Soft-sediment deformation structures induced by seismic liquefaction and/or fluidization receive much attention in sedimentological,structural and palaeoseismic studies.The direct record of larger earthquakes is restr...Soft-sediment deformation structures induced by seismic liquefaction and/or fluidization receive much attention in sedimentological,structural and palaeoseismic studies.The direct record of larger earthquakes is restricted to instrumental and historical data; the recognition of prehistoric earthquakes requires criteria to recognize seismites in the geological record.The areal distribution of seismites can sometimes be related to active faults since distances to the epicenter(for a given magnitude) tend to be related to the liquefaction effects of seismic shocks.The use of soft-sediment deformation structures for palaeoseismic studies has limitations,however.Hardly anything is known,for instance,about the effects that modern seismic events have on the sediments in most environments.Moreover,criteria for the recognition of seismites are still under discussion.The following characteristics seem,particularly in combination,the most reliable:(1) Soft-sediment deformation structures should occur in laterally continuous,preferably recurring horizons,separated by undeformed beds;(2) These deformation structures should be comparable with structures known to have been triggered by modern seismic activity;(3) The sedimentary basin should have experienced tectonic activity at the time when the deformations were formed; and(4) The intensity or abundance of the soft-sediment deformation structures in a presumed seismite should change laterally,depending on the distance to the epicenter.It turns out that all of these four criteria have important exceptions.(1) Soft-sediment deformation structures occurring over large lateral distances in a specific layer can be triggered also by other processes.Moreover,in environments with a low sedimentation rate,the time between successive earthquakes is often too short to allow accumulation of beds that remain undisturbed.Furthermore,total liquefaction of a sandy bed may result in the absence of deformation features.(2) No truly diagnostic soft-sediment deformation structures exist to prove展开更多
This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation stru...This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.展开更多
The Mesoproterozoic Wumishan Formation, composed of dolomite is a widely distributed stratigraphic unit in the Beijing area. It was formed over a long period of time in the Yan-Liao aulacogen, a stable peritidal envir...The Mesoproterozoic Wumishan Formation, composed of dolomite is a widely distributed stratigraphic unit in the Beijing area. It was formed over a long period of time in the Yan-Liao aulacogen, a stable peritidal environment that was ideal for recording earthquakes in the form of soft-sediment deformation structures (SSDS). Numerous examples occur in the upper part of the Wumishan Formation, along the Yongding River Valley. In addition, brittle structures include intrastratal fault and seismically cracked breccias. The soft-sediment deformation structures include liquefied features (diapirs, clastic dykes, convolute bedding), compressional deformation features (accordion folds, plate-spine breccias, mound-and-sag structures), and extensional plastic features (loop-bedding). Based on the regional geological setting and previous research, movements along the main axial fault of the Yan-Liao aulacogen are considered as the triggers for earthquakes since the Early Mesoproterozoic. The number and distribution of the SSDS suggest the major earthquake frequency in the Wumishan Formation of 20 to 32 thousand years.展开更多
An earthquake of magnitude M5.7 occurred in Yamutu village,Songyuan City,Jilin Province,NE China(45°16′12″N/124°42′35″E)on May 28,2018,with a focal depth of 13 km.The epicenter is located at the intersec...An earthquake of magnitude M5.7 occurred in Yamutu village,Songyuan City,Jilin Province,NE China(45°16′12″N/124°42′35″E)on May 28,2018,with a focal depth of 13 km.The epicenter is located at the intersection of the Fuyu/Songyuan-Zhaodong Fault,Second Songhua River Fault and Fuyu North Fault which lies northwest of TanchengLujiang Fault(Tan-Lu Fault).The earthquake-induced widespread liquefaction structures and ground surface fissures within 3 km from the epicenter,caused serious disasters to the local surroundings.The visible liquefied structures include sand volcanoes,liquefied sand mounds,sand dikes and sand sills.Sand volcanoes can be divided into sand volcano with a crater,sand volcano without a crater and water volcano(no sand).Other soft-sediment deformation structures(SSDS)induced by the earthquake include deformation lamination,load and flame structures,deformation folds,dish structures,convolute bedding and water-escape structures.The formation process of the sand volcanoes comprises three stages:(1)building up excess pore-fluid pressure in the liquefied layer,(2)cracking of the low-permeable overlying layer,and(3)mixture of sand-water venting out of the ground surface.During the upward movement,the liquefied sand is injected into the low-permeable layer to form sand veins,sand sills and various types of deformation structures.Vertical distribution of seismic liquefaction structure can be divided into four zones:the thoroughly liquefied zone,the lower liquefied zone with SSDS,the upper liquefied zone with SSDS,and the ground surface liquefied zone.The liquefaction occurred at a burial depth of 2–5 m,and the thickness of liquefied sand is 2 m.NE-SW(35°–215°)trending compressive stress is possibly the seismogenic trigger of the Songyuan M5.7 earthquake that caused the fault(Fuyu/Songyuan-Zhaodong Fault)to reactivate.The study of the Songyuan seismic liquefaction structures gives insight into the prediction of modern earthquakes and disasterprone areas.Meanwhile it provides abundant basic ma展开更多
