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Due to continued continental convergence of Indian–Eurasian plates, the Himalayan region witnessed several high-magnitude earthquakes and is prone to major seismic events in future as well. Most of the countries with seismically active faults examine paleo seismic data in site specific as well as regional seismic hazard analyses. Hence, it is of great concern to find evidence for prehistoric earthquakes following the morphotectonic route and establish the recurrence intervals of potential earthquakes by characterising and dating large prehistoric events. The present study discusses the paleo seismicity and induced deformational features in the Trans-Yamuna region of the outer Northwest Himalaya by interpreting soft sediment deformation and paleo-liquefaction features. We targeted two sites along the Trans-Yamuna active fault system, which are located in the Sirmurital and Bharli villages; both of these locations are close to Doon Valley along the Main Boundary Thrust. Temporal distribution of paleo-liquefaction features evident major seismic events likely to occur during 16th and 19th centuries, which clearly indicates reactivation of faults in this hinterland region that could experience major rupture during the recurrence of large magnitude earthquake and therefore, constructional activities are a matter of great concern to design structures accordingly. [ABSTRACT FROM AUTHOR]

A quarter of a century ago, during cartographic works using then-known field methods for measuring structural features, on the boundary of the Sudetic and Fore-Sudetic blocks, new phenomena were recognised; these were interpreted to be tectonic in nature and the result of left-lateral strike-slip movement in the subsurface. Grabens, half-grabens, shear zones and seismites in the gold-bearing sands and gravels that form the slopes of the valley of the River Kaczawa, are estimated to be of Pliocene and early Pleistocene age, having been interpreted as deposits of the pre-Kaczawa alluvial fan system. The natural exposures documented 25 years age have now all disappeared. In 2022, these levels became exposed again as a result of renewed gravel exploitation and phenomena described in the past reappeared. Field measurements were made again, this time using modern data-recording techniques, such as photogrammetry and terrestrial laser scanning. This work has enabled a comparison of field measurement methods with those obtained from the point clouds data. The results were found to be highly consistent. At the same time, precise reconstructions of the structures and their connection to the geodetic reference system make it possible to supplement previous geokinematic interpretations for this segment of the Sudetic Marginal Fault Zone (SMFZ). A formerly postulated left-lateral strike-slip regime in this zone was confirmed during the period of formation of the pre-Kaczawa alluvial fan deposits, but also probable is a kinematic inversion that must have occurred during, or just after, the early Pleistocene. [ABSTRACT FROM AUTHOR]

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]

This study highlights signatures of seismic activity along the Moradabad Fault (a transverse basement fault) in the upper Ganga plain. Soft-sediment deformation structures have been identified at different locations around the Moradabad Fault (MF) zone and analyzed from a morphological perspective. The deformational structures include deformed cross-beddings, sand volcanoes, water-escape structures, micro-faults, and plastic intrusions. The mechanism of deformation is related to liquefaction and/or fluidization processes. The presence of seismites and epicenters of recent earthquakes in the Moradabad Fault zone irrefutably associates the seismic activity in the Ganga plain with the basement fault activation. Furthermore, subsurface GPR data, surface geomorphic evidence such as channel offset, stream convergence, initiation of new channels, and different stages of river terrace development in the upthrown and downthrown blocks of the fault suggests the active nature of the Moradabad fault. [ABSTRACT FROM AUTHOR]

A comparative analysis of the morphological features of horizons affected by paleoearthquakes revealed significant difference of seismites from lithologically different deposits. Powerful earthquakes determine not only the destruction of the sedimentary structure of near-surface deposits and their chaotic mixing, but also actively affect the underlying layers to a depth of several tens of meters; since the degree of diagenetic lithification of rocks in different horizons varies with depth, the nature of their seismogenic transformations also changes. It was found that major seismic events were associated with the time intervals of tectonic and paleogeographic restructuring of sedimentation basins, which consisted in the intensification of the basin floor subsidence and changes in the composition of sediments accumulated in the paleobasin. A special type of seismites was formed during the impact of earthquakes on siliceous deposits, which have been spanned by the diagenetic redistribution of authigenic mineral matter in a gel state. [ABSTRACT FROM AUTHOR]

Extraterrestrial cratering was a critical component in the evolution of the early Earth, but discovery of very ancient and deeply exhumed impact structures remains elusive, as identification tools are in short supply. The recognition of such structures is hindered by post-cratering geological processes, whereby impact-induced features common in younger, upper-crustal craters may be lost. In this study, we make a detailed analysis of planar microstructures in zircons from four large, confirmed impact structures (Manicouagan, Rochechouart, Sudbury, Vredefort) preserved at different crustal levels, from two previously described non-impact seismites in SW Norway and northern Italy, and from the 3.0 Ga Maniitsoq structure in West Greenland. A total of ~3400 zircon grains were studied using exterior and interior scanning and transmission electron microscopy. We show for the first time that shocked zircons contain two successive, principally different types of planar microstructures, only one of which is diagnostic of impact. Closely spaced, contiguous microplanes (CP) are formed first, presumably by the shock wave. In Manicouagan and Rochechouart zircons the exterior CPs have ultrathin interior counterparts of straight dislocation arrays, as identified in Manicouagan zircon using transmission electron microscopy. They have the same close spacing and orientations as the exterior CPs and are abundantly decorated with tiny pores down to less than 50 nm across. These interior CPs are identical to shock-induced decorated, partly annealed amorphous planar microstructures in quartz (planar deformation features, PDFs) and are interpreted as such. The second type is open planar fractures (PF). They are widely and irregularly spaced and texturally younger than the CPs. They re-use and displace the CP orientations, which they cut in stepwise fashion. We interpret these PFs as formed by impact-induced seismic shaking in the wake of the shock wave. We confirm two previous reports of isolated planar fractures in zircons from non-impact seismites, showing that PFs per se are not impact-diagnostic. There are no CPs in any of these zircons. Zircons from different parts of the Maniitsoq structure contain CPs in various states of preservation besides PFs, corroborating that this very large and very deeply exhumed structure resulted from an extraterrestrial impact. [ABSTRACT FROM AUTHOR]

