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Identification of the processes producing soft‐sediment deformation structures, common in siliciclastic deposits and less abundant in carbonate successions, is complex, because different processes may produce similar structures. Thus, interpreting the origin of these structures may be challenging: it requires both a detailed sedimentological study, and the knowledge of the depositional environment and stratigraphic evolution, in order to provide hints to identify the processes affecting sediments after deposition. Among the potential causes of the formation of soft‐sediment deformation structures, seismic shock is one of the possibilities, but their origin could be also related to other triggering mechanisms, such as volcanic activity, sediment loading, salt tectonics, fluid expulsion, meteorite impacts and mass movements. Although it is a plausible option, the interpretation of these structures as 'seismites' is not obvious: it must be supported by different lines of evidence, considering that the correct interpretation of soft‐sediment deformation structures as a consequence of seismic shocks acquires important implications in palaeoseismology studies. The occurrence of diverse soft‐sediment deformation structures in a fault‐controlled basin (i.e. in a geological setting characterized by syndepositional tectonics) preserved in different subenvironments of a Norian carbonate system in the Southern Alps of Italy provides the chance to characterize different types of soft‐sediment deformation structures along a platform‐to‐basin depositional profile. Presence of pseudonodules in basinal resedimented limestone, sedimentary dykes and clinostratified breccias with unlithified clasts in slope settings and liquefaction of inner platform facies at the platform top testify to an origin compatible with multiple seismic shocks, repetitively affecting the same stratigraphic intervals. The diverse types of soft‐sediment deformation structures in the studied carbonate system provide a rich catalogue of structures related to seismic shocks, representing a possible reference for other similar settings. [ABSTRACT FROM AUTHOR]

The western Qaidam Basin, NE Tibet contains numerous NW‐SE‐trending thrusts that extend over a distance of ∼300 km along the Altyn Tagh Fault and north of the Kunlun Range. However, little is known about the long‐term seismo‐tectonic evolution of this active thrust zone due to the absence of an extended paleoseismic record. We present a 2‐Myr‐long disturbance record established from a core drilled on the crest of a thrust‐cored anticline. Based on detailed sedimentological analysis, the disturbances (micro‐faults, soft‐sediment deformation, slumps, and detachment surfaces) are interpreted as paleoearthquake/tectonic indicators. The core records five seismite clusters which occurred at 3.6‐3.5, 3.4‐3.2, 3.15‐3.1, 3.0‐2.9, and 2.8‐2.75 Ma. This suggests the rate of tectonic strain accommodated by the folds and thrusts in the region varies and thus reveals episodic local deformation. During the clusters, regional deformation is concentrated more in the fold‐and‐thrust system than along regional major strike‐slip faults. Plain Language Summary: The generally NW‐SE‐trending thrusts developed north of the Kunlun Range are the most prominent morphological feature in the western Qaidam Basin, NE Tibet. These folds have played a key role in the Miocene‐Quaternary uplift of the region. However, little is known about the long‐term rupture behavior of this active thrust zone due to the absence of an extended paleoseismic record. Our understanding of earthquake history is still limited by short seismological and historical records. A continuous lacustrine sedimentary sequence (∼33‐1.6 Ma) accumulated in the Qaidam paleolake which may have sequentially recorded the development and activities of the underlying folds and thrusts. Here, we present a unique record of disturbance spanning 2‐Myr based on a deep core drilled on the crest of one such fold in the western Qaidam Basin. The disturbances comprise micro‐faults, soft‐sediment deformation, slumps, and detachment surfaces. We interpret the four types of disturbance as seismites. The 2‐Myr‐long seismite sequence records five paleoseismic clusters that occurred between 3.6 and 2.7 Ma, suggesting episodic late Pliocene deformation in the western Qaidam Basin, NE Tibet. Key Points: We interpret micro‐faults, soft‐sediment deformation, slumps, and detachment surfaces as paleoearthquake/tectonic indicatorsThe core records five seismite clusters between 3.6 and 2.7 Ma, revealing episodic thrusting in relation to intense regional deformationDuring the clusters, regional deformation was concentrated more in the fold‐and‐thrust system than along regional major strike‐slip faults [ABSTRACT FROM AUTHOR]

The seismic origin of turbidites is verified either by correlating such layers to historic earthquakes, or by demonstrating their synchronous deposition in widely spaced, isolated depocenters. A historic correlation could thus constrain the seismic intensity required for triggering turbidites. However, historic calibration is not applicable to prehistoric turbidites. In addition, the synchronous deposition of turbidites is difficult to test if only one deep core is drilled in a depocenter. Here, we propose a new approach that involves analyzing the underlying in situ deformations of prehistoric turbidites, as recorded in a 457 m‐long core from the Dead Sea center, to establish their seismic origin. These in situ deformations have been verified as seismites and could thus authenticate the trigger for each overlying turbidite. Moreover, our high‐resolution chemical and sedimentological data validate a previous hypothesis that soft‐sediment deformation in the Dead Sea formed at the sediment‐water interface. Plain Language Summary: Seismogenic turbidites are widely used for geohazard assessment. The use of turbidites as an earthquake indicator requires a clear demonstration that an earthquake, rather than non‐seismic factors, is the most plausible trigger. The seismic origin is normally verified either by correlating the turbidites to historic earthquakes, or by demonstrating their synchronous deposition in widely spaced, isolated depocenters. The correlated historic earthquakes could thus constrain the seismic intensities necessary for triggering turbidites. However, the historic correlation method is not applicable to prehistoric turbidites. In addition, the synchronous deposition of turbidites cannot be verified if only one deep core is drilled in a depocenter. Here, we propose a new approach to constrain the seismic origin for prehistoric turbidites in a deep core from the Dead Sea center. Moreover, we constrain the seismic intensities that triggered prehistoric turbidites by analyzing the degree of in situ deformation underlying each turbidite. In addition, we use our results to propose seven basic earthquake‐related depositional scenarios preserved in depocenters located in tectonically active regions like the Dead Sea. These techniques and findings permit a more confident geohazard assessment in the region and other similar tectonic settings by improving the completeness of a paleoseismic archive. Key Points: Seismic origin for prehistoric turbidites is established by analyzing the underlying in situ deformation structures for each turbiditeData validate a previous hypothesis that soft‐sediment deformation formed at the sediment‐water interface in the Dead SeaThe new approach permits a more confident geohazard assessment by improving the completeness of a paleoseismic archive [ABSTRACT FROM AUTHOR]

