe Al Sn Ca Cu	Sn Fe Pd Cu Sn Fe Pd Cu	Cu Ca Ba Bi Ni Sr Es Cu Ca Ba Es Bi Ni Sr Pb	Fe Ni Sn Cu Ni Sn Cu	Sn Cu Fe Ni Sn Cu Ni	Sb Cu Fe Sn Pb Mn Sb Sn Mn	Ba Cu Sn Ni Pd Pb RE Es Ba Sn Ni RE Es Pd Pb

  Declaration of Competing InterestNMC and JCG wish to declare that MEXRT detector ME100 used in the work described here is commercialised by Detection Technology under patent licensing from CEA. The authors declare no other competing interests.

	authorship		contribution
	statement
	Nicolas	M.		Charpentier:
	Conceptualization,		Methodology,
	Software, Investigation, Data curation &
	Interpretation, Writing-Original draft
	preparation.	Ange	A.	Maurice:
	Conceptualization,		Investigation,
	Reviewing and Editing. Dong Xia:
	Investigation,	Data	curation	and
	Interpretation, Writing-Reviewing and
	Editing. Wen-Jie Li: Investigation.
	Chang-Sian Chua: Investigation. Andrea
	Brambilla: Conceptualization. Jean-
	Christophe P. Gabriel: Conceptualization,
	Methodology, Data Interpretation, Writing-
	Reviewing and Editing, Supervision,
	Funding	acquisition,		Project
	administration.

Acknowledgement All authors acknowledge financial support from SCARCE project, which is supported by the National Research Foundation, Singapore, and the National Environment Agency, Singapore under its Closing the Waste Loop R&D Initiative (Award No. USS-IF-2018-4) and Closing the Resource Loop Funding Initiative (Award No. CTRL-2022-1D-01). NC acknowledges financial support (salary) in 2023 by the REVIWEEE project grant managed by the French National Research Agency (ANR) under the France 2030 programme, award No. ANR-22-PERE-0009.

The sorting process results were then


Régis Hocdé
email: regis.hocde@ird.fr-gerard.thouzeau@univ-brest.fr

Gérard Thouzeau

Sophie Bourquin

Laurent Borel

Mathieu Coulange

Jean-Pierre Féral

Éric Feunteun

Stéphan Jacquet

Philippe Le

Le Bras

Le Gall

Scientific diving in France: an overview of the current practices in science

de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The FRENCH NATIONAL COMMITTEE for SD PROFESSIONAL CERTIFICATIONS

OCEANOGRAPHIC SUPPORT VESSELS FRENCH OVERSEAS TERRITORIES & ABROAD

The French National Committee for Scientific Diving (CNPS) is a key actor for developing occupational scientific diving in France (Thouzeau et al., 2019). This inter-agency committee on occupational scientific diving created in 1999 involves:

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… AND VARIOUS ECOSYSTEMS

Due to the existence of overseas territories -with France's maritime spaces representing the world's second largest exclusive economic zone -French territories display an extensive variety of submarine habitats. Furthermore, the historical richness of scientific diving in France has led the French scientific diving community to be involved in all oceans worldwide. All subaquatic ecosystems, from the polar regions to the tropical belt, from drowned karsts to freshwater and high altitude lakes, including mesocosms and artificial structures are studied by diving scientists.

In light of the diversity of environments, disciplines and scientific topics/fields, scientific divers are continuously innovating to perform outstanding research.

On top of the traditional diving methods (open circuit, hookah and apnea) scientific diving benefits in recent years from the use of closed-circuit rebreathers but also from combining CCR and saturation methods, which greatly enhanced the study of the mesophotic zones.

France participates significantly in this demonstration of the essential usefulness of occupational scientific diving to the realization of works published in scientific journals with high impact factor (>5) (source: SD supported articles in IF>5′ journals (sorted by date) -esdpanel.eu).

The French occupational scientific diving community, a very diversified population due to:

1. France's 18,000 -km -long coastlines and a strong presence overseas 2. The involvement of researchers in global science topics/fields from the poles to tropics.

University courses and summer schools train scientists and prepare for professional diving qualifications (on top of CAH).

The oceanographic vessels of the French Oceanographic Fleet research infrastructure (FOF RI) can be used to support scientific divers, as well as the scientific vessels of DRASSM (the French Department of Underwater Archeological Researches). Some private ships are also chartered.

