Trench Studies Research Articles

Magnitudes and surface rupture lengths of paleo-earthquakes at the NW-part of the Peel Boundary fault zone, Roer Valley Rift System

The Peel Boundary Fault zone (PBFZ) is the 125 km long, seismically active, northern bounding fault zone of the Roer Valley Rift System (RVRS). The last damaging earthquake along the PBFZ was the Roermond earthquake of 1992. It had a magnitude of Mw 5.3 and no surface rupture. Previous results from two trenching studies located in the central and southeastern parts of the PBFZ provided evidence for two surface rupturing paleo-earthquakes. The largest earthquake had an estimated magnitude of Mw ∼6.8 and a surface rupture length of at least 35 km. As it took place around the Late Pleniglacial – Late Glacial transition a link to glacio-isostatic motions is likely. Results from a new trench situated at the northwestern part of the PBFZ shows evidence for three to four paleo-earthquakes, of which three were surface rupturing. These comprise two normal faulting- and one, younger trans-tensional displacement. The normal faulting events have ∼1 m vertical displacements each, which translate into magnitudes of Mw ∼7. Like the previous results, they occurred during the Late Pleniglacial-Late Glacial transition, at ∼15 ka and ∼ 14 ka. The younger trans-tensional event occurred sometime during the Holocene, pre-dating an unaffected, 13th century man-made paleo-channel on the hangingwall. The potential fourth, non-surface rupturing earthquake is indirectly evidenced by loading deformations of a sand layer and a collapsed brick-wall in the infill of the paleo-channel. Comparison of our trenching results to those from the two previous studies, which were located farther to the southeast along the PBFZ, shows that for one event a correlation is possible. The correlation would indicate a surface rupture length of at least 55 km. Combined, all trenching results indicate that the characteristic maximum rupturing displacement is ∼1 m, and thus that Mw ∼7 is the maximum magnitude of paleo-earthquakes along the PBFZ.

Geometry, slip rate, and the latest earthquake of the Jinta Nanshan Fault: Interactions of the Altyn Tagh Fault and the Qilian Shan at the northern margin of the Tibetan Plateau

This work presents a study of late Quaternary activity on the Jinta Nanshan Fault (JTF), to constrain its properties including seismic hazard, and to understand the tectonic evolution of the northern edge of the Tibetan Plateau. The JTF has developed during northeastward growth of the Qilian fold-and-thrust belt and eastward growth of the Altyn Tagh Fault. Based on remotely-sensed image interpretation and field investigation, trench studies, high-resolution terrain construction and Optical Stimulated Luminescence dating, we study the fault geometry and slip motion, and constrain the slip rate and the latest earthquake for the JTF. The JTF continues as far southeast as the Heihe River and shows predominantly left-lateral strike-slip displacement. The left-lateral slip rate is 0.27–0.48 mm/yr since late Pleistocene, much larger than the vertical slip rate of 0.05 ± 0.01 mm/yr. The latest rupture event of the JTF is slightly before 1 ka, which could be related to the poorly-recorded 756 CE earthquake in Hexi Corridor, and is also associated with fresh offset during this earthquake in the geomorphology of the east segment of the JTF. Strike-slip offset in this earthquake is estimated as 3.2 ± 0.4 m, with a rupture length of at least ∼13 km, indicating a moment magnitude of 6.4–7.2. We estimate the recurrence interval as 8–13 ka, based on the size of the latest offset and the slip rate of 0.27–0.48 mm/yr. These results indicate that the strike-slip continuation of the Altyn Tagh Fault dominates the slip behaviour of the JTF. The small strike-slip rate, and the match between the strike-slip of the JTF and the vertical slip of the North-South Normal Faults (NSF) at its eastern end, permit the interpretation that the slip of Altyn Tagh Fault is completely accommodated by crustal extension at the NSF, and dies out at the eastern end of the Jinta Nanshan region.