It is demonstrated here for the first time how Palaeoproterozoic stromatolites survived seismic disturbance of their substrate. The stromatolites under study could have been cyanobacteria or any other photo-autotrophi...It is demonstrated here for the first time how Palaeoproterozoic stromatolites survived seismic disturbance of their substrate. The stromatolites under study could have been cyanobacteria or any other photo-autotrophic microbes, which formed mats that covered a substrate of very fine-grained sandstones and mudstones of the Chaibasa Fm. in eastern India. The sediments represent a shelf environment. The local abundance of the stromatotites suggests that the tow-energy environment formed a suitable habitat. The common phases of tectonic quiescence were, however, occasionally interrupted by seismic shocks. These were sufficiently strong to deform the mat layers, the tower parts of which might already have been （semi-） consolidated. The mats became partly folded, partly faulted, and already consolidated parts of the stromatotite layers broke off. This can be deduced from the angular shapes of part of the broken-off fragments. It appears, however, that part of these fragments were stilt sufficiently soft to become rounded and deformed by rotting over the seafloor, probably under the influence of tidal currents. When come to rest, these fragments served as a new substrate for new generations of the microorganisms. These micro-organisms thus survived by continued growth on the reworked fragments and built up new stromatolites that may show an ‘angular disconformity＇ with the stromatotites of their substrate. It thus is shown that stromatotites have an adequate response to a sudden disturbance of their habitat, and that they survive earthquakes by colonization of broken-off fragments. We call the ‘healed＇ fragments ‘tombotiths＇ （tumbled stones）.展开更多
The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help recon...The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abundant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identification of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.展开更多
The study on soft-sediment deformation structures(SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years,and SSDS developed in turbidite system in the Laiyang Grou...The study on soft-sediment deformation structures(SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years,and SSDS developed in turbidite system in the Laiyang Group are widely known by domestic researchers.However,few studies were conducted on the SSDS in fan delta system in the Qingshan Group,Lingshan Island.This study analyzes the classification and characteristics of SSDS especially their lithofacies association and tithologic characteristics through field outcrops investigation and thin section analysis as well.A conclusion was acquired that the paleoenvironment was a fan delta system with occurrence of several volcanic eruptions,where the water became gradually shallower.The SSDS types in the Qingshan Group includes load and flame structure,ball and pillow structure,waterescape structure,hydroplastic deformation structure,plastic sandstone breccia structure,volcanic drop stone and V-shaped ground fissure mainly caused by volcanic earthquakes of three types:(1)seismic waves,(2)gravity and inertia effect of pyroclastic flows,(3)instant differential air pressure;which is different from slumping and tectonic earthquakes occurred in the Laiyang Group.In addition,with the lithofacies association analysis between pyroclastic flow and SSDS beds,a distribution model of SSDS related to volcanic earthquakes can be established:SSDS types changed gradually with their distance further away from the volcanic activity core.Brittle deformation which was common in the proximal zone disappeared gradually;liquefied and plastic SSDS continued to dominate in the medial zone;and slightly liquefied SSDS were developed in the distal zone.Meanwhile,the scale and size of SSDS is negatively correlated with the distance of SSDS depositional locations from the volcanic vent.展开更多
Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist ...Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist of fluidized deformation, synsedimentary faults, seismo-folds and plastic deformation; the Mantou Formation is dominated by small-scale horst faults, intruded dikes, fluidized veins, and seismo-cracks. These structures are demonstrated to be earthquake-related by analysis of trigger mechanisms, and may indicate the activity of the Qinling tectonic belt during the early Cambrian. Furthermore, the assemblages of soft-sediment deformation structures altered with time： large-scale, intense deformation in the Zhushadong Formation alters to small-scale, weak deformation in the Mantou Formation. This striking feature may have been caused by changes in hypocentral depth from deep-focus to shallow-focus earthquakes, indicating that the Qinling tectonic belt developed from the subduction of the Shangdan Ocean to the extension of the Erlangping back-arc basin. This study suggests that soft-sediment deformation structures can be used to reveal the activity of a tectonic belt, and, more importantly, changes in deformation assemblages can track the evolution of a tectonic belt.展开更多
