Search

We present a database of field data for active faults in the central Apennines, Italy, including trace, fault and main fault locations with activity and location certainties, and slip-rate, slip-vector and surface geometry data. As advances occur in our capability to create more detailed fault-based hazard models, depending on the availability of primary data and observations, it is desirable that such data can be organized in a way that is easily understood and incorporated into present and future models. The database structure presented herein aims to assist this process. We recommend stating what observations have led to different location and activity certainty and presenting slip-rate data with point location coordinates of where the data were collected with the time periods over which they were calculated. Such data reporting allows more complete uncertainty analyses in hazard and risk modelling. The data and maps are available as kmz, kml, and geopackage files with the data presented in spreadsheet files and the map coordinates as txt files. The files are available at: 10.1594/PANGAEA.922582., Measurement(s) active geological fault Technology Type(s) digital curation Factor Type(s) location Sample Characteristic - Environment geological fault Sample Characteristic - Location Central Apennines Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14102021

Long-term landscape evolution is controlled by tectonic and climatic forcing acting through surface processes. Rivers are the main drivers of continental denudation because they set the base level of most hillslopes. The mechanisms of fluvial incision are thus a key focus in geomorphological research and require accurate representation and models. River incision is often modeled with a stream power model (SPM) based on the along-stream evolution of drainage area and channel elevation gradient but can also incorporate more complex processes such as threshold effects and statistical discharge distributions, which are fundamental features of river dynamics. Despite their importance in quantitative geomorphology, such model formulations have been confronted with field data only in a limited number of cases. Here we investigate the behavior of stochastic-threshold incision models across the southeastern margin of the French Massif Central, which is characterized by significant relief and the regular occurrence of high-discharge events. Our study is based on a new dataset combining measurements of discharge variability from gauging stations, denudation rates from 34 basins from 10Be cosmogenic radionuclide (CRN) concentration measurements in river sediments, morphometric analysis of river long profiles, and field observations. This new dataset is used for a systematic investigation of various formulations of the SPM and to discuss the importance of incision thresholds. Denudation rates across the SE margin of the Massif Central are in the 20–120 mm kyr−1 (equivalent to mm/ka in the figures) range, and they positively correlate with slope and precipitation. However, the relationship with the steepness index is complex and supports the importance of taking into account spatial variations in parameters (D50, discharge variability k, runoff) controlling the SPM. Overall, the range of denudation rate across the margin can mainly be explained using a simple version of the SPM accounting for spatially heterogeneous runoff. More complex formulations including stochastic discharge and incision thresholds yield poorer performances unless the spatial variations in bedload characteristics controlling incision thresholds are taken into account. Our results highlight the importance of the hypotheses used for such a threshold in SPM application to field studies and notably the impact of actual constraints on bedload size.

(IF 4.45: Q1); International audience; The emerged coral reef terrace sequence at Cape Laundi, on the north coast of Sumba Island (Indonesia), with at least 18 successive strandlines, remains poorly dated in spite of numerous previous data. The age discrepancies within these coral reef terraces (CRTs) were previously explained by their polycyclic nature, triggered by marine erosion and reoccupation of old coral colonies by new ones. This study aims at highlighting these processes, as well as the continental denudation that participates in the partial stripping of the thin superficial coral reef layer overlying the pre-existing surface, exhuming older coral colonies. For this purpose, we use a combined analysis of 36Cl cosmogenic concentrations, new 230Th/U ages, and previous dating in order to quantify denudation rates affecting the sequence and to highlight the role of marine erosion in reworking the lowest CRT surface. Our results demonstrate that 1) the lowermost CRT is composite, i.e., formed by different reefal limestone units constructed and eroded during successive highstands of the last interglacial, 2) following the last deglaciation, this CRT has been subjected again to coastal erosion and reoccupation during the Mid Holocene highstand, 3) its distal edge is affected by the current marine erosion and shows denudation rates higher by one to two orders of magnitude (from 279 ± 0.4 to 581 ± 0.4 mm ka−1) than the continental denudation values of higher CRTs (14.7 ± 8.3 mm ka−1 on average), 4) at the scale of a single CRT surface, variations in continental denudation rates are caused by epikarstification roughness, and 5) the distal edges have the highest continental denudation rate due to diffusion and regressive erosion produced by the runoff occurring along the steep downward cliff.

International audience; The footwall of the surface rupturing Paganica normal fault, the source of the 2009 L'Aquila earthquake (Mw 6.1) in the Central Apennines (Italy), was investigated using integrated geological and geomorphological approaches. The aim was to constrain the active tectonics by studying the Raiale River that orthogonally crosscuts the fault trace, where it provides a useful geomorphological marker of long-term fluvial incision and footwall uplift. Using morphostratigraphy and paleomagnetic analysis, the Plio-Pleistocene morphotectonic evolution of the area was reconstructed, comprising an ancient continental basin and paleolandforms that predate the footwall incision. Starting from the Late Early Pleistocene-Middle Pleistocene, fluvial dissection was mainly due to marked river downcutting triggered by significant activity of the Paganica Fault, which caused progressive base-level lowering. The Raiale River downcutting formed five Middle-Late Pleistocene fluvial terraces, that, along with absolute Optically Stimulated Luminescence (OSL) dating, allowed the identification of paleolongitudinal profiles with a diverging downstream configuration. Terrace dating yielded a minimum incision rate of 0.25 ± 0.02 mm/a, which only partially compensates the footwall uplift and can thus be considered as a minimum value for the Paganica Fault throw rate, which could reach up to ~0.45 mm/a. In parallel, using terrestrial cosmogenic nuclides, a denudation rate of 0.02-0.04 mm/a was measured on the summit of the footwall block. This denudation is in keeping with the drainage incision, suggesting a non-steady state for the fault footwall topography and a dominance of relief growth. Last, the analysis of the modern Raiale River longitudinal profile denoted an ungraded status, with two main knickzones that we interpret as transient forms due to tectonic perturbations, likely triggered by activity of the Paganica Fault during the end Early Pleistocene and the Late Pleistocene. Considering the 2009 L'Aquila earthquake coseismic rupture, we observe that the younger transience on the Raiale River longitudinal profile, if it is of tectonic origin, could have only been produced by much larger seismic events (i.e., Mw > 6.5) than those documented in the area by paleoseismological investigations. The collective results confirmed that in the Central Apennines, conditions of dynamic equilibrium are often not met, and that the persistence of transient perturbations induced by tectonics should be accounted for.