Rounded argillite clasts within the lower Gowganda Formation of the Huronian Supergroup near Whitefish Falls, Ontario, have been historically mapped as Sudbury Breccia, implying that their formation was initiated by the Sudbury meteorite impact event. Alternative genetic models proposed to explain the breccia at Whitefish Falls include formation through intrusion of diabase into wet sediment accompanied by soft-sediment deformation events. Outcrops in the Whitefish Falls area contain clear evidence for early post-depositional fracturing: flow of argillites into brittle fractured sandstones. Linking these geological processes suggests that the formation of the breccia at Whitefish Falls was generated by faulting of the Huronian sedimentary basin during the sedimentation of the Gowganda argillites. Using a GIS approach to compare the distribution of known breccia bodies with mapped lithology and structure, it is apparent that the term Sudbury Breccia has been applied to two types of breccias. First, true Sudbury Breccia, which is characterised by rounded heterogeneous clasts in an aphanitic matrix, is only found in proximity to the Sudbury Impact crater. The distribution of the second, primarily sediment derived, type of breccia, as seen at Whitefish Falls, is strongly associated with mapped faults and regional-scale basement discontinuities, as defined by gravity and magnetic data. Since this type of breccia is present throughout the entire Huronian sedimentary sequence, the term "Huronian Breccia" is more appropriate. This breccia is not the result of a single geological event but rather episodes of fault activity, as the geometry of the Huronian basin evolved over time. [ABSTRACT FROM AUTHOR]

Abstract The Dead Sea seismites comprise the worlds longest record of earthquakes. The seismites appear as deformed layers enclosed between undeformed layers of alternating millimetre‐thick laminae with annual pairs of winter detritus and summer evaporitic aragonite. Understanding the physical conditions that govern their formation will promote the recovery of the causative earthquake properties from the deformation character. The first step towards this goal is understanding the microscopic structure of the seismites. To this end, scanning electron microscope images of the Dead Sea Basin sediments were analysed to extract their pore and grain sizes. The implementation of image processing techniques to determine the microscopic‐scale physical properties of the deformed and undeformed layers are in general agreement with results from classical labour‐intensive instruments. However, the image processing analyses provide more detailed unbiased information. A MATLAB‐based code has been developed as a ready‐to‐use package, which can be easily implemented on any other occurrence of soft sediment outcrops to analyse sediment microscopic‐scale physical properties from scanning electron microscope images.

The Hamersley Group in the Hamersley Basin, Western Australia, contains major deposits of banded iron formation of Neoarchean–Paleoproterozoic age (2629–2449 Ma). The 2450 Ma Weeli Wolli Formation near the top of the group includes banded iron formation with microbands (≤0.05–0.5 mm to rarely 1 mm thick) of chert and iron oxide lamina couplets that display distinctive cycles. Some adjacent, thin microbands have merged with compaction and the diagenetic removal of chert laminae, and maximum counts of cycle period by different studies is preferred, suggesting a period of ∼28 ± 2 microbands. Associated cyclic iron formation shows soft-sediment plastic deformation and brittle fracturing. Rare earth element geochemistry indicates that much of the iron in late Archean–early Paleoproterozoic banded iron formations was derived from submarine hydrothermal systems. Monitoring of hydrothermal vents on mid-ocean ridges and seamounts has identified tidal modulation of the discharge, temperature and dispersal of deep-sea hydrothermal plumes principally by semidiurnal variations in tidal loading and earth tides. Microearthquake swarms are associated with deep-sea hydrothermal systems at the crests of mid-ocean ridges, and tidal triggering of microearthquake activity is indicated for a hydrothermal system on the East Pacific Rise. The microband cycles in the Weeli Wolli Formation are interpreted as tidalites, comprising ∼28 ± 2 semidiurnal microbands per lunar (synodic) fortnightly cycle, related to the tidally modulated activity of a submarine hydrothermal system. The associated plastically deformed and brittle-fractured sediments are viewed as seismites resulting from microearthquakes also related to the hydrothermal system. The Weeli Wolli microband cycles and seismites may represent a rarely identified instance of iron-formation deposition near a submarine hydrothermal system. Submarine hydrothermal venting was a major source of iron in late Archean–early Paleoproterozoic banded iron formations. Semidiurnal variations in tidal loading and earth tides commonly modulate present-day deep-sea hydrothermal activity, and microearthquake swarms are associated with deep-sea hydrothermal systems. Early Paleoproterozoic banded iron formation from the Hamersley Basin displays cycles with an estimated period of ∼28 ± 2 microbands and associated plastic deformation and brittle fracturing. The microband cycles are interpreted as tidalites comprising ∼28 ± 2 semidiurnal increments grouped in fortnightly cycles at a tidally modulated submarine hydrothermal system, and the deformed sediments as seismites caused by related microearthquake activity. [ABSTRACT FROM AUTHOR]

A pre-rift Upper Cretaceous succession records evidence of a localized liquefaction at the eastern side of the Gulf of Suez rift, Egypt. Structurally controlled clastic intrusions, slump-like folds and megabreccia are the common liquefaction-induced structures. The sandstone dykes taper upward with no exposed feeder, and are oriented parallel to and along rift-related conjugate normal faults. The slumps are localized, spatially related to rift-related faults, and preserved within mudstone-dominated layers with more competent sandy shale interbeds. The megabreccias are chaotic, and stretched sporadically along the footwall of a rift-related fault. Meteorite impact, explosive volcanicity, and storm wave actions are excluded as trigger mechanisms. Recent and paleo-earthquake records show that the Neogene Gulf of Suez rift is a seismically active belt with a southward increase in seismic activity. Tectonic-related seismic activity is suggested as a plausible trigger for the liquefaction. Movement along rift-related faults during Oligo-Miocene times might have triggered earthquakes that produced the paleo-seismites. [ABSTRACT FROM AUTHOR]