Cores from the middle Eocene sediments of the Dongying Depression of the southern Bohai Bay Basin in east China yield various kinds of sedimentary deformation structures. They include microfolds, load casts, flame structures, ball-and-pillow structures, load-cast ripples, pinch-and-swell structures, boudinage structures, sand dikes, microfaults, and cataclastic breccias. Gravity flows, including turbidites and debris flows, also occur in the study area. The deformation layers can be divided into plastic deformation and brittle deformation types. These develop in a succession composed mainly of dark finely laminated and massive mudstone interbedded with thin sandstones and carbonate rocks that accumulated in a low-energy semi-deep to deep lacustrine environment in a tectonically active setting. Considering the facies attributes in the study area, intrinsically possible trigger mechanisms such as rapid sediment loading and storm currents are absent. Thus, the sedimentary deformation features should be induced by seismic activity, and the same with the gravity flows. These seismites are interpreted to have originated from earthquakes with magnitudes exceeding M 5.6. Basin-controlling faults in the north border of Dongying Depression give rise to the occurrence of seismites. The increasing occurrence frequency of seismites from Es4u to Es3l corresponds with the increase in the activity velocity of the basin-controlling faults. Compared with the seismites developed in other fault depressions in the Bohai Bay Basin, seismites developed in the Dongying Depression are relatively smaller scale and are dominated by microfault layers, relatively more cohesive sediments, and greater distance between seismites and active faults results in the occurrence of these features. [ABSTRACT FROM AUTHOR]

The southern part of the Eastern Anatolian Plateau is a key region for understanding the tectonic activity and related deformation patterns of the Arabian–Eurasian collision zone. The geological record of seismic events collected from lacustrine deposits of Lake Van Basin is a critical requirement for seismic hazard assessment and seismic risk reduction. Our paleoseismic investigations revealed well-preserved seismites at five locations in late Pleistocene lacustrine deposits. The seismites were dated using an optically stimulated luminescence dating method and were arranged according to their ages. Their type, such as convolute, dish-and-pillar, flame, and ball-and-pillow structures, as well as their locations, ages, and stratigraphic distribution enable us to identify the responsible fault and the earthquake recurrence interval. On the basis of these properties, the Erciş Fault has been recognized as the structure responsible for creating the seismites. The time span between the seismites indicates an apparent earthquake recurrence interval of 125–250 years for large earthquakes (M ≥ 5) related to the Erciş Fault. The method applied here enriches our knowledge on the seismic hazards present in the northern Lake Van region. • Quaternary lacustrine deposits of the Lake Van Basin contain different types of seismites. • Seismites include convolute, dish-and-pillar, flame, and ball-and-pillow structures. • Seismites were formed by dextral strike-slip the Erciş Fault. • Earthquake-recurrence period for the Erciş Fault is determined as 125–250 years with OSL-dating of seismites. [ABSTRACT FROM AUTHOR]

Small lakes in low relief areas are atypical candidates for studies on paleoseismicity, but their sediments can contain seismically induced event layers (seismites) generated through strong ground shaking, sediment transport, hydrological reorganization and/or changes in groundwater chemistry and flow. Lakes Lungo and Ripasottile are shallow lakes (<10 m deep) located in the tectonically active Rieti Basin in the central Apennines, Italy, where strong normal faulting earthquakes (Mw 6.5 to 7.0) regularly occur. Sediment cores from these lakes provide paleoseismic indicators for the past ∼1000 years. Sedimentological and geochemical analysis reveals four event layers identified in both lakes that correspond with documented large-scale earthquakes in 1298, 1349, 1639, and 1703 AD. Chronological correlation between earthquakes and paleoseismic features is reliable because of the resolution of sediment dating available for the studied cores. The common physical structure is a physically homogenous bed (homogenite) of re-suspended sediment consisting of a denser, high magnetic susceptibility (κ) clastic base, with organic matter concentrated above. Co-seismic to post-seismic chemical signatures are associated with some event layers and may represent abrupt or transient shifts to a groundwater-dominated system, or permanent changes in groundwater flow and/or spring discharge. Excursions in δ13C org may represent disruptions or changes in carbon source. Not all event layers show the same features, a result attributed to differences in seismic processes as well as the lake attributes, and anthropogenic modification. The observations made here may provide a new means of detecting paleoseismicity and may be applied to other low relief lakes in seismically active areas. • Review of chemical and sedimentological indicators of paleoseismicity from lakes. • Lakes in low-releif, seismicaly active areas may provide records of past earthquakes. • Generating co-seismc sedimentary signatures depends on lake morphology, connection to groundwater, and earthquake characteristics. [ABSTRACT FROM AUTHOR]

Abstract The Neoproterozoic Kansuki Formation in the Katanga Supergroup (Katanga Copperbelt, Democratic Republic of the Congo) mainly consists of platform carbonates with pyroclastic beds and mafic layers. Lithological and sedimentological investigation in the central part of the Katanga Copperbelt (Tenke Fungurume Mining District) evidenced peritidal facies for the carbonate. It also evidenced the presence of Soft Sediment Deformation Structures (SSDS). Small-scale load structures, multiple successions of load cast and flame structures are attributed to discrete sedimentary processes such as overloading and rapid deposition. Tepee-like structures are indicative of a subaerial exposure of the carbonate that was deposited in relatively shallow water. Major SSDS such as boudinage within water escape structures, load cast with attached pseudonodules, tepee-like structures with sheet cracks, small-scale mass displacement, and brecciation are interpreted as triggered by seismicity and indicative of active tectonics during sedimentation in the Katanga basin. This is consistent with the presence of pyroclastic beds and mafic layers within the Kansuki Formation, pointing to carbonate platform deposition in a paleorift. Highlights • Neoproterozoic carbonate platform in the Katanga Supergroup. • Soft sediment deformation structures associated to the carbonate rocks. • Peritidal facies and arid to semi-arid climate. • Sedimentary origin and seismicity related to the expansion of the Katangan basin. • Active tectonic during the sedimentation. [ABSTRACT FROM AUTHOR]