International audience

The evolution of continental relief results from the combined action of tectonic and climatic forcings. These processes do not act continuously but often through punctual events (earthquakes, major floods, landslides) whose integrated action over time (100 Kyr to Myr) leads to the formation of landscapes. The distribution of these extreme events is often described by statistical functions involving power-law relationships between frequency and magnitude, which, coupled with the non-linearity of the geomorphological response and threshold effects for the activation of erosion agents, leads to a complex and often poorly understood relief dynamics.Studying the influence of discharge variability helps to better constrain river incision and long-term relief evolution. The south-eastern margin of the Massif Central (France) is a very interesting target for such investigations because it presents episodes of very intense precipitation focused on the relief resulting in marked differences in the statistical discharges distributions across the landscape. Some theoretical river incision models incorporate such variability (Lague et al., 2005) but they have been confronted with real data only in a limited number of cases (DiBiase et al., 2011; Scherler et al., 2017; Campfort et al., 2020). Here we test these models in the Massif Central area and in particular on Cévennes, Ardèche and Margeride mountains by quantifying denudation rates using cosmogenic nuclides (10Be), characterizing discharges variability and performing morphological analysis on longitudinal rivers profiles.The analysis of 326 river gauging stations allow us to observe a strong gradient in discharge variability from the external SE border to the interior of the Massif Central. The 10Be concentrations measured from river sediments in 36 catchments imply a large variation of denudation rates between 29 mm/kyr and 126 mm/kyr. We compare these denudation rates with the spatial distribution of mean annual precipitations, local relief, slope and concavity index, and also integrate all the observations in the frame of a stochastic threshold incision model. Our results confirm the complex model predictions of non-linear relationships between mean denudation rates and the channel steepness index and their dependence on hydrological variability and run-off.key-words : extreme events, stochastic threshold incision model, denudation rates, discharge variability, morphometric parameters, Massif Central

International audience; Drawing upon a socio-constructivist perspective, this paper aims to gain insight into how two communities in the Italian Apennines region - differentially exposed to severe earthquakes in the past - remember, understand and plan for seismic phenomena. Avezzano was completely devastated in 1915, while the last significant event in Sulmona dates to 1706. However, both communities have indirectly experienced recent serious seismic events (e.g., L'Aquila earthquake in 2009 and Amatrice earthquake in 2016) as well as directly experienced lesser local tremblors. Interviews with citizens (N = 37) and stakeholders (N = 18) were conducted in the two cities and content-analysed with the support of NVivo software. The results show substantial differences in how respondents understand seismic events, access this information and prepare preventive strategies depending on their place of residence and role. The Avezzano community shares a more detached view, while the Sulmona community gives a more concerned picture. Moreover, the stakeholders tend to present an optimistic scenario, while citizens express a more critical viewpoint. Overall, the interview contents may be organised around two main oppositions: fatalism vs. empowerment in the face of an earthquake threat; and the will to forget about this risk vs. the need to remember it. The positioning on these two oppositions is defined by psychological, social and structural characteristics of individuals, and give rise to different representations of seismic risk and management. Such representations have practical implications for how the issue is addressed and faced in the communities' everyday life.

River terraces are geomorphological markers recording deformation. Here, we use four strath and fill river terraces along the Kizilirmak River in Turkey to unravel the deformation along the convex arc formed by the central North Anatolian Fault (NAF), a continental transform fault. 10Be, 26Al, 36Cl cosmogenic exposure ages of T3 and T2 strath terraces constrain their formation at 83 ± 15 ka and 67 ± 7 ka, respectively. We evidence frost-cracking during humid cold periods that bought younger carbonate cobbles on both terraces. T1, a younger fill terrace was probably emplaced during the MIS3 (30–40 ka) aggradational period or during the last glacial–interglacial transition. T0, the most recent fill terrace, was incised shortly before the 1668 earthquake based on 14C dating. It records a cumulated 14 ± 2 m offset linked to the 1943 and 1668 earthquakes. T3 shows a maximum offset of ~ 845 m and constrains a 10 mm/year geological slip rate that is lower than Holocene slip rates. It suggests temporal change in slip rates along the NAF. T2 and T3 also evidenced an uplift of 1 mm/year induced by transpressive deformation accommodated close to the NAF. Compared to the 0.28 mm/year obtained to the north, a larger portion of the shortening in the Central Pontides is accommodated close to the driving plate boundary. We also evidenced high cosmogenic-based erosion rates in Pontides during the Holocene, and even higher rates during T3 planation. Erosion rates were combined with present-day relief to infer a first-order minimal shortening of 12–16 km using simple mass balance principles in the Central Pontides. This long-term shortening is larger than the one induced by the Anatolian rotation suggesting a far field effect of the collision.

International audience; The aim of the Fault2SHA European Seismological Commission Working Group Central Apennines laboratory is to enhance the use of geological data in fault-based seismic hazard and risk assessment and to promote synergies between data providers (earthquake geologists), end-users and decision-makers. Here we use the Fault2SHA Central Apennines Database where geologic data are provided in the form of characterized fault traces, grouped into faults and master faults, with individual slip rate estimates. The proposed methodology first derives slip rate profiles for each master fault. Master faults are then divided into distinct sections of length comparable to the seismogenic depth to allow consideration of variable slip rates along master faults and the exploration of multi-fault ruptures in the computations. The methodology further allows exploration of epistemic uncertainties documented in the database (e.g. master fault definition, slip rates) as well as additional parameters required to characterize the seismogenic potential of fault sources (e.g. 3D fault geometries). To illustrate the power of the methodology, in this paper we consider only one branch of the uncertainties affecting each step of the computation procedure. The resulting hazard and typological risk maps allow both data providers and end-users (1) to visualize the faults that threaten specific localities the most, (2) to appreciate the density of observations used for the computation of slip rate profiles, and (3) interrogate the degree of confidence on the fault parameters documented in the database (activity and location certainty). Finally, closing the loop, the methodology highlights priorities for future geological investigations in terms of where improvements in the density of data within the database would lead to the greatest decreases in epistemic uncertainties in the hazard and risk calculations. Key to this new generation of fault-based seismic hazard and risk methodology are the user-friendly open source codes provided with this publication, documenting, step-by-step, the link between the geological database and the relative contribution of each section to seismic hazard and risk at specific localities.

The interaction between sedimentation/erosion and faulting represents one of the most intriguing topics in landscape and tectonics evolution. Only few studies have been able to document the feedback between faulting and sedimentary loading from field observations. Here, we focus on how sediment loading/unloading influences the dynamics of fault systems in the Fucino basin, in the Central Apennines (Italy). The Fucino basin represents a remarkable case study with respect to the other main extensional basins in the Apennines because of its large dimension, square shape, significant sediment thickness, and its endorheic nature throughout its evolution. We present a detailed structural and geomorphologic analysis of the Fucino basin and its surroundings, investigating the kinematic and geometry of each main fault strand. The slickenlines analysis reveals multiple families of slip-vectors and timing of activity, suggesting a change in extension slip-direction from N240° to N200° during middle Pleistocene. Using a local isostatic model, we estimate that up to the 30% of the vertical geological displacement of the faults, which overall ranges from 0.5 to 2.5km, is related to the sediment loading/unloading. We demonstrate a positive feedback between sedimentation and faulting which may also lead to a reorganization in fault kinematics related to a significant increase in vertical stress. We propose a conceptual model for the permanent endorheic configuration of the Fucino basin, which includes the effect of sediment loading.

International audience; The Mw 6.5 Norcia earthquake occurred on 30 October 2016, along the Mt Vettore fault (Central Apennines, Italy), it was the largest earthquake of the 2016-2017 seismic sequence that started 2 months earlier with the Mw 6.0 Amatrice earthquake (24 August). To detect potential slow slip during the sequence, we produced Interferometric Synthetic Aperture Radar (InSAR) time series using 12- to 6-day repeat cycles of Sentinel-1A/1B images. Time series indicates that centimeter-scale surface displacements took place during the 10 weeks following the Norcia earthquake. Two areas of subsidence are detected: one in the Castelluccio basin (hanging wall of the Mt Vettore fault) and one in the southern extent of the Norcia earthquake surface rupture, near an inherited thrust. Poroelastic and viscoelastic models are unable to explain these displacements. In the Castelluccio basin, the displacement reaches 13.2 +/- 1.4 mm in the ascending line of sight on 6 January 2017. South of the Norcia earthquake surface rupture (a zone between the Norcia and Amatrice earthquakes), the postseismic surface displacements affect a smaller area but reach 35.5 +/- 1.7 mm in ascending line of sight by January 2017 and follow a logarithmic temporal decay consistent with postseismic afterslip. Our analysis suggests that the structurally complex area located south of the Norcia rupture (30 October) is characterized by a conditionally stable frictional regime. This geometrical and frictional barrier likely halted rupture propagation during the Amatrice (24 August) and Norcia (30 October) earthquakes at shallow depth (

Item S1 (additional information on the modeling) and Item S2, (additional information on the sampling, analysis, and obtained dataset).