A continuous succession of marine and marginal-marine sediments of Rhaetian (Late Triassic) and Hettangian (Early Jurassic) age is present in the Larne Basin in Northern Ireland. These strata cover a period in Earth's history that included the emplacement of the Central Atlantic Magmatic Province (CAMP), the End Triassic Mass extinction (ETE), the Triassic–Jurassic Boundary (TJB), and major perturbations in the global carbon cycle. The Waterloo Bay section in the Larne Basin offers a well exposed sedimentary succession that spans this interval, and it has previously been proposed as a candidate GSSP for the base of the Jurassic System. A high-resolution δ13C org and organic carbon record for this locality is presented here, with these new data tied to previous stratigraphic descriptions, ammonite biostratigraphy, atmospheric carbon dioxide concentration (p CO 2) estimates, and nearby borehole sections that do not suffer from the thermal alteration that has affected the Waterloo Bay section. Several new exposures, unaffected by thermal metamorphism, are described that could provide future palynological and micropalaentological studies across this important boundary interval. Correlation is established between the well-studied sections in north Somerset and the likely position of the TJB in the Larne Basin, and records of soft sediment deformation, synsedimentary fault movement, relative sea-level change and their likely causes are discussed. [ABSTRACT FROM AUTHOR]

To promote oil and gas exploration of the Carboniferous formation in the Shibei sag, the northeastern margin of Junggar Basin, recently drilled rocks from Well ZB6 with typical seismics were characterized. Through systematic core observation, the identification marks of seismites were described, a vertical sequence of seismites was established, and its oil and gas geological significance was analyzed. The results show that the seismites have typical identification marks, such as soft-sediment deformation structures (including five typical marks: liquefied stone vein, liquefied crinkled deformation structure, ball–pillow structure, flame structure and load cast, water release structure and liquefied breccia), brittle fracture structures (including three typical marks: seismic fractures, synsedimentary microfractures and seismic fracture rock) and special rock types, such as seismic grain-supported conglomerates. The stratigraphic succession reconstructed in Well ZB6 was characterized, from base to top, by (1) a basal non-seismic interval; (2) a seismic interval made up of a grain-supported conglomerate level, brittle fracture level, soft-sediment deformation level; and (3) a non-seismic interval. The discovery of seismites has oil and gas geological significance for improving reservoir performance and forming favorable source–reservoir–cap assemblages. The research describes the new reservoir genetic type and exploration direction of the Carboniferous formation in the Shibei sag (China), which has important guiding significance for the next step of oil and gas exploration. [ABSTRACT FROM AUTHOR]

Soft-sediment deformation structures have been identified in glaciolacustrine deposits of the terrace complexes of Imandra Lake (Kola Region, northeastern part of the Fennoscandian Shield). According to the paleoseismological criteria, we found that these deformation structures were induced by strong earthquakes. These earthquakes led to the occurrence of secondary deformations of various morphology and sizes in the sandy sediments, forming a single complex consisting of intensely deformed and destructed deposits and associated clastic dikes and cracks. Among the plastic deformations, the phenomena of liquefaction, boudinage structures, flame structures, irregular convolute stratifications, diapir-like structures and synsedimentary folds are developed. Cracks, micro-fractures, and dykes predominate among brittle deformations. The spatial and stratigraphic distributions of soft-sediment deformation structures were used to infer about the activation of faults during the Late Glacial and Postglacial period of the sublatitudinal and northwestern strike directions that limit the different-scale blocks of the Earth's crust. According to radiocarbon analysis data and paleogeographic reconstructions, the formation of soft-sediment deformations took place at the end of the Younger Dryas and the beginning of the Preboreal period between 12 900–11 500 cal. a BP, and later, in the Preboreal period and beginning of the Boreal period between 11 500–9900 cal. a BP. It was this period that was accompanied by increased seismic activity not only in the Kola region, but also in the whole of Fennoscandia. [ABSTRACT FROM AUTHOR]

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The Dead Sea seismites comprise the worlds longest record of earthquakes. The seismites appear as deformed layers enclosed between undeformed layers of alternating millimetre‐thick laminae with annual pairs of winter detritus and summer evaporitic aragonite. Understanding the physical conditions that govern their formation will promote the recovery of the causative earthquake properties from the deformation character. The first step towards this goal is understanding the microscopic structure of the seismites. To this end, scanning electron microscope images of the Dead Sea Basin sediments were analysed to extract their pore and grain sizes. The implementation of image processing techniques to determine the microscopic‐scale physical properties of the deformed and undeformed layers are in general agreement with results from classical labour‐intensive instruments. However, the image processing analyses provide more detailed unbiased information. A MATLAB‐based code has been developed as a ready‐to‐use package, which can be easily implemented on any other occurrence of soft sediment outcrops to analyse sediment microscopic‐scale physical properties from scanning electron microscope images. [ABSTRACT FROM AUTHOR]

Tectonic events caused by paleoearthquakes are reflected in sediments. Outcrops and cores from the Chang-7 Member of the Late Triassic Yanchang Formation, Ordos Basin in Northern China, yield a wide variety of soft-sediment deformation structures (SSDSs), many of which are laterally extensive for more than 150 km. They include various types of folds, soft-sediment liquefaction flow deformation (liquefied sand dyke, liquefied breccia), gravity-driven deformation (load structures, ball-and-pillow structures), hydroplastic deformation (loop bedding, convolute deformation), and brittle deformation (intrastratal and stair-step faults, cracks). In most cases, deformation resulted in hybrid brittle-ductile structures exhibiting lateral variation in deformation style. These occur in delta front to semideep-to-deep lake sands and mudstones (shales). The seismites recognized in outcrops and cores indicate earthquakes with magnitudes (Ms) between 6 and 8, which are interpreted as a response to orogenic events related to the collision of the South China Block (SCB) and North China Block (NCB) during the Late Triassic period. Systematic study of the spatial and temporal distribution of these seismites improves the understanding of the tectonic context and evolutionary history of sedimentary basements. This study can provide a new perspective on the evolution of tectonic activities in the basin. [ABSTRACT FROM AUTHOR]

A complex of dislocations is described (extended gently dipping faults with a displacement of up to 1 m, dipping towards the center of the lens, steep faults with displacements of 5–20 cm), liquefaction structures (angular pseudonodules of sands in silts), near fault and near-strike-slip fault folds in the section of a large lens of the Mikulinskiy lacustrine–bog sediments (interbedded silt with a horizon of peat and clayey gyttja) of the aseismic region of the Russian Plate (Klin–Dmitrov ridge) in order to compare them with similar structures of the Baltic Shield, the seismogenicity of which is being discussed. It has been shown that the sequence was not subjected to periglacial phenomena such as glaciotectonics, glaciokarst, cryogenic deformations, the presence of which and pseudomorphism along polygonal-veined ice was noted only in the roof of the Mikulinskiy interglacial complex. A model is proposed for the formation of dislocations as a result of slumping of a silt layer with uneven subsidence of the underlying layers of peat sediments, which have been strongly compacted during lithogenesis, which explains the features of the kinematics of faults. The results showed that the dislocations of the Mikulinsky complexes of the Dmitrov quarry do not fundamentally differ from similar structures of the Baltic Shield, which confirms their lithogenic or exogenic (rather than seismotectonic) genesis in both regions. The differences in the dislocation complexes of the two regions are in the different sequence of formation of liquefaction and faults structures: in the Dmitrov section, they were formed synchronously, in the sections of the Baltic Shield, asynchronously. [ABSTRACT FROM AUTHOR]