A Novel Approach for Reconstructing Slip Histories for Bedrock Fault Scarps Using Rock Surface Luminescence Dating

AbstractA newly developing method, optically stimulated luminescence (OSL)‐depth profiles (DPs), provides a novel means of reconstructing and quantifying fault slip on timescales of 101−4 years. A targeted bedrock fault scarp along Langshan in north China, used as proof of concept, is divided into four sections based on four groups of OSL‐DPs at different heights up the bedrock fault scarp. These have seismic displacements of 170, 80, 130, and 140 cm, and without considering the erosion rate, the exposure ages at the four displacements are 6–35 a, 19–84 a, 0.5–0.9 ka, and 2–5 ka, respectively. The ages are overall in chronological order, while the actual ages are likely underestimated due to erosion. After assuming erosion amounts according to the weathering characteristics, the calculated ages are mostly consistent with paleoseismic trenching studies. In addition, the method may identify a seismic event that previous studies did not identify.

New Insights Into the Paleoseismic History of the Mae Hong Son Fault, Northern Thailand

The Mae Hong Son Fault (MHSF) is a north-trending active fault in northern Thailand. The largest earthquake ever recorded in Thailand occurred in February 1975 with a magnitude of 5.6 and was associated with the southern end of the MHSF. Paleoearthquake magnitudes, recurrence intervals, and slip rates for the MHSF are evaluated using the morphological characteristics of the MHSF aided with a 12.5-m-resolution digital elevation model (DEM) and using fault trenching. Morphotectonic analysis, including studies of offset streams, linear valleys, triangular facets, and fault scarps, helps illustrate dextral fault movements within the MHSF zone. Two separated N–S trending basins, the Mae Hong Son to the north and the Mae Sariang to the south, are present along the MHSF. Between these basins, fault displacements decrease toward the Khun Yuam area. Surface rupture length investigation from fault segments in both basins indicates maximum credible earthquake magnitudes between 5.8 and 6.3. Fault trenching and road-cut studies show that nine earthquakes occurred along the MHSF over the past ∼43 ka. Optically stimulated luminescence (OSL) dating help define the timing of the earthquakes to ∼43, ∼38, ∼33, ∼28, ∼23, ∼18, ∼13, ∼8, and ∼3 ka. The recurrence interval of earthquakes on the Mae Hong Son Fault is ∼5,000 years and the fault has a slip rate of ∼0.04–0.15 mm/a.

Fault Activation in Central Mongolia during the Holocene: Results of Study of the Mogod Earthquake Ruptures

Abstract —In order to determine the seismotectonic activity of faults in the Holocene, we performed trench studies of the ruptures produced by the catastrophic Mogod earthquake (5 January 1967, M = 7.5–7.8, I0 = 9–10) in the junction zone of the N–S striking Hulzhin Gol fault and the NW striking Tullet fault. Paleoseismic interpretation of seismic-deformation sections and radiocarbon dating of the samples allowed determining the kinematics and obtaining, for the first time, the absolute ages of paleoevents preceding the Mogod earthquake. Analysis of the tectonic conditions for realization of earthquake sources has shed light on the complex structure of ruptures in the area of the Mogod earthquake epicenter, within which three segments differing in the displacement amplitudes and kinematics have been identified. The research data indicate the repeated activation of the Tulet and Hulzhin Gol faults in the Late Pleistocene–Holocene. The absolute age of the latest activation is 596–994 AD for the Tulet fault and 11,379–6235 BC for the Hulzhin Gol fault. The cumulative deformation from paleoearthquakes in the trench sections in the Tulet fault zone points to at least two displacements of thrust kinematics, with the latest of them having an amplitude of 2.8 m. The paleoearthquake in the Hulzhin Gol fault zone is characterized by the presence of lateral slip. The amplitudes of deformations attest to earlier earthquakes similar in energy to the 1967 Mogod event or even stronger in the fault node. The obtained data on the timing of these earthquakes and the amplitudes of the accompanying displacements made it possible to estimate slip rates along the faults: 0.2–0.3 m/kyr horizontal-slip rates on the Hulzhin Gol fault and 0.5–0.7 m/kyr vertical-slip rates on the Tulet fault.