The Yaojiachezhan (YJCZ) section and NGN1, Zk3389 and SK1-S wells, which are located in the southeastern part of the Songliao Basin, NE China, were used to analyse paleoseismic events recorded in the Upper Cretaceous first member of the Nenjiang Formation. Two representative seismic sequences are recognised in these lacustrine deposits. The seismic sequence observed in the YJCZ section, from the base to top, includes step micro-faulting, seismic fissures, liquefaction sandstone veins, brecelated structures, liquefied fold-deformed laminations and sand pillow structures. Whereas in NGN1 core, from the base to top, includes micro-faulting, seismic fissures, sand pillow structures, liquefied folddeformed laminations and liquefaction sandstone veins. These two seismic sequences together reflect the processes resulting from a strong seismic event from initiation to culmination, then decline and recession. The occurrence of brecciated structures reflects the earthquake magnitude in the YJCZ section area probably reached M7.5, while liquefied fold-deformed laminations in the NGN1 core area reflects an earthquake magnitude of M7.0. Empirical relations between earthquake magnitude and the maximum distance of liquefaction deformation structure sites from the epicentres show that the longest distance between the earthquake source area for the YJCZ section and NGN1 well are <100 km, whereas the distance for the Zk3389 and SK1-S wells is >100 km. The trigger source area for this paleoseismic event is most likely the Yilan-Yitong Fault, meaning that the Yilan-Yitong Fault was active during the deposition of the first member of the Nenjiang Formation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Traces of six large paleoearthquakes in the western Issyk-Kul basin were identified. • Were determined ages and recurrence times of paleoearthquakes. • We found new sequences containing seismites in Issyk-Kul Lake area. • Seismic trigger was suggested for deformations at the Sary-Bulun settlements. • Was established the cause of the break of connection between the Chu River and lake. Abstract New paleoseismological and archaeoseismological data from the western Issyk-Kul basin of Kyrgyzstan (northern Tien Shan) provide new insights on active fault in the actively-deforming, basement-involved thrust system of Central Asia. Newly discovered fault scarps follow south-and north-dipping thrust faults which delineate the Kyrgyz and Kungey ranges bordering the Issyk-Kul basin. Motion on these faults generated earthquakes with magnitudes 6.2–7.6 and MSK-64 shaking intensities VIII-XI. Deformation observed in the zone of the Toguz-Bulak fault results from two Holocene earthquakes and another event that occurred about 8000 yr BP. Two more events, at 13,000 and 3000 yr BP, deformed the northeastern periphery of the Kyzyl-Ompul Uplift. Archaeoseismological research in the Northern Sary-Bulun settlement in the western periphery of the Boz-Barmak Uplift, revealed traces of another earthquake of MSK-64 shaking intensity I ≥ VIII dating back to the 12th Century. The obtained data correlates well with results of previous paleoseismological and archeoseismological studies. They show that in the northern Tien Shan there were clusters of strong earthquakes with ages of 14–13, 8, 4–3 ka ago and in the 11–12th centuries AD divided by periods of 4–5 ka. We infer that coseismic slip on these faults may have formed a tectonic dam at the edge of the basin through growth of the Boz-Barmak Uplift, and this dam ultimately deflected the Chu River into its modern channel which bypasses the lake. Lacustrine sediments in the northeastern periclinal segment of the Boz-Barmak Uplift bear signatures of soft-sediment deformation structures (seismites) corresponding to seven M ≥ 5–5.5 (I ≥ VI-VII) earthquakes timed at about 20,000 yr BP. [ABSTRACT FROM AUTHOR]

Abstract Earthquakes-related soft-sediment deformations (seismites) are relevant structures to help reconstructing the palaeoseismicity in a region. Nevertheless, although seismites have been described for a large variety of palaeo-environments and stratigraphic settings, they are rare and, in some cases, ambiguous structures. In this paper, we document, for the first time, impressive seismites affecting a latest Quaternary travertine deposit located in southern Tuscany (Serre di Rapolano, Italy). These structures are extremely relevant, as seismites have been never described for this kind of terrestrial deposits. The seismites developed within a 2.5 m thick stratigraphic succession made of alternating terrigenous and carbonate sediments, embedded within the travertine deposits. Earthquake produced liquefaction and fluidization of some terrigenous levels and the injection of fluidized silty sediments (dykes and sills) into carbonate and terrigenous levels; slumped levels and associated decollement surfaces produced highly non-cylindrical folds, overall induced by the loss of brittle shear strength along the basin slopes. The occurrence of these soft-sediment deformations implies an important seismic event that took place in a time spam encompassed between 84 ± 8 and 48.92 ± 5.08 ka, in an area characterized by low seismicity and scarce knowledge of its seismotectonic setting. Their spectacular exposition and preservation in saw-cuts of an abandoned quarry (Cava Oliviera quarry) highlights their relevance and importance. Graphical abstract Unlabelled Image Highlights • Soft-sediment deformation structures (SSDS) hosted in travertine deposits have been documented for the first time. • We highlight that SSDS affected a 2.5 meters-thick terrigenous level, interbedded within the carbonate deposit. • We interpret these SSDS as seismites triggered by a M>5 seismic event occurred between 84 ± 8 and 48.92 ± 5.08 ka. • We document late Pleistocene seismicity in the Siena Basin, characterized by low seismicity and scarce knowledge on active faults. • We emphasise the travertine deposits as recorders of palaeo-earthquakes and palaeo-seismicity. [ABSTRACT FROM AUTHOR]