International audience; In 2016, the Mt. Vettore-Mt. Bove normal fault system (VBFS) broke during three earthquakes (Mw 6.0, Mw 5.9, and Mw 6.5), associated with clear coseismic ruptures. Based on high-resolution topography and geological field data, we determined the displacements of the VBFS. The distributions of the coseismic and postglacial displacements exhibit similar asymmetric shapes, suggesting self-similar slip profiles over the last 18 kyr. The highest displacement during the 2016 events is localized on the southern Mt. Vettore segments, the southern tip of the VBFS, which also showed the maximum throw of 32 m over the last 18 kyr yielding to a very fast throw rate of 1.6 ± 0.5 mm/yr. Assuming a constant throw rate, the geological displacement we determined suggests an inception age of 200–250 kyr for the surface rupturing faults that ruptured in 2016 on the Mt. Vettore sector. This value can be interpreted as the minimum age for the onset of those faults in the Mt. Vettore and might result from a southward shift of VBFS activity with a change of the fault system pattern. We infer that the observed slip distribution, maximum at Mt. Vettore and tapering-off southward, might be due to the VBFS lengthening processes towards the Laga Fault and its interaction with pre-existing structure such as Olevano-Antrodoco-Sibillini thrust that might play a key role in controlling the VBFS's evolution.

A driving motivator in many active tectonics studies is to learn more about the recurrence large and potentially destructive earthquakes, providing the means to assess the respective fault’s future seismic behavior. Doing so requires long records of earthquake recurrence. The lack of sufficiently long instrumental seismic records (that would be best suited for this task) has led to the development of other approaches that may constrain the recurrence of surface rupturing earthquakes along individual faults. These approaches take different forms, depending on the specific tectonic and geographic conditions of an investigated region.For example, around the Mediterranean Sea, we frequently find bedrock scarps along normal faults. Assuming that bedrock (i.e., fault free-face) exposure is caused by the occurrence of sub-sequent large earthquakes, we may measure certain rock properties to constrain the time and size of past earthquakes as well as the fault’s geologic slip-rate. A now-classic example in this regard is the measurement of 36Cl concentrations along exposed fault scarps in limestones.For the presented study, we looked at another property of the exposed fault free-face, namely its morphologic roughness. We aim to identify whether fault free-face roughness contains information to constrain earthquake occurrence and fault slip-rates following the assumption that sub-sequent exposure to the elements and sub-areal erosional conditions may leave a signal in how rough (or smooth) the fault free-face is (assuming a somewhat uniform pre-exposure roughness). Here, we present observations of fault free-face surface roughness for the Mt. Vettore fault (last ruptured in 2016) and the Rocca Preturo fault (The underlying models of fault free-face morphology were generated using the Structure-from-Motion approach and a large suite of unregistered optical images.). Employing different metrics to quantify morphologic roughness, we were indeed able to observe a) an increase in surface roughness with fault scarp height (i.e., longer exposure to sub-areal erosion causes higher roughness), and b) distinct (rather than gradual) changes in surface roughness, suggesting a correlation to individual exposure events such as earthquakes. Hence, fault free-face morphology of bedrock faults may serve as an additional metric to reconstruct earthquake recurrence patterns.

Correction for ‘Mass-shift mode to quantify low level 129I in environmental samples by ICP-MS/MS’ by Coralie Carrier et al., J. Anal. At. Spectrom., 2022, 37, 1309–1317, https://doi.org/10.1039/D2JA00128D.

International audience; The dynamics of carbonate-dominated landscapes is still debated, and first-order questions pertaining to the respective importance of chemical and mechanical weathering processes or the influence of climatic variability on denudation rates are largely open. To address these issues, we investigate the denudation pattern across a climatic gradient in Provence, SE France. We focused on a series of major carbonate mountain ranges with elevation spanning 200 to 2000 m and associated with >2-fold variations in mean annual temperature and precipitation. We collected 25 samples from 10 different mountain ranges and quantified denudation rates through the measurement of their Cl-36 concentrations in order to explore tectonic and climatic controls on these carbonate landscapes evolution. We observe that most of our samples experience denudation rates in the 30-60 mm/ka range (averaged over 5 to 40 ka), with no evident dependence on variations of mean annual temperature or precipitation. One range (Lure mountain) stands out as a significant outlier, with much higher denudation rates (>100 mm/ka) than adjacent sites (Ventoux mountain) at the same elevation and experiencing similar present-day environmental conditions. We explore in details the climatic, tectonic and geomorphological contexts of these two ranges in order to understand the reasons for this apparent 3-fold difference in denudation rates. A regionally-documented major Holocene hillslope destabilization event appears to be a likely candidate to explain the observed lower Cl-36 concentrations at the top of the Lure mountain. At longer wavelengths, our regional dataset shows no clear control of modem precipitation gradients on denudation rates, consistent with previous observations in landscapes underlain by other lithologies.

International audience; Key-points Folded alluvial surfaces and balanced cross-section constrain post-LGM and Neogene shortening-rates Decrease in shortening-rate and change in compression direction are inferred at 1-2 Ma Kinematic reorganization is best explained by a shift from Nubia-driven to Adria-driven convergence Abstract The eastern Southern Alps are located at the northern tip of the Adria microplate, which imposes 2.0-2.5-mm/yr of N-S-convergence relative to stable Eurasia. We map surface evidence of recent folding/faulting in this area from a 5-m-DEM. In the eastern part of the belt, observations reveal a 30-km-wide zone of active folding composed of at least five growing anticlines. The most recent ones warped the post-glacial alluvial surface by

International audience; In this study, we present a new glacial chronology based on 20 in situ-produced 36Cl-based cosmic ray exposure datings from moraine boulders and bedrock from the Throne of Zeus (TZ) and Megala Kazania (MK) cirques on Mount Olympus. The 36Cl derived ages of glacial landforms range from 15.6 ± 2.0 to 0.64 ± 0.08 ka, spanning the Late-glacial and the Holocene. The Late-glacial, recorded in both cirques, is partitioned in three distinct phases (LG1-3): an initial phase of moraine stabilization at 15.5 ± 2.0 ka with subsequent deglaciation starting at ∼14 ka (LG1), followed by a shift to marginal conditions for glaciation at 13.5 ± 2.0 ka (LG2), sustained by large amounts of wind-blown snow, despite regional warming. Glacial conditions returned at 12.5 ± 1.5 ka (LG3) and were characterized by low air temperatures and glacier shrinking. The Holocene glacial phases (HOL1-3) are recorded only in the MK cirque, likely due to its topographic attributes. An early Holocene glacier stillstand (HOL1) at 9.6 ± 1.1 ka follows the regional temperatures recovery. No glacier activity is observed during the mid-Holocene. The Late Holocene glacier expansions, include a moraine stabilization phase (HOL2) at 2.5 ± 0.3 ka, during wet conditions and solar insolation minima, while (HOL3) corresponds to the early part of the Little Ice Age (0.64 ± 0.08ka). Our glacial chronology is coherent with glacial chronologies from several cirques along the northeast Mediterranean mountains and in pace with numerous proxies from terrestrial and marine systems from the north Aegean Sea.