Middle to Late Pleistocene faulting history of the Heerlerheide fault, Roer Valley Rift System, influenced by glacio-isostasy and mining-induced displacement

Faults of the Roer Valley Rift System (RVRS) are characterized by seismicity, scarps and displaced fluvial terraces, showing that they are active. The Heerlerheide fault is part of the southern boundary fault system of the RVRS, the Feldbiss fault zone (FFZ). During the late 19th and first half of the 20th century coal was mined in the subsurface south of the FFZ. As a result, general subsidence, sinkholes, and fault scarplets appeared on the surface. One of the induced fault scarps coincides with the location of the Heerlerheide fault, indicating that the upper part of the fault was reactivated by the mining. A trench was opened across the fault to study the mining-induced fault reactivation as well as the tectonic fault displacement history.The Heerlerheide fault offsets a 340 ka Meuse river terrace overlain by loess and loess-like deposits of Eemian to Late Pleniglacial age, including the Rocourt soil, the Eben/Patina discordance and the Nagelbeek soil complex. At least three tectonic faulting events were reconstructed, which are most likely surface rupturing earthquakes. However, the two oldest displacements could represent multiple faulting events. The age of the youngest event is well constrained between 17 and 15 ka. The duration of the time interval between the penultimate and youngest events is at least 8 ky (the inter-event time is an important parameter for assessing seismic hazard). The vertical coseismic displacement of the youngest event was around ∼0.25 m; the estimated moment magnitude is around 6.2. This event is more or less synchronous with the age of events found in other fault trench studies of the FFZ. The timing is roughly contemporaneous with surface rupturing earthquakes along the northern boundary fault zone of the RVRS, the Peel Boundary fault zone (PBFZ), and a phase of volcanism in the nearby Eifel area, suggesting a common mechanism. The timing also corresponds to the start of the glacio-isostatic forebulge collapse, which has been invoked before to explain earthquake events in the RVRS, and in northern Germany and Denmark.Previous studies provided evidence for a Holocene surface rupturing earthquake with an offset of about 1 m at the Geleen fault in the Meuse valley on Belgian territory, taking place between 2.5 ± 0.3 and 3.1 ± 0.3 ka. The Geleen and Feldbiss faults on Dutch territory experienced faulting during the Late Glacial – Holocene. The incision and deposition history of a brook crossing these faults suggests an age around 7.5 ka for this event. However, in contrast, our results for the Heerlerheide fault show no evidence for Late Glacial – Holocene tectonic fault activity.We also observed 0.34 m of vertical displacement of the base of the plough layer, which corresponds to the amount to what was observed at the surface during the mining in 1936, indicating that no fault motions have occurred afterwards, despite re-flooding of the mines and consequent surface rebound. However, the fact that the fault was reactivated by subsurface mining shows that it is a weakness zone in the subsurface, and therefore fault reactivation might occur due to still ongoing rebound. In contrast to the tectonic fault displacement, the mining-induced offset was accompanied by downslope movement of the upper part of the hanging wall, resulting in splaying of the fault tip and crack formation.

Event-dominated transport, provenance, and burial of organic carbon in the Japan Trench