Paleoseismological studies confirm that the Uimon basin is thrust by its northern mountain border along the active South Terekta fault. The latest motion along the fault in the 7-8th centuries AD induced an earthquake with a magnitude of M w = 7.4-7.7 and a shaking intensity of I = 9-11 on the MSK-64 scale. The same fault generated another event (M > 7, I = 9-10), possibly, about 16 kyr ago, which triggered gravity sliding. The rockslide dammed the Uimon valley and produced a lake, where lacustrine deposition began about 14 ± 1 kyr ago, and a later M > 7 (I = 9-10) earthquake at ~ 6 ka caused the dam collapse and the lake drainage. Traces of much older earthquakes that occurred within the Uimon basin are detectable from secondary deformation structures (seismites) in soft sediments deposited during the drainage of a Late Pleistocene ice-dammed lake between 100 and 90 ka and in ~ 77 ka alluvium. The magnitude and intensity of these paleoearthquakes were at least M > 5.0-5.5 and I > 6-7. [ABSTRACT FROM AUTHOR]

Seismite horizons are abundant in Cretaceous sandstones of the Rukwa Rift Basin, southwestern Tanzania. Diverse morphologies of soft-sediment deformation are preserved, including two new, unusual sedimentary structures, herein referred to as 1) balloon-shaped inflation structures and 2) surface fractures with linked sandstone splays. This original description of new sedimentary structures contributes to the growing catalogue of seismically induced deformation features. Their unusual morphologies bring to the forefront an important, though seldom touched upon, question of how to differentiate between gas- and water-escape in soft-sediment deformation features. The recognition of the spectrum of soft-sediment deformation structures contained in strata and their deformational mechanisms is important because it permits the differentiation between triggering mechanisms, particularly seismic activity, and can constrain such events spatially and temporally. We interpret the surface fractures and linked sandstone splays to reflect a high gas effusion rate, formed by the release of high-pressure gas followed by a limited expulsion of water. The balloon-shaped inflation structures reflect lower gas effusion rates due to expulsion of lower pressure gas that did not breach the Cretaceous surface seal. When these gas pulses did breach the paleosurface, they formed gas-discharge pits. These seismogenic structures are consistent with deposition of Cretaceous strata in the Rukwa Rift during periods of active carbonatite volcanism, seismicity, and possibly hot spring activity. This documentation serves as an important data point for the re-examination of the classification scheme of soft-sediment deformation structures as primarily water-escape structures to accommodate for the genesis of some secondary sedimentary features by gas-escape. [ABSTRACT FROM AUTHOR]

This work describes soft-sediment deformation structures (clastic dykes, load structures, diapirs, slumps, nodulizations or mudcracks) identified in three sections (Concud, Ramblillas and Masada Cociero) in the Iberian Range, Spain. These sections were logged from boreholes and outcrops in Upper Pliocene-Lower Pleistocene deposits of the Teruel-Concud Residual Basin, close to de Concud normal fault. Timing of the succession and hence of seismic and non-seismic SSDSs, covering a time span between ~ 3.6 and ~ 1.9 Ma, has been constrained from previous biostratigraphic and magnetostratigraphic information, then substantially refined from a new magnetostratigraphic study at Masada Cociero profile. Non-seismic SSDSs are relatively well-correlated between sections, while seismic ones are poorly correlated except for several clusters of structures. Between 29 and 35 seismic deformed levels have been computed for the overall stratigraphic succession. Factors controlling the lateral and vertical distribution of SSDSs are their seismic or non-seismic origin, the distance to the seismogenic source (Concud Fault), the sedimentary facies involved in deformation and the observation conditions (borehole core vs. natural outcrop). In the overall stratigraphic section, seismites show an apparent recurrence period of 56 to 108 ka. Clustering of seismic SSDSs levels within a 91-ka-long interval records a period of high paleoseismic activity with an apparent recurrence time of 4.8 to 6.1 ka, associated with increasing sedimentation rate and fault activity. Such activity pattern of the Concud Fault for the Late Pliocene-Early Pliocene, with alternating periods of faster and slower slip, is similar to that for the most recent Quaternary (last ca. 74 ka BP). Concerning the research methods, time occurrence patterns recognized for peaks of paleoseismic activity from SSDSs in boreholes are similar to those inferred from primary evidence in trenches. Consequently, apparent recurrence periods calculated from SSDS inventories collected in borehole logs close to seismogenic faults are comparable to actual recurrence times of large paleoearthquakes. [ABSTRACT FROM AUTHOR]

The Shulu Sag, located in the southwestern corner of the Jizhong Depression, Bohai Bay Basin of east China, is a NE–SW trending, elongate Cenozoic half-graben basin. The lowermost part of the third member of the Shahejie Formation in this basin is characterized by continental rudstone and calcilutite to calcisiltite facies. Based on core observation and regional geologic analysis, seismites are recognized in these lacustrine deposits, which include soft-sediment deformation structures (sedimentary dikes, hydraulic shattering, diapir structures, convolute lamination, load-flame structures, ball-and-pillow structures, loop bedding, and subsidence structures), synsedimentary faults, and seismoturbidites. In addition, mixed-source rudstones, consisting of the Paleozoic carbonate clasts and in situ calcilutite clasts in the lowermost submember of Shahejie 3, appear in the seismites, suggesting an earthquake origin. A complete representative vertical sequence in the lowermost part of the third member found in well ST1H located in the central part of the Shulu Sag shows, from the base to the top: underlying undeformed layers, synsedimentary faults, liquefied carbonate rocks, allogenetic seismoturbidites, and overlying undeformed layers. Seismites are widely distributed around this well and there are multiple sets of stacked seismites separated by undeformed sediment. The nearby NW-trending Taijiazhuang fault whose fault growth index is from 1.1 to 1.8 and the NNE-trending Xinhe fault with a fault growth index of 1.3–1.9 may be the source of the instability to create the seismites. These deformed sedimentary layers are favorable for the accumulation of oil and gas; for example, sedimentary dikes can cut through many layers and serve as conduits for fluid migration. Sedimentary faults and fractures induced by earthquakes can act as oil and gas migration channels or store petroleum products as well. Seismoturbidites and mixed-source rudstones are excellent reservoirs due to their abundant primary or dissolved pores. [ABSTRACT FROM AUTHOR]