Late Pleistocene glaciolacustrine sediments in the northern part of Estonia show a wide spectrum of ductile and brittle deformation structures like: (1) injection structures, dish structures, load casts, pseudonodules, ball-and-pillow structures, flame structures and fragments of broken-up sandy laminae all occurring in three internally deformed layers separated by undeformed layers, (2) large-scale upright gentle folds of outcrop size, (3) faults and fractures, and (4) water-escape structures (hydrofractures). We investigate the potential trigger mechanisms for the development of these deformation structures, their relationship in space and time as well as the lithological and geometrical features of soft-sediment deformation structures necessary to recognise deformation mechanisms. Based on comprehensive geological and numerical investigations, we link their origin to two major processes: (1) glacial rebound of Earth's crust causing earthquakes and (2) proglacial and submarginal glaciotectonic processes related to local oscillation of the ice-sheet front. We suggest criteria which allow us to recognise these two trigger mechanisms and propose a new proxy for reconstructing glacigenic processes and environments based on recognised soft-sediment deformation structures and their interrelationships. Our findings also highlight the significance of water saturation levels in glacigenic sediments and their impact on deformation processes. Furthermore, we introduce new types of water-escape structures that develop in proglacial marginal and/or submarginal settings. Our results contribute to a more nuanced interpretation of glacial activity and environmental conditions during the Late Pleistocene period in the study area. • Deformation processes: (1) Glacial rebound causing earthquakes, (2) Proglacial and submarginal glaciotectonic activities. • The significance of water saturation levels in glacigenic sediments and their impact on deformation processes. • Discovery of new types of water-escape structures that develop in proglacial marginal and/or submarginal settings. • First-time modelling of glacially induced Coulomb failure stress changes in Estonia around 14 ka. [ABSTRACT FROM AUTHOR]

Thrust collision zones with low slip rates along the plate boundary are significant areas of stress accumulation and prone to develop more destructive earthquakes with longer recurrence intervals. Such regions are often classified as low seismic risk if they lack continuous records of large earthquakes, such as the eastern Tibetan Plateau before the 2008 Mw 7.9 Wenchuan earthquake. Here, we provide a continuous seismic record in the Longmen Shan thrust fault zone spanning 13,000 years based on detailed investigation of the soft-sediment deformation structures and seismites in the Lixian lacustrine sequence. The recurrence time of large earthquakes (M ≥ 8.1) is 1,200 years, which is significantly shorter than the previous estimate of 2,000–6,000 years. The Maoxian-Wenchuan fault is the main fault that triggered the deformation in the Lixian lacustrine sediments. In addition, earthquake recurrence in the warm period is more frequent than that in the cold period, which should arouse our attention for the seismic study of tectonically active regions.

Liquefaction can cause deformation of unconsolidated sediment, but specific processes involved and the trigger mechanisms often remain obscured. This study describes multiple deformed sediment layers in a succession of lacustrine sand, silt and clay deposited during the Marine Isotope Stage 5d in north‐western Lithuania. The deformation structures (load casts, pseudonodules, ball‐and‐pillow structures, broken‐up laminae and injections) are embedded in ten separate layers of fine‐grained, laterally continuous sediments. Detailed mesoscale sedimentological analyses suggest that each deformation event consisted of numerous successive stages of sediment advection facilitated by liquefaction. Low‐permeability fine‐grained laminae contributed to localized pore‐water pressure build‐up and lowering of sediment strength. Erosional top surfaces that truncate layers with soft‐sediment deformation structures suggest that at least seven deformation events were separated by successive periods of initial erosion and then uninterrupted deposition in the lake. The most likely trigger of the deformation was recurrent palaeoseismic activity possibly linked to a late glacial isostatic adjustment following the Scandinavian Ice Sheet melting after the Saalian glaciation. This study emphasizes the potential role of seismic processes in shaping the sedimentary record of the intraplate region of north‐eastern Europe and contributes to constraining the depth of liquefaction, regardless of the actual trigger mechanism. [ABSTRACT FROM AUTHOR]

A continuous succession of marine and marginal-marine sediments of Rhaetian (Late Triassic) and Hettangian (Early Jurassic) age is present in the Larne Basin in Northern Ireland. These strata cover a period in Earth's history that included the emplacement of the Central Atlantic Magmatic Province (CAMP), the End Triassic Mass extinction (ETE), the Triassic–Jurassic Boundary (TJB), and major perturbations in the global carbon cycle. The Waterloo Bay section in the Larne Basin offers a well exposed sedimentary succession that spans this interval, and it has previously been proposed as a candidate GSSP for the base of the Jurassic System. A high-resolution δ13C org and organic carbon record for this locality is presented here, with these new data tied to previous stratigraphic descriptions, ammonite biostratigraphy, atmospheric carbon dioxide concentration (p CO 2) estimates, and nearby borehole sections that do not suffer from the thermal alteration that has affected the Waterloo Bay section. Several new exposures, unaffected by thermal metamorphism, are described that could provide future palynological and micropalaentological studies across this important boundary interval. Correlation is established between the well-studied sections in north Somerset and the likely position of the TJB in the Larne Basin, and records of soft sediment deformation, synsedimentary fault movement, relative sea-level change and their likely causes are discussed. [ABSTRACT FROM AUTHOR]