International audience; Landscape evolution from the Early 1st millennium BCE to the mid-1st millennium CE is poorly documented around major archaeological sites in Crete. In a previous publication, the general landscape configuration in the vicinity of ancient Phaistos was reconstructed using a palaeoenvironmental approach, from the Proto-Palatial period (ca. 2000 BCE) to the Late-Proto Geometric period (ca. 8th cent. BCE). However, the physiography of the landscape, its hydrology and vegetation history remained uncertain for the later archaeological periods. In the present study, additional radiocarbon dates (8) together with pollen, mollusc and sedimentological analyses (CM diagram) were conducted on previously documented sediment cores. These new results enable us to reconstruct in greater detail the landscape history from the Early Archaic period to Late Byzantine times. The results indicate the continuous presence of swampland from the Proto-Geometric period (10th cent. BCE) probably until the initial stages of the Classical period (5th cent. BCE). Subsequently, during the Classical and Hellenistic periods, there was a short interval of alluvial input of terriginous sediments (not exceeding two centuries in duration) which is directly linked with the complete drying up and drainage of the swampland. We address the issue of the possible climatic origin of this abrupt hydrological change, especially in relation to regional climate change and the sedimentary history of adjacent rivers and streams. Tectonic activity in the area is also an important factor and can be invoked as a potential environmental influence. Anthropogenic factors are also considered, even though there is no direct archaeological evidence of drainage in the western Messara Plain during the Archaic and Classical periods. Finally, from Roman times to the Early Byzantine period, floodplain development prevailed in the area and ponds formed locally, in particular from the Late Hellenistic to Early Byzantine periods; this was related to the climatic conditions of the Roman Warm period. Pollen analysis reveals an open forested landscape during the time interval under investigation, within which domesticated plants such as Olea (olive) were present. However, the representation of Olea decreases continuously from the Late Geometric period to Byzantine times, probably indicating much lower intensity of land use than during Minoan times and possibly also related to the generally colder climatic conditions in Crete from the 8th cent. BCE until the 1st Cent. CE. During this latter interval, there is also the first pollen analytical evidence of Vitis sp.

Located at the northeastern corner of the Adria microplate, the Alps-Dinarides junction represents a key region for understanding how the Adria microplate interacts with stable Europe. However, little is known on how the present-day deformation imposed by the rotation of the Adria microplate is absorbed across the Dinarides. Using morphotectonic analysis based on satellite and aerial images, accurate topographical maps, and digital elevation models combined with field investigations, we mapped in detail the three main active faults of the Northern Dinarides. Geomorphic and geological cumulative displacements ranging from a few meters to several kilometers have been identified on those faults and dated for the most recent ones using 36 Cl exposure dating. Those results yielded a total right-lateral motion of 3.8 ± 0.7 mm/yr oriented N317. Comparing our results with the motion expected from Adria rotation models suggests that the Northern Dinarides absorbs most of the predicted Adria-Eurasia motion, thus representing the eastern boundary of the microplate. However, a significant E-W component is lacking, suggesting that part of the stress imposed by the microplate rotation is transferred farther to the east. Finally, bounds placed on the Plio-Pleistocene kinematics confirm that faulting onset occurred during the Early Pliocene and evidence a significant kinematic change at the Early/Middle Pleistocene boundary.

Morphological and geological observations reveal that most Apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long. Although these faults have undergone numerous paleoseismological investigations, quantitative data remain crucially lacking for a large number of fault segments. Because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future, we investigated the Holocene seismic history of the Pizzalto normal fault, a 13 km long fault segment belonging to the Pizzalto-Rotella-Aremogna fault system in the Apennines. We collected 44 samples from the Pizzalto fault plane exhumed during the Holocene and analyzed the 36Cl and rare earth element (REE) contents. Together, the 36Cl and REE concentrations show that at least six events have exhumed 4.4 m of the fault scarp between 3 and 1 ka, with slip per event values ranging from 0.3 to 1.2 m. No major events have been detected over the last 1 kyr. The Rotella-Aremogna-Pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1.2 kyr and a low to moderate probability (ranging from 4% to 26%) of earthquake occurrence over the next 50 years.

The Doruneh Fault System (DFS) is one of the major active strike-slip faults in the Arabia-Eurasia collision zone. Despite its geological activity, no large (M ≥ 6.5) historical or instrumental earthquakes have been recorded along it. To date, the rate and distribution of slip, as well as the seismic behavior of the DFS, have been unknown. We reconstructed 67 geomorphic offsets recorded by three successive alluvial abandonment surfaces (Q1, Q2, and Q3) displaced along the western (WFZ) and central (CFZ) fault zones. The determined ages of ~12, ~36, and ~120 ka, using in situ-produced 10 Be and 36 Cl cosmogenic nuclides for theses surfaces, allowed to estimate three sets of individual left-lateral slip rates and consequently to describe the spatiotemporal distribution of slip along the CFZ and WFZ. The slip rates averaged over time intervals of ~36 and ~120 ka reveal variable slip rates along length but similar slip rates at a point with a maximum rate of ~8.2 mm/yr. During the Holocene, however, the fault slip behavior appears more complex, with a maximum rate of ~5.3 mm/yr. The CFZ is divided into two ~4 km apart segments, with symmetrical slip distributions relative to a persistent boundary, which has not been ruptured over the last ~12 ka. The maximum length of seismic fault segments varies from 70 to 100 km, which could produce earthquakes with a magnitude of M w 7.2–7.4. This emphasizes the necessity of segmentation models for long strike-slip faults that may not necessarily rupture along their whole length during a single earthquake.

This study investigates the possibility of Holocene glaciation on Mount Olympus (Greece) with a respective local temperature–precipitation equilibrium line altitude (TP-ELA) at c. 2200 m a.s.l., based on geomorphologic and paleoclimatic evidence. At present, the local TP-ELA is situated above the mountain’s summit ( c. 2918 m a.s.l.), but permanent snowfields and ice bodies survive within Megala Kazania cirque between c. 2400 and c. 2300 m a.s.l., because of the cirque’s maritime setting that results from its close proximity ( c. 18 km) to the Aegean Sea and of the local topographical controls. The snow and ice bodies occupied a considerably larger area and attained a stabilization phase between AD 1960 and 1980, also manifested from aerial photographs, a period characterized by increased winter precipitation ( Pw) with subsequent TP-ELA depression to c. 2410 m a.s.l. Mid- to late-20th-century Pw and TP-ELA variations exhibit negative correlations with the winter North Atlantic Oscillation index (NAOw) at annual and multidecadal (30 years) timescales. Late Holocene (AD 1680–1860) reconstructed summer mean temperatures were lower by Ts w phases, thus bracketing this time interval as a favorable one to glacial formation and/or advance. Millennial-scale annual precipitation reconstructions at the hypothesized TP-ELA ( c. 2200 m a.s.l.) point the period between 8 and 4 kyr BP as another glacier-friendly candidate. The mid-Holocene rather simplistic sequence of potential glacial advance phase was disturbed by short-lived cold climatic deteriorations, well-documented over the northern Aegean region that may partly explain the multicrested shape of the highest ( c. 2200 m a.s.l.) morainic complex of Megala Kazania cirque.