Palaeoseismological studies were performed within the Yaloman graben (Gorny Altai). Five Quaternary sections with coseismic deformation structures (seismites) have been recognized in the lower course of the Malyi Yaloman River. Traces of ancient earthquakes are localized at two levels (Late Pleistocene-Holocene). The most likely mechanisms of the seismite formation are brittle failure, liquefaction, and fluidization. The types of coseismic deformations and their sizes suggest that the Yaloman graben was the locus of prehistoric earthquakes with M > 5–7, although modern-day seismic activity consists of smaller-magnitude earthquakes. This should be taken into account in assessing the seismic hazards during construction of gas pipeline to China and tourism infrastructure facilities. [ABSTRACT FROM AUTHOR]

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 a 75 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 45 ka have been inferred. [ABSTRACT FROM AUTHOR]

Shallow lakes along minor structural bends or discontinuities of strike-slip faults are not usually paleoseismological target sites. In the present study, we show that a 2-m-deep, 700-m-long lake that is cross-cut by the North Anatolian Fault contains a reliable paleoseimological record that can be obtained through coring. The North Anatolian Fault is a major strike-slip fault in Turkey, and it last ruptured across the Aşağıtepecik Lake in 1939, with a slip of about 6 m. Seismic lines still show remains of the fault rupture in the form of minor scarps across the lake. Collected short cores show a set of sedimentary sequences. Each sequence is composed of similar organic-rich sedimentary units. The lower unit is dark and fibrous, and is similar to the present sedimentation at the top of the core. The upper unit is disturbed and has anomalous organic matter content, grain size and mineralogy. It is interpreted as an earthquake-induced sedimentary event. The 2.5-m-long AT2007LG core comprises four sequences, and four sedimentary events. Radiogenic 210Pb and 137Cs data obtained previously imply that the shallowest event 1 was triggered by the 1939 M = 7.9 Erzincan earthquake. Radiocarbon dating and correlation to a reference varved record suggest that events 2 and 4 were initiated by the 1668 and 1254 historical earthquakes. Event 3 does not correspond to a large historical earthquake on the North Anatolian Fault.

Various millimetre-, centimetre- and metre-scale soft-sediment deformation structures (SSDS) have been identified in the Upper Ordovician and Lower-Middle Silurian from deep drilling cores in the Tarim Basin (NW China). These structures include liquefied-sand veins, liquefaction-induced breccias, boudinage-like structures, load and diapir- or flame-like structures, dish and mixed-layer structures, hydroplastic convolutions and seismic unconformities. The deformed layers are intercalated by undeformed layers of varying thicknesses that are petrologically and sedimentologically similar to the deformed layers. The SSDS developed in a shelf environment during the early Late Ordovician and formed initially under shear tensile stress conditions, as indicated by boudinage-like structures; during the latest Ordovician, SSDS formed under a com-pressional regime. The SSDS in the Lower-Middle Silurian consist mainly of mixed layers and sand veins; they formed in shoreline and tidal-flat settings with liquefaction features indicating an origin under a compressional stress regime. By Silurian times, the centre of tectonic activity had shifted to the south-eastern part of the basin. The SSDS occur at different depths in wells that are close to the syn-sedimentary Tazhong 1 Fault (TZ1F) and associated reversed-thrust secondary faults. Based on their characteristics, the inferred formation mechanism and the spatial association with faults, the SSDS are interpreted as seismites. The Tazhong 1 fault was a seismogenic fault during the later Ordovician, whereas the reversed-direction secondary faults became active in the Early-Middle Silurian. Multiple palaeo-earthquake records reflect pulses and cyclicity, which supports secondary tectonic activity within the main tectonic movement. The range of SSDS structures reflects different developments of tectonic activity with time for the various tectonic units of the centralbasin. The effects of the strong palaeo-earthquake activity coincide with uplift, fault activity and syn-tectonic sedimentation in the study area during the Late Ordovician to Middle Silurian. [ABSTRACT FROM AUTHOR]

This study aims for the characterization of the geological setting of 300MW Baspa II, India's largest private hydroelectric facility which was built on top of a relict rock avalanche dammed palaeo-lake (Baspa Valley, NW Himalaya). Geologically, the hydroelectric installation is located in the Higher Himalayan Crystalline, just above the active Karcham Normal Fault, which is reactivating the Early Miocene Main Central Thrust, one of the principal Himalayan faults. The area is seismically active and mass-movements are common. At ca. 8200yr BP the Baspa River was blocked behind a 142×106 m3 rock avalanche dam which created a ca. 260m deep palaeo-lake. The whole palaeo-lake was completely filled with sediments in about 3100years, making the Sangla palaeo-lake to a very rare example of a mass-movement dam with very long duration. The hydroelectric installation was built with its intake situated directly on top of the mass-movement dammed palaeo-lake of Sangla, utilizing the convex knick point in the river profile to increase the head for Baspa II for ca. 125m, compared to the reconstructed longitudinal profile of the river prior to the mass-movement, which amounts for about 18% of its design head. At least 5 levels of soft-sediment deformation have been recorded in the exposed part of the lacustrine sediments of Sangla palaeo-lake, including brecciated laminae, overturned laminae, folds, faults and deformation bands, separated by undeformed deposits. They are interpreted as seismites, indicating at least 5 earthquakes within 2495±297years strong enough to cause liquefaction. These observations extend the local seismicity record considerably into the past and indicate more and possibly stronger seismic events than might be expected from the instrumental measurements. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the study is to detect deformations in the soft sediments in a tectonically active area (the Armenian Highland) and to examine the significance of the deformations as paleoseismicity indicators. Deformations in the form of pillows, pockets, sharp waves, and ovoids are exposed in the Sevan basin, within interbedded shallow lacustrine, beach, and fluvial sediments. Also, broken beds and low-amplitude thrusts are observed. Eight field criteria for assigning soft-sediment deformations to paleoseismic triggering provide strong evidence for the seismic origin of the deformations. According to the local relative stratigraphic scale, the Sevan seismites are of Pleistocene–Holocene age. [Copyright &y& Elsevier]