The delivery of organic carbon (OC) to the ocean's deepest trenches in the hadal zone is poorly understood, but may be important for the carbon cycle, contain crucial information on sediment provenance and event-related transport processes, and provide age constraints on stratigraphic sequences in this terminal sink. In this study, we systematically characterize bulk organic matter (OM) and OC signatures (TOC/TN, δ13C, 14C), as well as those from application of serial thermal oxidation (ramped pyrolysis/oxidation) of sediment cores recovered along an entire hadal trench encompassing high stratigraphic resolution records spanning nearly 2000 years of deposition. We analyze two cores from the southern and northern Japan Trench, where submarine canyon systems link shelf with trench. We compare results with previously published data from the central Japan Trench, where canyon systems are absent. Our analyses enable refined dating of the stratigraphic record and indicate that event deposits arise from remobilization of relatively surficial sediment coupled with deeper erosion along turbidity current pathways in the southern and central study site and from canyon flushing events in the northern study site. Furthermore, our findings indicate deposition of predominantly marine OC within hemipelagic background sediment as well as associated with event deposits along the entire trench axis. This implies that canyon systems flanking the Japan Trench do not serve as a short-circuit for injection of terrestrial OC to the hadal zone, and that tropical cyclones are not major agents for sediment and carbon transfer into this trench system. These findings further support previous Japan Trench studies interpreting that event deposits originate from the landward trench slope and are earthquake-triggered. The very low terrestrial OC input into the Japan Trench can be explained by the significant distance between trench and hinterland (>180 km), and the physiography of the canyons that do not connect to coast and river systems. We suggest that detailed analyzes of long sedimentary records are essential to understand OC transfer, deposition and burial in hadal trenches.

Late Miocene to Quaternary Development of the Jiujing Basin, Southern Beishan Block, China: Implications for the Kinematics and Timing of Crustal Reactivation North of Tibet

AbstractWe present results from a multidisciplinary investigation of the Jiujing fault (JJF) system and adjacent Jiujing Basin in the southern Beishan block, western China. Structural and geomorphological fieldwork involving fault and landform investigations, remote sensing analysis of satellite and drone imagery, analysis of drill-core data, paleoseismological trench studies, and Quaternary dating of alluvial sediments suggest the JJF is a late Pleistocene to Holocene oblique sinistral-slip normal fault. Satellite image analysis indicates that the JJF is a connecting structure between two regional E-W-trending Quaternary left-lateral fault systems. The Jiujing Basin is the largest and best developed of three parallel NE-striking transtensional basins within an evolving sinistral transtensional duplex. Sinistral transtension is compatible with the orientation of inherited basement strike belts, NE-directed SHmax, and the modern E-NE-directed geodetic velocity field. Cosmogenic 26Al/10Be burial dating of the deepest sediments in the Jiujing Basin indicates that the basin began to form at ~5.5 Ma. Our study reveals a previously unreported actively deforming domain of transtensional deformation 100 km north of Tibet in a sector of the Beishan previously considered tectonically quiescent. Recognition of latest Miocene-Recent crustal reactivation in the Jiujing region has important implications for earthquake hazards in the Beishan and western Hexi Corridor/North Tibetan foreland sectors of the Silk Road Economic Belt. Additionally, we compare the timing of latest Miocene-Recent crustal reactivation in the southern Beishan with the documented onset of reactivation in other deforming regions north of Tibet.

Transitions in microbial communities along two sediment cores collected from the landward walls of the New Britain trench

The landward wall of the New Britain Trench (NBT) is an active continental margin. Unlike passive margins, it lacks a continental rise and the abyssal plain, and has a steep continental slope ending in an oceanic trench. Although the trench systems are receiving more and more attentions, our understanding of the microbiology of the NBT and its trench walls is limited. In this study, we collected a 70 cm gravity core (4524 m depth) and a 30 cm box core (4130 m depth) from the western and eastern landward walls of the NBT, respectively. Diversity and composition of microbial communities were investigated at high resolution in 2 cm depth intervals. In two cores, obvious vertical transitions from the aerobic to anaerobic but distinct dominant anaerobic microbes were observed. In the eastern trench wall, anaerobic fermenters, such as Anaerolineales and Alphaproteobacteria, were dominant, but the western contained abundant Dehalococcoidia, and Gammaproteobacteria, such as Alteromonadales and Oceanospirillales. Combined with the results of higher bacteria abundance and probable shallower aerobic active zone in the eastern core, such patterns of species composition might be related with richer input of labile allochthonous terrestrial organic matter by mass wasting processes in the steeper eastern wall. Our analysis also revealed highly diversified Dehalococcoidia including some new phylotypes, extending the current understandings on Dehalococcoidia diversity. This study fills the gap of benthic microbial study in the NBT, and highlights the need of multi-point sampling in trench studies for the great geographical variations along the trench wall.