International audience; Central Italy is characterized by a network of active faults that interact in a complex manner. Coseismic Coulomb stress changes have been invoked by several authors to explain the concentration of moderate-to-strong earthquakes in this region, but none has considered the time-dependent viscoelastic relaxation of the lower crust and upper mantle as a possible additional source of stress changes at a regional scale. Here starting from the 1915 M w 6.9 ± 0.2 Fucino earthquake, we calculated the coseismic plus postseismic Coulomb failure stress changes (ΔCFS) due to eight moderate-to-strong earthquakes that have struck Central Italy in the last century and culminated with the 2016-2017 sequence. Results from this modeling coupled with some synthetic tests simulating normal fault earthquakes with different magnitudes allowed us to highlight the importance of postseismic processes. In particular, the viscoelastic stress transfer due to events of M w ≥ 6.5 can modify the spatial distribution of ΔCFS on a centennial timescale and therefore trigger events at larger distances. In addition, using these results, we identified other earthquake clusters in the historical catalogue (last 618 years), which, like the 1915-2017 series, were potentially modulated by both coseismic and postseismic processes. Finally, considering our calculations combined with historical and paleoseismological data, we suggest that several faults in Central Italy may be at present close to failure.

International audience; After 24 August and 30 October 2016 central Italy earthquakes (Mw 6.0 and 6.5, respectively), photogrammetry and geodetic survey were performed at various sites along a 6‐km‐long portion of the rupturing Monte Vettore fault system, providing very high‐resolution georeferenced 3‐D point clouds and imagery of the 24 August rupture and a data set of bedrock fault scarp before/after the 30 October earthquake. The maximum coseismic displacement for both events occurs near Scoglio dell' Aquila with an average normal dip slip of 22 ± 4 and 184 ± 6 cm, respectively. Coseismic slip vectors and meter‐scale corrugation axis are oriented N280 ± 10° on the ~N140° striking main Vettore fault involving oblique normal slip with a right‐lateral component and N205 ± 10° on ~N170° fault strands implying oblique normal slip with a left‐lateral component. We quantify the near‐field coseismic displacements of the Monte Vettore fault for the 30 October event: the footwall has been translated horizontally by 42 ± 2 cm toward the ENE and uplifted by 11 ± 2 cm. The hangingwall has moved horizontally by 26 ± 2 cm, toward the NW, in a direction parallel to the fault plane and subsided by 116 ± 2 cm. The fault geometry and our determined surface coseismic slip vectors are mechanically compatible with a σ3 = N65 ± 15°. This stress regime is consistent with the 30 October 2016 focal mechanism and the relative motion between the Adriatic microplate and the Tyrrhenian coastal region. The 30 October surface rupture results from seismic slip at depth and thus has a tectonic origin.

Denudation of carbonate terrains dominated by chemical weathering can be treated as a rain gauge proxy, because the mass lost by dissolution over time is proportional to the time-integrated precipitation. Therefore, the denudation history of carbonate landscapes may provide paleoprecipitation data and shed light on the interactions between climate, denudation, and tectonic uplift. We apply this approach to constrain 10 4 –10 7 yr average precipitation along the western Dead Sea Rift (DSR) margin, which is underlain predominantly by carbonate rocks and maintains a climatic gradient from Mediterranean to hyperarid along its axis and between its windward and leeward flanks. The comparison between total denudation (from a Turonian datum), denudation rate calculations (from in-situ 36 Cl measurements), and present-day mean annual precipitation shows that (1) total denudation correlates with denudation rates and both correlate with precipitation, and (2) over the lifetime of the range (10–20 m.y.), the effective precipitation gradient across the range was higher than at present by at least 40% on average. Along the ∼450-km-long range, the denudation gradient is probably compensated by isostatic uplift. We suggest that along the western DSR margin, and possibly in other carbonate terrains, precipitation (to a threshold precipitation of ∼1000 mm yr –1 ) controls the long-term denudation rate and the subsequent compensating uplift.

International audience; The influence of the morphological setting on the denudation of carbonate landscapes and the respective contributions of mechanical and chemical weathering processes are still debated. We have addressed these questions by measuring 36Cl concentrations in 40 samples from the Luberon mountain, SE France, to constrain the denudation of various landscape elements. We observe a clear contrast between the local denudation rates from the flat summit surface, clustered around 30 mm/ka, and the basin‐average denudation rates across the flanks, ranging from 100 to 200 mm/ka. This difference highlights the transient evolution of the range, whose topography is still adjusting to previous uplift events. Such a pattern also suggests that carbonate dissolution is not the only driver of denudation in this setting, which appears to be significantly controlled by slope‐dependent processes.

We perform aftershock probabilistic seismic hazard analysis (APSHA) of the ongoing aftershock sequence following the Amatrice August 24th, 2016 Central Italy earthquake. APSHA is a time-dependent PSHA calculation where earthquake occurrence rates decrease after the occurrence of a mainshock following an Omori-type decay. In this paper we propose a fault source model based on preliminary evidence of the complex fault geometry associated with the mainshock. We then explore the possibility that the aftershock seismicity is distributed either uniformly or non-uniformly across the fault source. The hazard results are then computed for short-intermediate exposure periods (1-3 months, 1 year). They are compared to the background hazard and intended to be useful for post-earthquake safety evaluation.

We recover the Holocene earthquake history of seven seismogenic normal faults in the Fucino system, central Italy. We collected 800 samples from the well-preserved limestone scarps of the faults and modeled their 36Cl concentrations to derive their seismic exhumation history. We found that > 30 large earthquakes broke the faults in synchrony over the last 12 ka. The seven faults released strain at the same periods of time, 12-9 ka, 5-3 ka, and 1.5-1 ka. On all faults, the strain accumulation and release occurred in 3-6 ka supercycles, each included a 3-5 ka phase of slow (≤ 0.5-2 mm/yr) strain accumulation in relative quiescence, followed by a cluster of three to four large earthquakes or earthquake sequences that released most of the strain in

Modelling the evolution of the concentration of in-situ produced cosmogenic nuclides as a function of depth (depth-profile) has been developed to allow determining both the exposure duration and the denudation rate affecting geomorphic features. However, material sampled through surficial deposits may exhibit an inherited component resulting from exposure to cosmic rays before deposition. In case of homogeneous inheritance, this inherited component may be estimated through sampling at increasing depths and subsequently subtracted. In case of variable inheritance, the measured concentrations are scattered and the random distribution of the depth-profile concentrations prevents modelling confidently a depth-profile and precludes constraining an exposure duration. Often observed in desert and endorheic regions, this greatly restricts the possibilities to determine an accurate abandonment age of alluvial surfaces in such environments. Provided the denudation is demonstrated negligible, a method for determining a more accurate range of minimum inheritance, hence a more accurate maximum abandonment age for a given alluvial surface, is proposed. This method, based on the rejuvenation of depth-profile samples, relies on the simple hypothesis that at least one of the depth-profile samples would be emplaced with no or negligible inherited component and on the obvious principle that none of analysed sample has been emplaced with a negative cosmogenic nuclide concentration. The method consists then in determining which of the measured depth-profile sample may have been emplaced with a null CRE concentration; i.e., with a zero inheritance value. This requires to calculate the in-situ duration of exposure needed to reach the concentration measured for each depth-profile sample and to retain the one that provides the smallest in-situ exposure duration. Several examples from alluvial surfaces of central Iran illustrate the profile rejuvenation method and highlight a variable inheritance ranging between 1.5 × 10 5 and 16.1 × 10 5 at/g (SiO 2 ) for terraces whose abandonment ages range from ten to several hundreds of ka.