The lagoonal and shallow marine sediments of the Penarth Group in the UK span the Triassic–Jurassic boundary. These sediments contain several disturbed levels with soft sediment deformations (SSDs), such as synsedimentary faults, injective domes, recumbent folds and slumps that are recognised in most basins from SW England and South Wales to NW Northern Ireland. Field observations, notably the close link of the SSDs to active faults, attest an earthquake origin of the SSDs. Fluids, faults, overpressure and lithology guided the style of the SSDs and their distribution in the sedimentary sections. Analysis of the directional data relating to SSDs in each disturbed level shows preferred orientations of deformation, which correspond to the local state of stress at the time. We favour a series of earthquakes, rather than a single mega-event as a trigger of the observed features. The active local extensional tectonic context was driven by the opening of the Permo-Triassic basins in Western Europe. The data from the SSDs in the UK suggest the development of a multi-directional, mosaic-style extensional context to occur during this early phase of the break-up of Pangea. Our integrated tectonic/sedimentary study suggests that directional data from faults, injective domes, recumbent folds and slumps preserved in sediments are reliable to reconstruct past seismic activity and basin geodynamics. [ABSTRACT FROM AUTHOR]

The number of gigaton‐sized iceberg‐calving events occurring annually at Greenland glaciers is increasing, part of a larger trend of accelerating mass loss from the Greenland Ice Sheet. Though visual observation of large calving events is rare, ∼60 glacial earthquakes generated by these calving events are currently recorded each year by regional and global seismic stations. An empirical relationship between iceberg size and MCSF, a summary measure of glacial‐earthquake size, was recently demonstrated by Olsen and Nettles (2019), https://doi.org/10.1029/2019JF005054. However, MCSF is known to be sensitive to choices made in modeling the seismic source. We incorporate constraints on the seismic source from laboratory studies of calving and test multiple source time functions using synthetic and observed glacial‐earthquake waveforms. We find that a simple, fixed time function with a shape informed by laboratory results greatly improves estimates of earthquake size. The average ratio of estimated to true peak force values is 1.03 for experiments using our preferred source model, compared with an average of 0.3 for models used in previous studies. We find that maximum‐force values estimated from waveform modeling depend far less on model choices than does MCSF, and therefore prefer maximum force as a measure of glacial‐earthquake size. Using both synthetic and real data, we confirm a correlation between maximum force and iceberg mass. Our results support the possibility of developing useful scaling relationships between seismic observables and physical parameters controlling glacier calving. Plain Language Summary: The Greenland Ice Sheet is losing ice mass. About half of that ice is lost when large icebergs break off, or calve, from the fronts of glaciers into the ocean. Knowing the sizes of these icebergs would be valuable, but iceberg calving is rarely captured on camera. However, the largest icebergs produce seismic signals when they calve, referred to as glacial earthquakes. We investigate the relationship between the size of an iceberg and the magnitude of the glacial earthquake it produces, building new models to describe the forces that generate a glacial earthquake. Previously, most details of the force evolution during iceberg calving were unknown. We use observations from laboratory experiments conducted using a plastic block in a tank of water, built to mimic the glacier‐ocean setting. We find that incorporating information from these laboratory experiments into our seismic model greatly improves estimates of earthquake size. Using our new models, we confirm a correlation between glacial‐earthquake magnitude and iceberg size, and show that our improved estimates are likely to be more realistic. Our results suggest that using seismic information to estimate iceberg size and related quantities is a promising path forward. Key Points: A physics‐based source model for glacial‐earthquake modeling improves recovery of seismic‐magnitude valuesMaximum force is less sensitive to model choices than MCSF and is preferred for describing glacial‐earthquake sizeA rapid force reversal during iceberg calving is the most important feature to capture in a glacial‐earthquake source model [ABSTRACT FROM AUTHOR]

This paper presents results of multidisciplinary geochronologic, paleoseismic, and tectonophysical studies for local structures in the Sloboda tectono-dynamic intersection that is a segment of the junction between major tectonic structures in the East European Platform. These studies were conducted in the area of the Vitebsk–Surazh fault in the central part of the Sloboda intersection. This ancient long-lived discontinuity can be traced using geophysical data in the Precambrian basement. Activation during the platform phase of evolution made the fault penetrate the sedimentary deposits and form a negative flower structure showing signs of tectonic inversion. Since the Late Devonian until the beginning of the Quaternary, the Vitebsk–Surazh northeast striking fault has experienced at least two phases of tectonic activity in a setting of left lateral transpression and right lateral transtension. The Late Pleistocene to Early Holocene evolution of the Vitebsk–Surazh fault gave rise to the formation of graben-like hollows where late glacial and post-glacial lacustrine deposits were accumulated. The Gralevo Quarry shows horizons of seismites, indicators of paleoearthquakes, in the structure of these sediments. The earthquake of the highest intensity has been identified in the seismite structure of Early Holocene varved clay whose radiocarbon age is 9339 ± 36 years. The tectonophysical parameters of this seismic event are in agreement with conditions of normal-oblique deformation with a nearly east–west orientation of the tension axis and a nearly north–south orientation of the compression axis. [ABSTRACT FROM AUTHOR]

Soft-sediment deformation structures (SSDS) were identified in proglacial lacustrine (glaciolacustrine) sediments dated to 25–24 ka in the Buivydžiai outcrop, situated 30 km north of Vilnius in east Lithuania. These sediments accumulated in front of the last Weichselian glaciation maximum. The SSDS originated due to sandy silt liquefaction that disrupted the decimeter-thick silty sand interlayer. A NW-SE trending Buivydžiai fault was mapped in the proximity (8 km) of the Buivydžiai outcrop. The fault is well traced by a dense drilling in the sediments of the preglacial Daumantai Formation in the basal part of the Quaternary cover and attributed to the earliest Pleistocene. Depth difference of the formation along the fault is ~5–8 m; the northern flank is relatively uplifted with respect to the southern flank. The Buivydžiai earthquake was most likely induced by formation of an elastic forebulge flexure of the Earth's crust in front of the ice sheet. The magnitude was evaluated ~M = 6.0–6.5 and was most likely of shallow hypocenter depth. Furthermore, the Bystritsa (Belarus) earthquake of magnitude M = 3.5–4.0 was registered in December 1908 to the east (12 km) of the Buivydžiai outcrop along the Buivydžiai fault, which points to recurrent seismic activity of this fault. [ABSTRACT FROM AUTHOR]