Phymarex is a non-profit association with the aims to preserve health and optimize safety in maritime and extreme environments. It gathers doctors, medics, paramedical staff, researchers and people with an active contribution or a particular interest in the field of medicine and physiology in maritime environments, in isolated environments and in unusual physiological conditions.

  Fig 1.a: The French overseas departments and regions with the maritime zones ; 1.b The French network of 16 universities in marine sciences (representing France at the European Marine Board) (blue dot) and the 3 marine stations of EMBRC France (yellow dot).

  16 French marine universities : Aix-Marseille, Bordeaux, Brest, Marseille, Lorient, Caen, La Rochelle, Lille 1, Dunkerque (ULCO), Montpellier, Nantes, Nice Sofia-Antipolis, Perpignan via Domitia, Sorbonne Université (Paris), Toulon, Toulouse III, Le Havre -11 research institutes: CNRS-INEE/INSU/INSHS, DRASSM, EPHE, IFREMER, INRAE since 2020 (former INRA + IRSTEA that decided to join), INSERM, IPEV, IRD, MNHN -1 medical research Centre specialised in hyperbaric medicine -Personalities chosen for their expertise in the field of professional scientific diving. The CNPS takes on different tasks including acting as an observatory of occupational scientific diving practices and innovations. The aims are to: -ensure a scientific watch on the evolution of the professional scientific diving practices worldwide -monitor/follow the innovations in scientific diving, technology, field practices and hyperbaric medicine -define common frameworks and promote the best practices -share information and feedback with the French scientific diver community -participate in the training of vocational scientific divers -represent France at the European Scientific Diving Panel (ESDP) -provide high-level expertise and advices to the Ministries of Labour and Higher Education and Research Since 1991 in France, scientific diving has been recognized by law as an occupational sector and is therefore regulated with the aim to reduce the hyperbaric risk and facilitate mobility of scientist thanks to standards. Professional diving certifications are required to practice in France (to be recycled every 5 years): -around 10,000 certified divers CAH mention B (scientific and archaeological diving) issued since 1991 (source: DGT/Ministry of Labour) -with depth classes (CAH 0: < 12m, CAH 1: < 30m, CAH 2: < 50m, CAH 3: up to 100 m depth) -Note: Professional divers from industry have CAH mention A ALL DISCIPLINARY FIELDS… Currently, French scientific diving encompasse many fields such as life sciences and ecology, geosciences, social & cultural sciences including archeology, health & food, engineering sciences, energy...

Several

  French teams (academic, or joint public-private consortiums) explore the mesophotic zone and organize scientific expeditions in France and abroad (LENGGURU Expeditions & IJL SELAMAT / IRD, Planète Revisitée / MNHN, GOMBESSA Expeditions / Laurent Ballesta / Andromède Océanologie, Under The Pole...). Several SD training modules offered by CEFREM in three Master's Degrees © G. Saragoni CEFREM © Phymarex ANTEA oceanographic vessel © IRD -JM Boré Alfred Merlin scientific vessel © P. Soubias DRASSM a) Inventory of cryptic benthic species -La Planète Revisitée expedition in Corsica (2019-2021) © MNHN, b) Underwater archaeological operation of Olbia de Provence. Operation leader L. Borel © L. Roux (CNRS, CCJ), c, d) SD activities of LEMAR © E. Amice CNRS, e) Freediving verification of the UROS project structure (RECOBER) © INRAE, f) Maintenance of optodes in the ponds of the Aquitaine coast (EABX, INRAE Cestas) © INRAE, g) Exploration of Papuan karsts, Indonesia -LENGGURU © G. Dimaimondo IRD, h) Projet CHAMAUT, Mediterranean coastal lagoons © R. Hocdé IRD, i) Photogrammetry, and ecology of submarine landscapes. Plateau des Roches Douvres © V. Danet MNHN Dinard, j) Study of the Guyanese mangroves, ANR BIOMANGO © G. Thouzeau LEMAR k) Sampling of water from the benthic chamber to analyze its acidity (Ph) © Laurent Ballesta / Expéditions Gombessa / Andromède Océanologie l) Bathyal Station © Laurent Ballesta / Expéditions Gombessa / Andromède Océanologie, m) Long-term observatory of the mesophotic zone by environmental DNA, Calanques, France, Labcom DIAGeDNA/DeepHeart Project © R. Hocdé IRD, n,o) Mesophotic Coral Ecosystems study in Indonesia -LENGGURU © E. Bahuet, G. Diraimondo IRD