Abstract : The lower Katun’ area has a complex neotectonic framework, with the largest fault zone of Katun’ consisting of several en-echelon graben segments. Late Pleistocene sediments that fill the Katun’ Fault bear signature of earthquake-induced soft-sediment deformation (seismites). Deformation due to seismic triggers can be discriminated from nonseismic one on the basis of special features and be related to prehistoric earthquakes according to a number of criteria. The observed deformation inside and outside burial mounds of the Chultukov Log-1 group may result from an earthquake that occurred in the end of the first millennium BC. Fault scarps in Late Pleistocene sediments, as well as deformed Iron Age tomb patterns, indicate that the Katun’ lower reaches can have experienced past earthquakes of intensity at least 5 or 6 and magnitudes from 4.5 to 6.0. [Copyright &y& Elsevier]

Abstract: Coseismic soft-sediment deformation has been studied by structural and tectononophysical methods in the Selenga Delta area shaken by the devastating M ∼ 7.5 Tsagan earthquake in 1862. Among the documented deformation structures (seismites), clastic dikes are the most reliable paleoseismic indicators. The dikes have their sizes and extent showing proximity to the primary coseismic rupture zone and are closely associated with faults of different hierarchic levels. The Tsagan event occurred under SW–NE extension as motion on a stepped system of normal faults dipping at 300°–350°, ∠45°–75°. The amount of vertical motion measured against a reference layer in a trench reached 2.83 m, and the maximum dip displacement measured in a single fracture was 0.5 m. The earthquake was generated by the Delta Fault that dips at 60° on average to the northwest. The distribution of quantitative parameters of brittle and brittle-plastic deformation has been analyzed along two profiles, and two new parameters were introduced: indices of mean intensity (I) of clastic dikes and microdikes; the new parameters were calculated by specially developed equations. Summation of significant peaks in all parameters (SUMspp) allowed contouring the zone of most intense soft-sediment deformation near Dubinino Village. Deformation mostly propagated in the NE–SW and N–S directions. The location of the 1862 Tsagan earthquake at 52.35° N and 106.67° E was inferred from the SUMspp value taking into account the dip of the causative fault plane and the average origin depth of earthquakes in the Baikal rift. The approach we used is applicable to locating preinstrumental events. The recurrence of large earthquakes in the area of Proval Bay (Lake Baikal) has been estimated to be 1120–1230 years proceeding from alternating deformed and undeformed sediments in the sections, their thicknesses and deposition rates according to radiocarbon dating. The seismic activity has been associated with the same fault which can generate M ≥ 7 events. [Copyright &y& Elsevier]

Abstract: Syn-sedimentary deformation structures (SSDs) can indicate disturbance caused by autogenic or allogenic processes affecting the depositional system. Such structures are prolific in the Proterozoic shallow marine sediments of Kaladgi Basin, especially in the basal part of the succession (Lokapur Subgroup), in both clastics and carbonates. Widespread distribution, lateral traceability of the deformed horizons across several hundreds of meters, their occurrence between undeformed beds and proximity to NW–SE to E–W trending faults and shears are used to attribute a seismic origin to some of these SSDs. Release of accumulated stresses in the basin floor undergoing extension caused the episodic seismic activity producing the seismites. These “seismites” record the syn-sedimentary tectonism that controlled facies distribution patterns in the Mesoproterozoic Bagalkot Group in conjunction with sea-level fluctuations. On one hand, this is a contribution towards recognition of seismic events during the Mesoproterozoic, a period from which few seismites have been recorded. On the other hand, recognizing that the crustal processes that operated in brittle regimes during the creation of this extensional supracrustal basin around 1800Ma were comparable to those operating in present day extensional systems opens a window of understanding how the Proterozoic platform basins hosting thick shallow marine sequences evolved. [Copyright &y& Elsevier]

Abstract: Soft-sediment deformation structures have been analyzed at six sites of the Kathmandu valley. Microgranulometric study reveals that silty levels (60 to 80% silt) favor the development of soft-sediment deformation structures, while sandy levels (60 to 80% sand) are passively deformed. Nonetheless well sorted sand levels (more than 80% sand) generate over-fluid pressure during compaction if located beneath a silty cap, leading to fluidization and dike development. 3-D geometry of seismites indicates a very strong horizontal shearing during their development. Using a physical approach based on soil liquefaction during horizontal acceleration, we show that the fluidization zone progressively grows down-section during the shaking, but does not exactly begin at the surface. The comparison of bed-thickness and strength/depth evolution indicates three cases: i) no soft-sediment deformation occurs for thin (few centimeters) silty beds; ii) the thickness of soft-sediment deformation above sandy beds is controlled by the lithological contrast; iii) the thickness of soft-sediment deformation depends on the shaking intensity for very thick silty beds. These 3 cases are evidenced in the Kathmandu basin. We use the 30cm-thick soft-sediment deformation level formed during the 1833 earthquake as a reference: the 1833 earthquake rupture zone extended very close to Kathmandu, inducing there MMI IX–X damages. A 90cm-thick sediment deformation has therefore to be induced by an event greater than MMI X. From a compilation of paleo and historic seismology studies, it is found that the great (M~8.1) historical earthquakes are not characteristic of the greatest earthquakes of Himalaya; hence earthquakes greater than M~8.6 occurred. Kathmandu is located above one of the asperities that laterally limits the extent of mega-earthquake ruptures and two successive catastrophic events already affected Kathmandu, in 1255 located to the west of this asperity and in ~1100 to the east. [Copyright &y& Elsevier]