In order to clarify the genesis of liquefaction folds (convolutions) developed at lithological boundaries in lacustrine sediments, such structures in three regions were compared. Folds in each region differ in morphology, composition of sediments, and the vertical gradient of their density and viscosity upon deformation. It is proposed to use the ratio of the widths of syn- and anticlinal folds in the convolution horizon (Ks) to analyze the latter, in which Ks > 1 corresponds to the normal viscosity gradient, and Ks < 1, to its inversion. Convolutions of the Baltic Shield and Yakutia from Ks ≥ 1 are noted in the most liquefied sediments with unstable density stratification (sands-on-silts), which indicates the possibility of their spontaneous formation during lithogenesis. Folds with Ks ≈ 1 are widespread in Yakutia, which indicates their cryogenic genesis. Convolutions in the Tien Shan were formed with stable sediment stratification in terms of density (silts-on-sands); low-fluidized coarse-grained sediments with viscosity inversion were also involved in deformation. These features indicate the seismic initiation of liquefaction processes. The results substantiate the lithogenic genesis of convolutions in lacustrine complexes of the Baltic Shield, cryogenic and lithogenic in Yakutia, and seismogenic in the Tien Shan. It is proposed to determine the scatter of the Ks value in the diagrams for diagnosing the genesis of convolutions. For lithogenic structures, this parameter is shifted to the region with Ks > 1, and for seismites, it is relatively symmetric with respect to Ks = 1. [ABSTRACT FROM AUTHOR]

Abstract Records of palaeoearthquakes in sedimentary rocks are often debated due to the potential confusion in distinguishing seismic versus aseismic trigger mechanisms causing liquefaction. The present paper documents some unique soft-sediment deformation structures (SSDS), characterized by their extremely large size, complex morphology and preservation in coarse-grained pebbly sandstone. The SSDS are present in the Permian Barren Measures Formation, a syn-rift depositional unit within the Lower Gondwana succession in the Pranhita-Godavari Valley, eastern Peninsular India. The ~ 210 m thick succession is represented by stacked fining-up retrogradational cycles, characterized by coarse-grained trough cross-stratified pebbly sandstones near the base and fine-grained heterolithic sandstones–mudstones at the top. Each cycle signifies a change from fluvial- to tidal-influenced depositional systems. Coarse-grained pebbly sandstone beds near the base of each cycle record most SSDS, including complexly deformed layers, pseudonodules, load and flame structures, various water-escape structures like vertical/inclined sediment columns (sedimentary dykes) and contorted beds, and syn-sedimentary faults. The deformed beds are underlain and overlain by the undeformed beds. Complexly deformed SSDS are often sharply truncated at the top by undeformed beds manifesting syn-sedimentary character, which signifies that deformation took place just after deposition of the affected beds, but before deposition of the overlying beds while sedimentation was continuous. Facies analysis reveals the absence of processes like storms/pounding waves, slumps, rapid dumping (massive beds), impact shaking, volcanisms, tsunami waves or sediment gravity flows in the study area, thus negating their possibility as triggering agents for the liquefaction. The complex nature and large size of the deformation structures imply extensive liquefaction near the sediment–water interface. In addition, the deformed beds comply with most of the criteria of typical seismites. In half-graben type Gondwana basins, such seismites can be linked to palaeoearthquakes, which signify the phases of syn-rift fault reactivation, basinal sagging and associated accommodation changes.

To promote oil and gas exploration of the Carboniferous formation in the Shibei sag, the northeastern margin of Junggar Basin, recently drilled rocks from Well ZB6 with typical seismics were characterized. Through systematic core observation, the identification marks of seismites were described, a vertical sequence of seismites was established, and its oil and gas geological significance was analyzed. The results show that the seismites have typical identification marks, such as soft-sediment deformation structures (including five typical marks: liquefied stone vein, liquefied crinkled deformation structure, ball–pillow structure, flame structure and load cast, water release structure and liquefied breccia), brittle fracture structures (including three typical marks: seismic fractures, synsedimentary microfractures and seismic fracture rock) and special rock types, such as seismic grain-supported conglomerates. The stratigraphic succession reconstructed in Well ZB6 was characterized, from base to top, by (1) a basal non-seismic interval; (2) a seismic interval made up of a grain-supported conglomerate level, brittle fracture level, soft-sediment deformation level; and (3) a non-seismic interval. The discovery of seismites has oil and gas geological significance for improving reservoir performance and forming favorable source–reservoir–cap assemblages. The research describes the new reservoir genetic type and exploration direction of the Carboniferous formation in the Shibei sag (China), which has important guiding significance for the next step of oil and gas exploration.

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Soft-sediment deformation structures are present within the deep-marine fan of the West Crocker Formation, Sabah Basin, NW Borneo. Focus of this study is to highlight the impact of seismic and aseismic activities on the development of these structures and their distribution in deep-marine fan. Twenty-nine types of deformation structures were identified during the study of twelve exposed sections. These structures were grouped into five categories: i) water-escape structures, ii) sole marks, iii) clastic intrusions, iv) deformed laminations, and v) syn-depositional brittle and ductile deformation structures. The sediment deformation is interpreted to be caused either by aseismic processes like slope failure, gravity collapse, sediment overloading, density gradient, seismic induced mechanisms such as earthquakes, tectonic uplift, or combined effect of seismic and aseismic events. These structures are classified based on type of features developed during semi-consolidated phase of rock deposition. The seismite structures i.e., clastic intrusions, deformed laminations, and syn-depositional structures are correlated with active collisional tectonics during the Late Paleogene times in the Sabah Basin. In the present work, a generalized conceptual model has also been proposed for the development of soft-sediment deformation structures in a submarine fan environment. Dewatering structurers and rapid sedimentation features are associated with inner fan, load and flame structures are present within middle fan, while contorted layers, slumps and mass-transport deposits are linked with distal fan settings.