Since its discovery, the Chauvet cave elaborate artwork called into question our understanding of Palaeolithic art evolution and challenged traditional chronological benchmarks [Valladas H et al. (2001) Nature 413:419–479]. Chronological approaches revealing human presences in the cavity during the Aurignacian and the Gravettian are indeed still debated on the basis of stylistic criteria [Pettitt P (2008) J Hum Evol 55:908–917]. The presented 36 Cl Cosmic Ray Exposure ages demonstrate that the cliff overhanging the Chauvet cave has collapsed several times since 29 ka until the sealing of the cavity entrance prohibited access to the cave at least 21 ka ago. Remarkably agreeing with the radiocarbon dates of the human and animal occupancy, this study confirms that the Chauvet cave paintings are the oldest and the most elaborate ever discovered, challenging our current knowledge of human cognitive evolution.

The chauvet cave discovery in 1994 has challenged our archeological, art and chronological benchmarks previously admitted and based on the chronological stylistic framework. The aim of this study is dating of the major rockfalls, which have closed the Chauvet cave to the human and animals. This work shows the results of the geomorphological approach combining high-resolution topographic survey (terrestrial LiDAR) and cosmogenic dating. The rockfall scars and rockfall deposit 3D analysis has permitted to reconstruct the Chauvet cave paleo entrance. The rock sampling strategy is based on the existence of three rockfall scars on the rockwall overhanging the Chauvet cave. All the 36Cl production factor was considered and both of them are derived from the 3D topographic. These results allow establishing a coherent and absolute chronological framework of the Chauvet cave entrance for 34,000 years until its definitively and sudden closure there 22, 000 years., La découverte de la grotte Chauvet-Pont-d Arc, en 1994, et surtout l'âge des représentations préhistoriques, ont bouleversé les schémas jusque-là admis sur l'art pariétal. Ce travail de recherche géomorphologique, qui s 'insère dans le cadre des études scientifiques pluridisciplinaires menées sur cette cavité, porte sur le processus et la datation de la fermeture qui a rendu inaccessible cette grotte aux Hommes et aux animaux de la Préhistoire, suite à l'accumulation d'un dépôt d'écroulement dans le paléoporche de la grotte. L'analyse 3D de la niche d'arrachement et de la masse écroulée a été complétée par une étude chronologique via l'utilisation de l'isotope cosmogénique du 36Cl. Le détachement du pan de paroi à l'origine de la fermeture de la grotte préhistorique a mis au jour une nouvelle surface auparavant non exposée aux rayonnements cosmiques. La stratégie d'échantillonnage a été guidée par l'identification de plusieurs niches d'arrachement révélées sur la paroi par des mesures topographiques au LiDAR terrestre. Enfin, les facteurs de production ont été contraints à partir des connaissances géométriques et géomorphologiques du site. Ces résultats permettent d'établir un cadre cohérent et absolu de l'évolution de l'entrée de la grotte Chauvet depuis 34 000 ans jusqu'à sa fermeture brutale et définitive il y 22 000 ans., Sadier Benjamin, Benedetti Lucilla, Delannoy Jean-Jacques, Bourlès Didier, Jaillet Stéphane, Arnaud Judicaël, Jarry Benoit, Vermorel Guillaume, Geneste Jean-Michel. Datations 36Cl de la fermeture de la grotte Chauvet, implications géomorphologiques et archéologiques. In: Collection EDYTEM. Cahiers de géographie, numéro 13, 2012. Karsts, Paysages et Préhistoire. pp. 63-78.

SUMMARY Be and 36 Cl cosmic ray exposure (CRE) and optically stimulated luminescence (OSL) dating of offset terraces have been performed to constrain the long-term slip rate of the Dehshir fault. Analysis of cosmogenic 10 Be and 36 Cl in 73 surface cobbles and 27 near-surface amalgamscollectedfrominsetterracesdemonstratestheoccurrenceofalowdenudationrateof 1mM a −1 and of a significant and variable inheritance from exposure prior to the aggradation of these alluvial terraces. The significant concentrations of cosmogenic nuclides measured in the cobbles collected within the riverbeds correspond to 72 ± 20 ka of inheritance. The mean CREageofthesurfacesamplescollectedontheolderterraceT3is469 ±88kabuttheanalysis of the distribution of 10 Be concentration in the near-surface samples discard ages older than 412 ka. The mean CRE age of the surface samples collected on terrace T2 is 175 ± 62 ka but the 10 Be depth profile discard ages older than 107 ka. For each terrace, there is a statistical outlier with a younger age of 49.9 ± 3.3 and 235.5 ± 35.4 ka on T2 and T3, respectively. The late sediments aggraded before the abandonment of T2 and inset levels, T1 b and T1a, yielded OSL ages of, respectively, 26.9 ± 1.3, 21.9 ± 1.5 and 10.0 ± 0.6 ka. For a given terrace, the OSL ages, where available, provide ages that are systematically younger than the CRE ages. These discrepancies between the CRE and OSL ages exemplify the variability of the inheritance and indicate the youngest cobble on a terrace, that minimizes the inheritance, is the most appropriate CRE age for approaching that of terrace abandonment. However, the upper bound on the age of abandonment of a terrace that is young with respect to the amount of inheritance is best estimated by the OSL dating of the terrace material. For such terraces, the CRE measurements are complementary of OSL dating and can be used to unravel the complex historyofweatheringandtransportinthecatchmentofdesertalluvialfans.Thiscomprehensive set of dating is combined with morphological offsets ranging from 12 ± 2t o 380± 20 m to demonstrate the Dehshir fault slips at a rate in the range 0.9 mm yr −1 –1.5 mm yr −1 .T he variable inheritance exemplified here may have significant implications for CRE dating in arid endorheic plateaus such as Tibet and Altiplano.

International audience; Although the geology and structure of the Zagros fold-and-thrust belt (Iran) have been studied extensively, the distribution of active deformation across the belt and its seismotectonic behaviour remain controversial. We have mapped deformed fluvial terraces along the Dalaki and Mand rivers in the central Zagros, as well as marine terraces along the Persian Gulf, in order to unravel the spatial pattern of vertical displacements and to analyse active deformation and its implications for seismicity. Using appropriate fold models based on structural data allows interpreting such vertical displacements in terms of horizontal shortening across the fold structures. Obtaining well-constrained rates of deformation depends on reliably dating deformed geomorphic markers; by combining different dating techniques and correlations to sea level history, we propose an internally consistent set of ages, which allow the first geomorphic estimates of shortening rates absorbed by individual structures in the central Zagros. Our results show that shortening on Late Pleistocene timescales is concentrated in the frontal part of the belt, consistent with recent GPS data. Three or four frontal structures appear to absorb practically all of the active shortening across the Zagros, broadly consistent with a normal forward-propagating deformation sequence but with local out-of-sequence activation of structures behind the forward-most folds. The localization, rate and direction of surface shortening across individual structures appear decoupled from basement deformation, as indicated by structural cross-sections and the distribution of seismicity. Such independent behaviour suggests that the sedimentary cover of the frontal Zagros is decoupled from the basement, most probably at the level of the Hormuz Salt. This weak basal detachment level, together with several intermediate décollement levels, appears to be responsible for the overwhelmingly aseismic deformation of the Zagros sedimentary cover, and also to control the development of a large panel of fold structures, from detachment to fault-propagation folds with varying wavelength and rooting depth.