Abstract: Epicontinental seismicity is currently a subject of intense study by geologists and engineers, particularly relative to triggering mechanisms, epicentral areas, and recurrence intervals. Aside from modern seismic events, much of the evidence for previous events is in the form of soft-sediment deformation, which has often been systematically overlooked or misinterpreted. Carbonates have also been systematically ignored in most attempts to understand soft-sediment deformation. Soft-sediment deformation, however, is not a unique response to seismicity; so how do we know when seismicity is implicated or not? The concurrence of four criteria has been suggested as a way to confirm the likelihood of seismogenic origins for soft-sediment deformation: 1) presence of deformation consistent with a seismogenic origin; 2) deformation that is widespread; 3) deformation that can be temporally or stratigraphically constrained across its distribution; and 4) deformation that is zoned across its distribution, showing systematic increases in frequency, size or intensity toward a likely epicentral area. The greater the concordance of these criteria, the more likely a seismogenic origin is. In order to validate these criteria, we scrutinized two very different examples of epicontinental, carbonate, soft-sediment deformation, which had been called seismites: one from the shallow, open-marine, Upper Ordovician Lexington Limestone of central Kentucky, USA, and another from the peritidal, dolomitic, Mesoproterozoic, Wumishan Formation of northeast-central China. Concurrence of criteria for Lexington soft-sediment deformation readily supports the case for a seismogenic origin, whereas for Wumishan deformation, too few criteria were satisfied to implicate seismicity. Nonetheless, after exclusion of all other possibilities for Wumishan deformation, seismicity stood out as the only likely cause. Although concurrence of the four noted criteria in soft-sediment deformation almost certainly does indicate a seismogenic origin, the co-occurrence of criteria is rare and wholly dependent on past depositional environments and modern occurrence. Hence, the four criteria cannot be used as universal seismogenic indicators, and in the absence of such indicators, we must continue to rely upon the integration of tectonic, structural, and paleoenvironmental clues for substitute corroboration. [Copyright &y& Elsevier]

Abstract: Well-exposed soft-sediment deformation (SSD) structures occur in Tecopa paleolake beds largely composed of ash from the Bishop (760kyr) and the Lava Creek (640kyr) ultra-plinian eruptions. In both cases the SSD structures affected volcaniclastic deposits concentrated by overland flow from the surrounding topography into the lower slope and lake environments. Re-sedimentation of ash produced alternations of volcaniclastic layers with different grain sizes and ash content that allowed for reverse density gradients, which favoured liquefaction and deformation. In the Tecopa Basin, extensive outcrops show these deformed strata continuing laterally for hundreds of metres, along with three-dimensional exposures. This study illustrates the 3-D complexity of soft-sediment deformation including some novel morphologic features. Of particular interest were examples of superposed deformed beds that laterally change into one single deformed horizon. Heterogeneities in ash concentration, grain-size, and water content produced contrasting permeabilities that were barriers to liquefaction and soft-sediment deformation. The probable causes for liquefaction were Middle Pleistocene paleo-earthquakes. There are several active faults in the region with enough seismic potential to produce moderate to large earthquakes. The fact that a single deformed deposit laterally merges into multiple superposed deformed beds indicates that multilayer liquefaction could be produced by a single shaking event. In these cases, SSD layers are insufficient and unreliable indicators of paleo-seismic recurrence intervals. [Copyright &y& Elsevier]

Abstract: The detailed study of four deformed intervals from the Holocene fluvio-lacustrine deposits of the Santa Fe–Sopetrán Basin in northern Colombia shows 17 types of soft-sediment deformation (SSD) structures. Evidence indicates that seismic activity was responsible for the SSD structures, a conclusion reached after considering the environmental conditions at the time of sediment deposition and shortly after, and the detailed analysis of the driving force systems. Other triggers (i.e. overloading and rapid sedimentation), however, are not discarded. Intervals showing SSD structures occurred at centennial frequencies and apparently resulted from Mw 6–7 earthquakes. The Holocene age of these major shaking events should be seriously considered when evaluating the seismic hazard and risk for the middle Cauca Valley and the nearby city of Medellín with 3million inhabitants. [Copyright &y& Elsevier]

The Raniganj basin in the Damodar valley of eastern India is located within the riftogenic Gondwana Master-Basin. The fluvio-lacustrine deposits of the Lower Triassic Panchet formation of the Damodar valley in the study area preserve various soft-sediment deformation structures such as slump folds, convolute laminae, flame structures, dish-and-pillar structures, sandstone dykes, pseudonodules and syn-sedimentary faults. Although such soft-sediment deformation structures maybe formed by various processes, in the present area the association of these structures, their relation to the adjacent sedimentary rocks and the tectonic and depositional setting of the formation suggest that these structures are seismogenic. Movements along the basin margin and the intra-basinal faults and resultant seismicity with moderate magnitude (2-5 on Richter scale) are thought to have been responsible for the soft-sediment deformations. [ABSTRACT FROM AUTHOR]

Abstract: New data on soft-sediment deformation in Late Pleistocene and Holocene deposits of the northwestern Kola Peninsula (Pechenga River valley) are reported and analyzed in terms of paleoseismicity implications. Soft-sediment deformation is assigned to paleoseismic triggers on the basis of special criteria. One sedimentary section in the Pechenga valley bears signature of several seismic events at the Late Pleistocene–Holocene boundary, constrained by radiocarbon dates. According to the morphology, sizes, and types of seismites, the earthquakes had an MSK-64 intensity at least VI–VII. The observed earthquake-induced deformation may be associated with tectonic subsidence of the Pechenga valley block. [Copyright &y& Elsevier]