Tectonic events caused by paleoearthquakes are reflected in sediments. Outcrops and cores from the Chang-7 Member of the Late Triassic Yanchang Formation, Ordos Basin in Northern China, yield a wide variety of soft-sediment deformation structures (SSDSs), many of which are laterally extensive for more than 150 km. They include various types of folds, soft-sediment liquefaction flow deformation (liquefied sand dyke, liquefied breccia), gravity-driven deformation (load structures, ball-and-pillow structures), hydroplastic deformation (loop bedding, convolute deformation), and brittle deformation (intrastratal and stair-step faults, cracks). In most cases, deformation resulted in hybrid brittle-ductile structures exhibiting lateral variation in deformation style. These occur in delta front to semideep-to-deep lake sands and mudstones (shales). The seismites recognized in outcrops and cores indicate earthquakes with magnitudes (Ms) between 6 and 8, which are interpreted as a response to orogenic events related to the collision of the South China Block (SCB) and North China Block (NCB) during the Late Triassic period. Systematic study of the spatial and temporal distribution of these seismites improves the understanding of the tectonic context and evolutionary history of sedimentary basements. This study can provide a new perspective on the evolution of tectonic activities in the basin.

Sedimentary successions developed at the destructive plate margin settings are extremely important as they bear valuable record of contemporary basin tectonics and consequent sedimentation. Intense deformation and metamorphism often obliterate the primary sedimentary texture and structures of the sedimentary successions formed at destructive plate margins. However, sedimentological analysis of young unmetamorphosed forearc successions provides rare opportunity to infer the interplay between tectonics and sedimentation. Therefore, a process-based sedimentological facies analysis and provenance studies of the Cretaceous Pedawan Formation in the Kuching Zone, Borneo, have been undertaken for the first time. The sandstones are compositionally and texturally immature. They are normally graded with sole marks and have erosional lower contacts with mudstones and generally have gradational upper contacts. The massive sandstones, parallel-laminated sandstones, and the combination of rippled sandstones with thin mudstones are interpreted as turbidites. The lack of wave-generated structures, including hummocky cross stratification, indicates that deposition took place below storm wave base, possibly in a shelf setting. The lower part of the Pedawan Formation is mudstone dominated, and the upper part progressively becomes sandstone dominated. The Pedawan Formation bears several penecontemporaneously deformed horizons sandwiched between laterally persistent undeformed beds. Deformation structures include folds with reclined to recumbent geometry and layer-confined normal and reverse faults. We have interpreted these deformed horizons as seismites. Modal analyses of the sandstones indicate recycled orogenic as well as arc provenance and thus indicate mixing of recycled orogenic sediments with arc-derived volcanic material. The sedimentary facies characteristics of the Pedawan Formation in combination with numerous penecontemporaneous deformation features at selected stratigraphic levels indicate that the turbidites formed in a seismically active deepwater depositional setting as part of a long-lived subduction complex in eastern Sundaland during which several crustal fragments were accreted to Borneo. [ABSTRACT FROM AUTHOR]

The Barra Velha Formation, an Aptian Pre-salt unit of the Santos Basin, southeastern Brazil, is well-known for containing an important hydrocarbon reservoir. In the Atapu field, the lower part of the formation consists of laminated lutite (carbonate, siliciclastic, and hybrid), microbialite, and tufa rocks. The succession records muddy and in situ carbonate deposition in a low energy and shallow alkaline lacustrine environment in an active rift basin. Millimeter to decimeter scale soft-sediment deformation structures, faults, and fractures are very frequent and recurrent along the lutite succession. Convolute folds, loop bedding, injectites, intraclastic breccia, diastasis cracks, and associated faults, record ductile-brittle deformation in semi-lithified sediments. Normal planar and listric faults and unconfined fractures register dominant brittle deformation in lithified sediment. Foliated cataclasite and rare reverse faults record downdip slip on the hanging wall of temporarily inactive listric faults. The set of structures, the geological model, and the absence of other evident trigger mechanisms indicate that both ductile and brittle deformation are related to seismic events. The soft-sediment deformation structures are interpreted as having evolved during seismic shaking, while foliated cataclasite probably registers inter-seismic creep deformation. • Deformational structures in the lower Barra Velha Formation, Aptian Pre-salt succession, Atapu field, Santos Basin, Brazil. • Soft-sediment deformation structures, faults, and fractures. • Ductile-brittle and brittle deformation in semi-lithified and lithified sediments. • Seismites and inter-seismic foliated cataclasite. [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]

A study of a section exposed in a quarry near ​​the village of Loukhi revealed a radial kame ridge composed of horizontally layered lacustrine sands with cross-bedded sand lenses and interlayers of siltstone with a 0.2- to 1.2-m-thick horizon of convolutions occurring as wide synclines, narrow anticlines, and pseudonodules. The lacustrine sediments overlain by sand and gravel sediments with paleosols down the slope of the ridge give way to moraine boulder sands overlying the heavily dislocated strata. The objective of this work is to analyze the conditions for the formation of the kame and the deformation structures in its section as possible indicators of paleoseismicity. To account for the structural features of the section, it is proposed that the ridge formed as a result of the projection of sediments of a flowing subglacial lake, which emerged in the body of the glacier during the deglaciation period, onto the moraine. A structural analysis of reverse faults in the dislocated sediments proved their gravitational nature, which is not evident from glaciotectonics, indicating the immobility of the ice mass during ridge formation. Convolutions are developed in layers of a narrow granulometric range (fine-grained sands and silts), which is significantly different from seismites in subaqueous sediments of highly seismic regions. Therefore, these structures are not associated with seismic liquefaction, although the section is 40 km from the southwestern side of the Kandalaksha graben, where Holocene 8.0-point paleoearthquakes with moderate magnitudes were revealed. Thus, the study did not confirm the occurrence of ​​paleoearthquakes with M ≥ 6–6.5 in the study area during the Late Ice Age. [ABSTRACT FROM AUTHOR]

The Nördlinger Ries and the Steinheim Basin are widely perceived as a Middle Miocene impact crater doublet. We discovered two independent earthquake-produced seismite horizons in North Alpine Foreland Basin deposits potentially related to both impacts. The older seismite horizon, demonstrated to be associated with the Ries impact, is overlain by distal impact ejecta in situ, forming a unique continental seismite-ejecta couplet within a distance of up to 180 km from the crater. The younger seismite unit, also produced by a major palaeo-earthquake, comprises clastic dikes that cut through the Ries seismite-ejecta couplet. The clastic dikes may have formed in response to the Steinheim impact, some kyr after the Ries impact, in line with paleontologic results that indicate a time gap of about 0.5 Myr between the Ries and Steinheim events. This interpretation suggests the Ries and Steinheim impacts represent two temporally separate events in Southern Germany that, thus, witnessed a double disaster in the Middle Miocene. The magnitude–distance relationship of seismite formation during large earthquakes suggests the seismic and destructive potential of impact-induced earthquakes may be underestimated. [ABSTRACT FROM AUTHOR]