A Late Glacial surface rupturing earthquake at the Peel Boundary fault zone, Roer Valley Rift System, the Netherlands

Paleoseismological trenching studies constrain recurrence times and magnitudes of faulting events and earthquakes on active faults. In a trench along the central part of the Peel Boundary fault zone (PBFZ), southeastern Netherlands, evidence was found for such a large faulting event that occurred around 14 ka. The event caused a fault scarp in unconsolidated sediments of ∼1 m height. A colluvial wedge was formed next to the scarp. A second faulting event offsets this colluvial wedge by 0.2–0.1 m. This event can be tentatively dated at ∼13 ka. During or immediately after the second event, a large clastic dyke intruded along the fault plane. The dyke is not faulted, but its emplacement did cause some minor thrust faulting around the injection.The sudden character of the main faulting event, the brittle deformation style of loam layers, the lack of growth faulting in the colluvial wedge, the clastic dykes and the flame structures demonstrate that the main faulting event was a surface rupturing earthquake. Based on the scarp height, the estimated moment magnitude is about 6.8 ± 0.3. Similar observations in a previous trench site suggest that the length of the surface rupture was at least 32 km. The earthquake took place during the Weichselian (Würmian) Late Glacial. This timing corresponds to the start of the glacio-isostatic forebulge collapse in the Netherlands. Glacio-isostatic movements have been invoked before to explain earthquake events in the Roer Valley Rift System in which the PBFZ is situated, and in northern Germany and Denmark. If these earthquakes can indeed be attributed to a collapsing forebulge, their ages should show a decrease in the direction of ice-sheet retreat. This might indeed be the case, as the ages decrease from 14 ka and 13 ka in this trench via 13–16 ka at the Osning Thrust Zone, NW Germany, to 12–14 ka in northern Denmark.

Are U‐Th Dates Correlated With Historical Records of Earthquakes? Constraints From Coseismic Carbonate Veins Within the North Anatolian Fault Zone

AbstractU‐Th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late Quaternary crustal deformations. In this study, for the first time we correlate U‐Th ages of travertine deposits in coseismic fissures along the North Anatolian Fault Zone with records of paleoseismological studies supported by historical earthquake catalogued data. U‐Th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major Holocene earthquakes. Our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the North Anatolian Fault Zone. The periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies. At least six of the periods correspond to the earthquakes reported in the historical catalogues. The age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern North Anatolian Fault Zone with a mode at 130–330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault. Recorded events in carbonate veins indicate a close‐epicenter (d < 200 km) and high‐intensity (I > VI) paleoearthquakes. Our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques. This tool has advantages over traditional paleoseismological methods for the understanding of long‐term earthquake behavior, particularly for prehistoric late Pleistocene events which cannot be dated easily by traditional paleoseismological methods.

Paleoseismological Catalog of Pre-2012 Trench Studies on the Active Faults in Turkey

Paleoseismological Catalog of Pre-2012 Trench Studies on the Active Faults in Turkey

Earth fissures in Qinglong Graben in Yuncheng Basin, China

Qinglong Graben is located in southeastern Yuncheng Basin, China flanked by two north-east trending normal faults, where the geological condition is favourable for generating earth fissures. Since 1978, five earth fissures have formed in Qinglong Gaben. In the present work, a series of geological investigation consisting of site investigation, geological drilling and trench excavation was used to characterise and determine the reasons for the formation of the earth fissures. The site investigation indicated that the trend of the five earth fissures are parallel to the general strike of the normal fault, i.e., geological drilling and trench studies revealed that syn-sedimentary fault is the key reason for the formation of the earth fissures. Additionally, over-exploitation of groundwater and erosion process are important factors in the development and expansion of the earth fissures in Qinglong Graben. The earth fissures forming process in Qinglong Graben can be divided into three stages: the regional extension first caused normal faults under the surface, and then the pumping action of excessive groundwater induced the normal faults propagate to the surface, and finally the erosion promoted the formation of the current earth fissure.