The Haiyuan fault is a major active left-lateral fault along the northeast edge of the Tibet-Qinghai Plateau. Studying this fault is important in understanding current deformation of the plateau and the mechanics of continental deformation in general. Previous studies have mostly focused on the slip rate of the fault. Paleoseismic investigations on the fault are sparse, and have been targeted mostly at the stretch of the fault that ruptured in the 1920 M ∼ 8.6 earthquake in Ningxia Province. To investigate the millennial seismic history of the western Haiyuan fault, we opened two trenches in a small pull-apart basin near Songshan, in Gansu Province. The excavation exposes sedimentary layers of alternating colors: dark brown silty to clayey deposit and light yellowish brown layers of coarser-grained sandy deposit. The main fault zone is readily recognizable by the disruption and tilting of the layers. Six paleoseismic events are identified and named SS1 through SS6, from youngest to oldest. Charcoal is abundant, yet generally tiny in the shallowest parts of the trench exposures. Thirteen samples were dated to constrain the ages of paleoseismic events. All six events have occurred during the past 3500-3900 years. The horizontal offsets associated with these events are poorly known. However, events SS3 to SS6 appear to be large ones, judging from comparison of vertical separations and widths of fault zones. The youngest event SS1 instead seems to be a minor one, probably the 1990 Mw 5.8 earthquake. Thus, four large events in 3500-3900 years would imply a recurrence interval of about 1000 years. Three events SS2 to SS4 prior to 1990 occurred sometime during 1440-1640 A.D., shortly after 890-1000 A.D. and 0-410 A.D., respectively. We tentatively associate them with the 1514 AD., 1092 A.D., and 143 or 374 A.D. historical earthquakes. Taking 10 ± 2 m of slip for large events (SS3 and SS4), comparable to the 1920 M > 8 Haiyuan earthquake, their occurrence times would be consistent with the long-term 12 ± 4 mm/yr estimate of Lasserre et al. (1999). However, a more realistic evaluation of slip rate and its possible change with time requires a more rigorous determination of coseismic slip amounts of past earthquakes. [ABSTRACT FROM AUTHOR]

Abstract: A detailed study of the syndepositional Masada Fault Zone (MFZ) provides an example for fundamental characteristics of earthquakes, such as long term temporal clustering, repeated faulting on the same planes for a limited time of the order of a few thousands of years, and the formation of subaqueous breccia layers interpreted as seismites. The MFZ was studied in outcrops of 70–15 ka Lake Lisan sediments. Detailed columnar sections on both sides of well-exposed faults show that each individual fault exhibits a cluster, up to 4 ky long, with 3–5 slip events on the same plane. Each slip event is associated with the formation of widespread layers exhibiting soft sediment deformation, which are interpreted to be seismite layers. The uppermost part of the Lisan section, about 5 m, is not faulted, hence the last cluster of slip events ended about 25 ky ago. The clusters of activity of individual faults coalesce to form larger clusters. These are evident in the distribution of seismite layers throughout the entire Lisan section which shows earthquake clustering during periods of ∼10 ky. The clusters are separated by relatively quiescent periods of comparable duration. [Copyright &y& Elsevier]

Several studies have cited soft-sediment deformation as evidence of fault reactivation and paleoseismicity in intraplate coastal settings. However, a consensus has not been reached on the extent of paleoseismic activity in several regions and the link with continental-scale faults. This research aims to determine the origin of the deformation in soft-sediments, both in the Neogene Barreiras Formation and in Pleistocene sediments of the Sergipe-Alagoas Basin, on the continental margin of northeastern Brazil. The region shows a historical record since 1808 of earthquakes with maximum modified Mercalli intensity of VII and a 40-year instrumental record of events with maximum body-wave magnitude (mb) of 5.2. The brevity of these records leads to large uncertainties in estimates of fault slip rate, recurrence, and seismic hazard. Geologic studies of seismically induced soft-sediment deformation structures and their relationship to seismically active faults offer the opportunity to reduce these uncertainties. We present detailed descriptions of the deformation structures with emphasis on morphology, ductile or brittle character, size, and distribution of the features. In addition, we integrate geologic data with seismic reflection data, thus allowing for correlation between the normal faults at the seismic scale and the soft-sediment deformation structures at the outcrop scale. Faults associated with seismites at the outcrop scale exhibit the same strike/dip and kinematics and are spatially related to the major faults identified at the seismic-section scale. Regarding ductile features, the most remarkable are convoluted folds associated with a deformed muddy layer, giant sinking structures, and complex folds. Concerning brittle structures, the most striking are clastic dikes, mixed layers, autoclastic breccias, and fault breccias. The alternating records in the Neogene sediments indicate clustered seismic activity, combined with tectonic quiescence periods. In Pleistocene sediments, the size, frequency, lateral continuity, and spatial distribution of tens of kilometers of the deformation structures indicate a period of frequent earthquakes with body-wave magnitudes equal to or greater than 6. The recognition of seismic activity and brittle reactivation of preexisting faults during the Neogene-Quaternary has far-reaching implications for seismic hazards in intraplate settings. • We have identified brittle and ductile soft sediment deformation. • The paleoseismicity is higher than the short instrumental and historical record of seismicity. • Reactivation of Cretaceous faults affected Miocene and Pleistocene sediments. • Seismic profiles corroborate with field data interpretation. • The Late Pleistocene was submitted to strong seismic shocks. [ABSTRACT FROM AUTHOR]

• Seismites in Quaternary sediments are first described in the Hangjiahu Coastal plain. • Seismites indicate three episodes of seismicity during the Late Pleistocene. • Paleoseismicity represent the syn-depositional tectonic activity of the Taihu block. Drilling cores from the Hangjiahu Coastal plain in the southwestern corner of the Southern Yangtze River deltaic plain, East China, contain a variety of soft-sediment deformation structures in the Late Pleistocene lacustrine and tidal sediments. They include load-flame structures, ball-and-pillow structures, diapir structures, liquefied sand veins, liquefied breccias, syn-sedimentary fault, seismo-cracks and brittle breccias. Sedimentary facies assessment of host deposits and development features rule out an exogenic origin of the soft-sediment deformation structures, such as gravity-flow, storm activity, wave action or flood. These soft-sediment deformation structures in the study area are interpreted as seismites, their spatial distribution suggest that the earthquakes were sourced from the intersection of the Majin-Wuzhen Fault and the Huzhou-Jiashan Fault. Seismites recognized in cores indicate three episodes of short and sudden seismicity (magnitude > 5), which are interpreted as a response to syn-depositional tectonic activity and differential subsidence of the Taihu block during the Late Pleistocene period. Systematic study of spatial and temporal distribution of these seismites improves the understanding of the tectonic context and evolutionary history of sedimentary basement. [ABSTRACT FROM AUTHOR]