International audience; The cosmonuclide Cl-36 is relevant for hydrological applications due to its conservative chloride form. Cl-36 measurements are commonly performed by Accelerator Mass Spectrometry (AMS) while stable chlorine concentration measurements are usually performed by ion chromatography (IC). They can also be achieved by Isotope Dilution-Accelerator Mass Spectrometry (ID-AMS) which offers the advantage of the simultaneous determination of both Cl and Cl-36 contents. The range of applicability of this method has been assessed on rock samples but, to our knowledge, no experimental tests were conducted on water samples characterized by low chloride contents. This study aims at investigating the accuracy and precision of the ID-AMS method for such low chlorine water samples for which chloride and Cl-36 determinations remain highly challenging. First, internal and external errors were evaluated on the measured ratios and uncertainties on Cl and Cl-36 concentrations were assessed at +/- 5% and +/- 7% respectively using standard error propagation calculations. Focused on the 0.1 to 10 mg center dot L-1 concentration range, the Cl concentrations of thirty-five gravimetric standards were determined by ID-AMS leading to a 1:1 line (R-2 = 0.99) and a 1-sigma uncertainty on [Cl-] of +/- 5%, consistently with the propagated uncertainty. Finally, the optimal sample volume to reach accurate Cl-36 and Cl measurements with ID-AMS for water sample concentrations within the 0.1 to 10 mg center dot L-1 range has been theoretically estimated. (C) 2015 Elsevier B.V. All rights reserved.

International audience; The late-Cenozoic kinematic and late-Pleistocene paleoearthquake history of the Spili Fault is examined using slip-vector measurements and in situ cosmogenic (Cl-36) dating, respectively. The Spili Fault appears to have undergone at least three successive but distinct phases of extension since Messinian (similar to 7 Ma), with the most recent faulting resulting in the exhumation of its carbonate plane for a fault-length of similar to 20 km. Earthquake-slip and age data show that the lower 9 m of the Spili Fault plane were exhumed during the last similar to 16,500 years through a minimum of five large-magnitude (Mw > 6) earthquakes. The timing between successive paleoearthquakes varied by more than one order of magnitude (from 800 to 9000 years), suggesting a highly variable earthquake recurrence interval during late Pleistocene (CV = 1). This variability resulted to significant fluctuations in the displacement rate of the Spili Fault, with the millennium rate (3.5 mm/yr) being about six times faster than its late-Pleistocene rate (0.6 mm/yr). The observed variability in the slip-size of the paleoearthquakes is, however, significantly smaller (CV = 0.3). These data collectively suggest that the Spili Fault is one of the fastest moving faults in the forearc of the Hellenic subduction margin. (C) 2014 Elsevier Ltd. All rights reserved.

We investigated two prominent, ~E-W trending scarps in Quaternary sediments, located close to the town of Vodice in the Ljubljana Basin (central Slovenia). By using detailed geomorphological analysis of the scarps, field surveying, and structural observations of deformed Quaternary sediments, we conclude that the scarps are the surface expression of a N-dipping thrust fault that has been active during the Quaternary. From Optically Stimulated Luminescence and Infrared Stimulated Luminescence dating of deformed Quaternary sediments we estimate a slip rate of 0.1 to 0.3 mm a-1 in the last 133 ka. Using the published empirical fault-scaling relationships, we estimate that an earthquake of magnitude 5.9 to 6.5 may be expected on the Vodice thrust fault. The fault may, therefore, present a major seismic hazard for the densely populated and urbanised region of central Slovenia.

Η παλαιοσεισμική δραστηριότητα στο ρήγμα του Σπηλίου μελετήθηκε χρησιμοποιώντας μία πρωτοποριακή μέθοδο που συνδιάζει μετρήσεις Σπανίων Γαιών (REE) και κοσμογενών ισοτόπων 36Cl πάνω στην σεισμικά αποκαλυμμένη επιφάνεια του ρήγματος. Η ανάλυση των δεδομένων δείχνει ότι το ρήγμα είναι ενεργό και έχει φιλοξενήσει τουλάχιστον 5 μεγάλου-μεγέθους σεισμούς τα τελευταία 16500 χρόνια. Οι δύο πιο πρόσφατοι σεισμοί έλαβαν χώρα κατά την περίοδο 100-900 ετών πρίν από σήμερα και άθροισαν συνολικά 3.5 μέτρα σεισμικής μετατόπισης. Η χρονολογία των παλαιότερων 3 σεισμών προσδιορίσθηκε στα 7300, 16300 και 16500 χρόνια πριν από σήμερα με σεισμικές ολισθήσεις 2.5, 1.2 και 1.8 μέτρα, αντίστοιχα. Από το μέγεθος των σεισμικών ολισθήσεων συμπεραίνουμε ότι το μέγεθος των σεισμών που προκλήθηκαν από το ρήγμα του Σπηλίου κυμάνθηκε από Μ 6.3-7.3 ενώ ο μέσος ρυθμός επανάληψης τους ήταν ~4200 χρόνια. Τα παραπάνω δεδομένα αποκαλύπτουν ότι το ρήγμα του Σπηλίου είναι ένα από τα πιο ενεργά ρήγματα στην Κρήτη και οι σεισμικές παράμετροί που σχετίζονται με την δραστηριότητά του πρέπει να συμπεριληφθούν στο μοντέλο σεισμικής επικινδυνότητας της Ελλάδας., The paleoearthquake activity on the Spili Fault is examined using a novel methodology that combines measurements of Rare Earth Elements (REE) and of in situ cosmogenic 36Cl on the exhumed fault scarp. Data show that the Spili Fault is active and has generated a minimum of five large-magnitude earthquakes over the last ~16500 years. The timing and, to a lesser degree, the slip-size of the identified paleoearthquakes was highly variable. Specifically, the two most recent events occurred between 100 and 900 years BP producing a cumulative displacement of 3.5 meters. The timing of the three older paleoearthquakes is constraint at 7300, 16300 and 16500 years BP with slip sizes of 2.5, 1.2 and 1.8 meters, respectively. The magnitude of the earthquakes that produced the measured co-seismic displacements, ranges from M 6.3-7.3 while the average earthquake recurrence interval on the Spili Fault is about 4200 years. The above data suggest that the Spili is among the most active faults on Crete and its earthquake parameters may be incorporated into the National Seismic Hazard Model.

Because the intensity and energy spectrum of the cosmic ray flux are affected by atmospheric depth and geomagnetic-field strength, cosmogenic nuclide production rates increase considerably with altitude and to a lesser degree with latitude. The scaling methods used to account for spatial variability in production rates assume that all cosmogenic nuclides have the same altitude dependence. In this study we evaluate whether the production rates of cosmogenic 36 Cl, 3 He and 21 Ne change differently with altitude, which is plausible due to the different threshold energies of their production reactions. If so, nuclide-specific scaling factors would be required. Concentrations of the three cosmogenic nuclides were determined in mafic phenocrysts over an altitude transect between 1000 and 4300 m at Kilimanjaro volcano (3°S). Altitude dependence of relative production rates was assessed in two ways: by determination of concentration ratios and by calculation of apparent exposure age ratios for all nuclide pairs. The latter accounts for characteristics of 36 Cl that the stable nuclides 3 He and 21 Ne do not possess (radioactive decay, high sensitivity to mineral composition and significant contributions from production reactions other than spallation). All ratios overlap within error over the entire transect, and altitudinal variation in relative production rates is not therefore evident. This suggests that nuclide-specific scaling factors are not required for the studied nuclides at this low-latitude location. However, because previous studies have documented anomalous altitude-dependent variations in 3 He production at mid-latitude sites, the effect of latitude on cross-calibrations should be further evaluated. We determined cosmogenic 21 Ne/ 3 He concentration ratios of 0.1864 ± 0.0085 in pyroxenes and 0.377 ± 0.018 in olivines, agreeing with those reported in previous studies. Despite the absence of independently determined ages for the studied lava surfaces, the consistency in the dataset should enable progress to be made in the determination of the production rates of all three nuclides as soon as the production rate of one of the nuclides has been accurately defined. To our knowledge this is the first time that 36 Cl has been measured in pyroxene. The Cl extraction method was validated by measuring 36 Cl in co-existing plagioclase phenocrysts in one of the samples.