Palaeoseismic history of the eastern part of the North Anatolian Fault (Erzincan, Turkey): Implications for the seismicity of the Yedisu seismic gap

The North Anatolian Fault showed a remarkable seismic activity especially between 1939 and 1999, when the westward migrating earthquake sequence created surface ruptures more than 1000 km, leaving unbroken only the Marmara segments, to the west, and the Yedisu Segment, to the east along the main strand of the fault. To understand the palaeoseismicity of the Yedisu Seismic Gap, we undertook trench investigations close to the village of Balaban Sarikaya, on the western part of the Yedisu Segment. We found evidence for at least five surface faulting earthquakes, from which only two are correlated with the 18 July 1784 CE and 27 June 1583 CE historical events. Although the surface rupture of the 1784 CE was reported by other trench studies, the evidence of 1583 CE event is presented for the first time. In consideration with other historical earthquakes, affecting the region east of Erzincan, we suggest that this particular section of the North Anatolian Fault may be in a seismically quiescent period, following a cluster of earthquakes in its near history. In order to test this hypothesis, further studies are needed to increase our knowledge on the temporal and spatial seismic behaviour of the Yedisu Segment, which has potential to create an earthquake with M w ~7.2 in the near future.

The Manyas fault zone (southern Marmara region, NW Turkey): active tectonics and paleoseismology

The Manyas fault zone (MFZ) is a splay fault of the Yenice Gönen Fault, which is located on the southern branch of the North Anatolian Fault System. The MFZ is a 38 km long, WNW–ESE-trending and normal fault zone comprised of three en-echelon segments. On 6 October 1964, an earthquake (Ms = 6.9) occurred on the Salur segment. In this study, paleoseismic trench studies were performed along the Salur segment. Based on these paleoseismic trench studies, at least three earthquakes resulting in a surface rupture within the last 4000 years, including the 1964 earthquake have been identified and dated. The penultimate event can be correlated with the AD 1323 earthquake. There is no archaeological and/or historical record that can be associated with the oldest earthquake dated between BP 3800 ± 600 and BP 2300 ± 200 years. Additionally, the trench study performed to the north of the Salur segment demonstrates paleoliquefaction structures crossing each other. The surface deformation that occurred during the 1964 earthquake is determined primarily to be the consequence of liquefaction. According to the fault plane slip data, the MFZ is a purely normal fault demonstrating a listric geometry with a dip of 64°–74° to the NNE.

Integrated geophysical investigations in a fault zone located on southwestern part of İzmir city, Western Anatolia, Turkey

Integrated geophysical investigations consisting of joint application of various geophysical techniques have become a major tool of active tectonic investigations. The choice of integrated techniques depends on geological features, tectonic and fault characteristics of the study area, required resolution and penetration depth of used techniques and also financial supports. Therefore, fault geometry and offsets, sediment thickness and properties, features of folded strata and tectonic characteristics of near-surface sections of the subsurface could be thoroughly determined using integrated geophysical approaches. Although Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) methods are commonly used in active tectonic investigations, other geophysical techniques will also contribute in obtaining of different properties in the complex geological environments of tectonically active sites. In this study, six different geophysical methods used to define faulting locations and characterizations around the study area. These are GPR, ERT, SRT, Very Low Frequency electromagnetic (VLF), magnetics and self-potential (SP). Overall integrated geophysical approaches used in this study gave us commonly important results about the near surface geological properties and faulting characteristics in the investigation area. After integrated interpretations of geophysical surveys, we determined an optimal trench location for paleoseismological studies. The main geological properties associated with faulting process obtained after trenching studies. In addition, geophysical results pointed out some indications concerning the active faulting mechanism in the area investigated. Consequently, the trenching studies indicate that the integrated approach of geophysical techniques applied on the fault problem reveals very useful and interpretative results in description of various properties of faulting zone in the investigation site.