This study is concentrated on distinguishing recently exposed seismically induced sediment structures from those created in non-seismic environments. Earthquake structures documented in Hamburg (NW Germany) primarily consist of compressional forms; less frequent are structures resulting from extensional or gravitational stress. The diverse styles of these seismic deformations can be attributed to different mechanisms, e.g. compression as a result of seismic shock or of sediment intrusion, liquefaction, fluidisation, loading, or shear stress, as well as volume loss and collapse following blowout activity. Originally described two-sided flames, sandwiched occurring interlocked flames, blossom-like seismites, specific diapirs and sediment intrusions (veils) are supposed to be indicative of a seismic genesis. [ABSTRACT FROM AUTHOR]

Soft‐sediment deformation structures are abundant in the upper part of the Upper Triassic Tanzhuang Formation in the Jiyuan district, southern North China Craton. These deformation structures include large load casts, flame structures, ball‐and‐pillow structures, lenticular sand bodies, synsedimentary faults, and slump structures. The lenticular sand bodies, synsedimentary faults, and slump structures developed in the deep lake environment, while large load casts, flame structures, ball‐and‐pillow structures occurred in the deltaic environment. Based on the geometrical characteristics of the soft‐sediment deformation structures and criteria for recognizing the effects of seismic events, we exclude two major autogenic triggers (including slumping and sediment overloading) and infer that a seismic event was responsible for triggering deformation. Seismic activity was likely associated with activity on the Luanchuan Fault in the Qinling Orogen. The large size and complexity of the soft‐sediment deformation structures, together with their long distance from the inferred epicentre, indicate a high‐magnitude earthquake that is associated with the intensive uplift in the orogenic setting. Comparison of our data with soft‐sediment deformation structures from the Ordos Basin and the Yima district suggests that the Qinling Orogen was subjected to at least two phases of uplift during Late Triassic orogenesis. [ABSTRACT FROM AUTHOR]

Soft-sediment deformation structures (SSDS) including slumped beds and dewatering and diapiric structures are relatively common in the youngest part of the Triassic succession exposed on the English south coast between Seaton, Devon and Lyme Regis, Dorset. They have been attributed to fluidisation as a result of slope failure or shockwaves caused by earthquakes, storm waves or bolide impact. Few of these structures can be proved to be the result solely of a seismic event. However, diapiric structures that are restricted to a single bed and over a small area in the oldest (Rhaetian, Triassic) part of the Blue Lias formation at Pinhay Bay, Lyme Regis are morphologically similar to structures developed in present-day sediments in seismically active areas. The Pinhay Bay examples appear to have been initiated by a single event: some of them are associated with minor movements along fractures in the underlying beds. They are interpreted as the result of a small local earthquake, the last in a series of minor tectonic events in the latest Triassic that were related to the opening of the English Channel. [ABSTRACT FROM AUTHOR]

In this study, we present the work done to review the existing historical earthquake information of the Dead Sea Transform Fault Zone (DSTFZ). Several studies from various sources have been collected and reassessed, with the ultimate goal of creating of new homogenized parametric earthquake catalog for the region. We analyze 244 earthquakes between 31 BC and 1900, which are associated with the geographical buffer extending from 27 N to 36 N and from 31 E to 39 E. Of these, 93 were considered real seismic events with moment magnitude (Mw) greater than 5 that indeed occurred within this zone. While we relied on past parametric data and did not assign new macroseismic intensities, magnitude values, or epicenters for several controversial events, we did however resort to the primary sources to obtain a more critical perspective for the various assigned macroseismic intensities. In order to validate the derived parametric information, we tried to associate the events present in the historical records, with any evidence coming from past field investigations, i.e., geological or archaeological studies. Acknowledging the uneven quality and quantity of data reporting each event, we provided each entry with an uncertainty range estimate. Our catalog lists 33 events of Mw ≥ 6 absent from the latest published compilation with compatible time span and areal coverage. The whole catalog is considered complete down to Mw 7 and in certain areas down to Mw 6 after the year 1000, with majority of the larger earthquakes located in the part of DSTFZ, which extends from the southeast part of Dead Sea lake till Antioch. [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]

Records of palaeoearthquakes in sedimentary rocks are often debated due to the potential confusion in distinguishing seismic versus aseismic trigger mechanisms causing liquefaction. The present paper documents some unique soft-sediment deformation structures (SSDS), characterized by their extremely large size, complex morphology and preservation in coarse-grained pebbly sandstone. The SSDS are present in the Permian Barren Measures Formation, a syn-rift depositional unit within the Lower Gondwana succession in the Pranhita-Godavari Valley, eastern Peninsular India. The ~ 210 m thick succession is represented by stacked fining-up retrogradational cycles, characterized by coarse-grained trough cross-stratified pebbly sandstones near the base and fine-grained heterolithic sandstones–mudstones at the top. Each cycle signifies a change from fluvial- to tidal-influenced depositional systems. Coarse-grained pebbly sandstone beds near the base of each cycle record most SSDS, including complexly deformed layers, pseudonodules, load and flame structures, various water-escape structures like vertical/inclined sediment columns (sedimentary dykes) and contorted beds, and syn-sedimentary faults. The deformed beds are underlain and overlain by the undeformed beds. Complexly deformed SSDS are often sharply truncated at the top by undeformed beds manifesting syn-sedimentary character, which signifies that deformation took place just after deposition of the affected beds, but before deposition of the overlying beds while sedimentation was continuous. Facies analysis reveals the absence of processes like storms/pounding waves, slumps, rapid dumping (massive beds), impact shaking, volcanisms, tsunami waves or sediment gravity flows in the study area, thus negating their possibility as triggering agents for the liquefaction. The complex nature and large size of the deformation structures imply extensive liquefaction near the sediment–water interface. In addition, the deformed beds comply with most of the criteria of typical seismites. In half-graben type Gondwana basins, such seismites can be linked to palaeoearthquakes, which signify the phases of syn-rift fault reactivation, basinal sagging and associated accommodation changes. [ABSTRACT FROM AUTHOR]