Cosmic-ray exposure dating of preserved, seismically exhumed limestone normal fault scarps has been used to identify the last few major earthquakes on seismogenic faults and recover their ages and displacements through the modelling of the content of in situ [36Cl] cosmonuclide of the scarp rocks. However, previous studies neglected some parameters that contribute to 36Cl accumulation and the uncertainties on the inferred earthquake parameters were not discussed. To better constrain earthquake parameters and to explore the limits of this palaeoseismological method, we developed a Matlab® modelling code (provided in Supplementary information) that includes all the factors that may affect [36Cl] observed in seismically exhumed limestone fault scarp rocks. Through a series of synthetic profiles, we examine the effects of each factor on the resulting [36Cl], and quantify the uncertainties related to the variability of those factors. Those most affecting the concentrations are rock composition, site location, shielding resulting from the geometry of the fault scarp and associated colluvium, and scarp denudation. In addition, 36Cl production mechanisms and rates are still being refined, but the importance of these epistemic uncertainties is difficult to assess. We then examine how pre-exposure and exposure histories of fault-zone materials are expressed in [36Cl] profiles. We show that the 36Cl approach allows unambiguous discrimination of sporadic slip versus continuous creep on these faults. It allows identification of the large slip events that have contributed to the scarp exhumation, and provides their displacement with an uncertainty of +/- ~25 cm and their age with an uncertainty of +/-0.5-1.0 kyr. By contrast, the modelling cannot discriminate whether a slip event is a single event or is composed of multiple events made of temporally clustered smaller size events. As a result, the number of earthquakes identified is always a minimum, while the estimated displacements are maximum bounds and the ages the approximate times when a large earthquake or a cluster of smaller earthquakes have occurred. We applied our approach to a data set available on the Magnola normal fault, Central Italy, including new samples from the buried part of the scarp. Reprocessing of the data helps to refine the seismic history of the fault and quantify the uncertainties in the number of earthquakes, their ages and displacements. We find that the Magnola fault has ruptured during at least five large earthquakes or earthquake clusters in the last 7 ka, and may presently be in a phase of intense activity.

International audience; This study on the Cap Canaille cliff (N 43.19°, E 5.55°, Cassis, SE France) combines cosmic ray exposure (CRE) dating using two cosmogenic nuclides (in situ-produced 10Be and 36Cl) and morphological analyses to gain a better understanding of a major coastal cliff collapse event. Morphological analysis reveals evidence (cliff morphology, presence of big collapsed blocks) of a possible major collapse of Cap Canaille in the past. Aerial pictures and GIS software allow estimation of a potential collapsed volume of at least 7 × 106 m3, of which roughly 6 × 106 m3 fell into the Mediterranean Sea. In situ-produced 10Be and 36Cl concentrations were measured in samples collected on collapsed block surfaces and in situ-produced 10Be was measured along the cliff face to date the last major collapse event. Statistical analysis of the CRE ages calculated from cliff samples shows that these ages cluster around 3.5 and 6.7 ka, suggesting the existence of a two-step past major collapse. The older ages obtained (at 9 and 12 ka) coincides with the approach of present day sea level, implying a control of sea level on the cliff retreat. The CRE ages calculated from collapsed block samples are more scattered (toward younger ages) due to several geomorphological factors. The estimated collapsed volume associated with the last major collapse around 3.5 ka seems sufficient to have triggered a local tsunami in the Cassis Bay, if it fell at once into the sea.

International audience; The aim of this work is to constrain the Late Quaternary activity of two major dextral strike-slip faults of the Zagros fold-and-thrust belt of Southern Iran, within the framework of right-oblique convergence between Arabia and Eurasia. The NW-trending Main Recent fault marks the rear of the belt along two thirds of its length. Its southeastern tip connects to the northern termination of the N-trending Kazerun Fault, which affects the entire width of the belt. Horizontal slip rates have been estimated on these two faults over the last 140 ka from lateral offsets of streams and fans and in situ cosmogenic 36Cl exposure dating of cobbles sampled on the surface of these geomorphic features. Compared to GPS data, the obtained minimum slip rate of 3.5–12.5 mm yr−1 on the Main Recent Fault implies strike-slip partitioning of the convergence along this fault. Minimum slip rate of the Kazerun Fault is 2.5–4 mm yr−1 for its northern strand, 1.5–3.5 mm yr−1 for its central segment and is negligible for its southern segment. These results are consistent with southward distribution of the slip from along the Main Recent Fault to the longitudinal thrusts and folds of the fold-and-thrust belt through the Kazerun Fault, with a decrease of slip from the southeastern tip of the Main Recent Fault towards the southern termination of the Kazerun Fault. The Kazerun and associated faults form the horsetail termination of the Main Recent fault and may be seen as the propagating southeastern front of the fault system that accommodates indentation of Eurasia by Arabia.

International audience; P>The Kopeh Dagh is accommodating a large portion of the northward motion of central Iran with respect to Eurasia, involving a major right-lateral strike-slip fault system (Bakharden-Quchan). This fault system corresponds to the northeastern boundary of the Arabia-Eurasia collision, and can be considered as a lithospheric-scale tectonic feature. We present a well-constrained estimation of late Quaternary slip rates along two major strike-slip faults (the Baghan and Quchan faults) in this fault system, using in situ-produced Cl-36 nuclide to date two offset alluvial fan surfaces. Combining detailed satellite image and digital topographic data analyses complemented with geomorphic fieldwork allows quantifying the cumulative offset values of 940 +/- 100 and 360 +/- 50 m of the fan surfaces along the Baghan and Quchan faults, respectively. A total of 12 carbonate boulders from the fan surfaces were collected and dated. This yields minimum age of two episodes of fan abandonment at 280 +/- 16 (Baghan fault) and 83 +/- 4 ka (Quchan fault). Age estimates and measured offsets of the fans are consistent with respective maximum long-term fault slip rates of 2.8 +/- 1.0 and 4.3 +/- 0.6 mm yr(-1) for the Baghan and Quchan faults over the Middle-Late Pleistocene. Applying the slip rates to cumulative post-folding offsets along the Baghan and Quchan faults indicates that strike-slip motion within the Kopeh Dagh may have started similar to 4 Ma. This constrains the timing of a major tectonic reorganization in the Kopeh Dagh, previously recorded through Arabia-Eurasia collision between 3 and 7 Ma. At the regional scale, the sum of total cumulative strike-slip offsets is about 35-40 km, which implies a total maximum slip rate of about 9 +/- 2 mm yr(-1) in the Central-Eastern Kopeh Dagh. This is resolved to average northward and westward slip rates of similar to 8 and similar to 4 mm yr(-1), respectively, for the Western Kopeh Dagh with respect to Eurasia. Our results also suggests that the localized strike-slip faulting in the Central Kopeh Dagh can be considered as an intercontinental movement between northeast Iran and Eurasia, accommodating about 80 per cent of northward motion of central Iran with respect to Eurasia.