Knickpoint series of gullies along the Luoyunshan Piedmont and its relation with fault activity since late Pleistocene

The authors surveyed the longitudinal profiles of 28 gullies across the Luoyunshan Piedmont fault (LPF) by differential GPS and dating of sediments well preserved in the typical terraces and obtained 6-level knickpoint series of the gullies along the Luoyunshan Piedmont. The authors compared it with previous studies on the paleo-earthquakes of the LPF revealed by trenches and found that the paleo-earthquake events from knickpoint and trench studies are in good agreement in terms of the time of occurrence and vertical displacement of the fault. It shows studying the paleo-earthquake events of the fault by knickpoint series is feasible. At last, the authors established a more complete paleo-earthquake sequence of the LPF supported by geomorphologic and sedimentary evidence, i.e., six paleo-earthquake events happened on the LPF from about 28,000years ago; the LPF has the characteristic of quasi-periodic recurrence and the average recurrence interval is 4585years. The vertical displacement of the paleo-earthquake events is 2.4–3.0m; according to the empirical equations between co-seismic displacement and earthquake magnitude the magnitude of these events is Ms 7.0–7.5. This study aims to complement and improve the traditional trenching method, provide theoretical and methodological support for the research of active tectonics, and contribute important information for the seismic hazard assessment of the densely populated Linfen area.

Late Pleistocene - Holocene slip history of the Langshan-Seertengshan piedmont fault (Inner Mongolia, northern China) from cosmogenic 10Be dating on a bedrock fault scarp

Offset geomorphic features and deformed late Quaternary strata indicate active deformation along theLangshan-Seertengshan piedmont fault(LSPF), one of the most active faults in the Hetaofault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic 10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 ka and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10+0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.

The bounding-surfaces record of a barrier spit from Huangqihai Lake, North China: implications for coastal barrier boundary hierarchy

Ground-penetrating radar and trenching studies of a barrier spit on the north shore of Huangqihai Lake were made, that reveal important implications for the coastal washover barrier boundary hierarchy and interpretations of this depositional record. A four-fold hierarchy bounding-surface model, representing different levels of impact and genesis, is defined. Each level of the hierarchy is enclosed by a distinct kind of surface characterized by different ground-penetrating radar reflection features, sedimentary characteristics (color, grain size, sorting, rounding and sedimentary structures) and origin. We suggest that this hierarchical model can be applied to any coastal washover barrier deposits.

Seismites from a well core of palustrine deposits as a tool for reconstructing the palaeoseismic history of a fault

The Concud Fault is located at the junction between the Jiloca and Teruel grabens (central-eastern Iberian Chain, Spain). The Late Pleistocene activity of this fault has been well logged from structural and palaeoseismological trench studies, but only scattered data of the Late Pliocene seismic activity exist. The Late Pliocene–Early Pleistocene syn-tectonic infill consists of an endorheic continental succession in which a75 m-long continuous well was drilled near the Concud Fault. Along the entire well core, several types of soft-sediment deformation structures with variable morphology, size and frequency have occurred including clastic dykes, load structures and slumps. The rigorous analysis of the deformation structures, their relationships with the involved sedimentary facies, and the discrimination of possible deformation mechanisms and trigger processes allow us to interpret part of them as seismically-induced structures. The recognition of 21 deformed beds (seismites) allow the Late Pliocene–Early Pleistocene seismic history of the Concud Fault to be reconstructed. Therefore, 21 seismic events (with M≥5) and an apparent recurrence period of about 45ka have been inferred.