文摘Soft-sediment deformation structures induced by seismic liquefaction and/or fluidization receive much attention in sedimentological,structural and palaeoseismic studies.The direct record of larger earthquakes is restricted to instrumental and historical data; the recognition of prehistoric earthquakes requires criteria to recognize seismites in the geological record.The areal distribution of seismites can sometimes be related to active faults since distances to the epicenter(for a given magnitude) tend to be related to the liquefaction effects of seismic shocks.The use of soft-sediment deformation structures for palaeoseismic studies has limitations,however.Hardly anything is known,for instance,about the effects that modern seismic events have on the sediments in most environments.Moreover,criteria for the recognition of seismites are still under discussion.The following characteristics seem,particularly in combination,the most reliable:(1) Soft-sediment deformation structures should occur in laterally continuous,preferably recurring horizons,separated by undeformed beds;(2) These deformation structures should be comparable with structures known to have been triggered by modern seismic activity;(3) The sedimentary basin should have experienced tectonic activity at the time when the deformations were formed; and(4) The intensity or abundance of the soft-sediment deformation structures in a presumed seismite should change laterally,depending on the distance to the epicenter.It turns out that all of these four criteria have important exceptions.(1) Soft-sediment deformation structures occurring over large lateral distances in a specific layer can be triggered also by other processes.Moreover,in environments with a low sedimentation rate,the time between successive earthquakes is often too short to allow accumulation of beds that remain undisturbed.Furthermore,total liquefaction of a sandy bed may result in the absence of deformation features.(2) No truly diagnostic soft-sediment deformation structures exist to prove
基金financially supported by the National Natural Science Foundation of China (41702372)the Open Fund of State Key Laboratory of Earthquake Dynamics (LED2017B03)
文摘This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.
文摘The Mesoproterozoic Wumishan Formation, composed of dolomite is a widely distributed stratigraphic unit in the Beijing area. It was formed over a long period of time in the Yan-Liao aulacogen, a stable peritidal environment that was ideal for recording earthquakes in the form of soft-sediment deformation structures (SSDS). Numerous examples occur in the upper part of the Wumishan Formation, along the Yongding River Valley. In addition, brittle structures include intrastratal fault and seismically cracked breccias. The soft-sediment deformation structures include liquefied features (diapirs, clastic dykes, convolute bedding), compressional deformation features (accordion folds, plate-spine breccias, mound-and-sag structures), and extensional plastic features (loop-bedding). Based on the regional geological setting and previous research, movements along the main axial fault of the Yan-Liao aulacogen are considered as the triggers for earthquakes since the Early Mesoproterozoic. The number and distribution of the SSDS suggest the major earthquake frequency in the Wumishan Formation of 20 to 32 thousand years.
基金supported by the“Natural Science Foundation of Heilongjiang Province(No.JJ2016ZR0573)”“Youth Foundation of Northeast Petroleum University(No.NEPUBS201503)”+2 种基金“Northeast Petroleum University Scientific Research Start-up Fund”“Shandong Provincial Key Laboratory of Depositional Mineralization and Mineral Foundation(No.DMSMZO17009)”“Natural Science Foundation of Shandong Province(No.ZR2016DB15)”.
文摘An earthquake of magnitude M5.7 occurred in Yamutu village,Songyuan City,Jilin Province,NE China(45°16′12″N/124°42′35″E)on May 28,2018,with a focal depth of 13 km.The epicenter is located at the intersection of the Fuyu/Songyuan-Zhaodong Fault,Second Songhua River Fault and Fuyu North Fault which lies northwest of TanchengLujiang Fault(Tan-Lu Fault).The earthquake-induced widespread liquefaction structures and ground surface fissures within 3 km from the epicenter,caused serious disasters to the local surroundings.The visible liquefied structures include sand volcanoes,liquefied sand mounds,sand dikes and sand sills.Sand volcanoes can be divided into sand volcano with a crater,sand volcano without a crater and water volcano(no sand).Other soft-sediment deformation structures(SSDS)induced by the earthquake include deformation lamination,load and flame structures,deformation folds,dish structures,convolute bedding and water-escape structures.The formation process of the sand volcanoes comprises three stages:(1)building up excess pore-fluid pressure in the liquefied layer,(2)cracking of the low-permeable overlying layer,and(3)mixture of sand-water venting out of the ground surface.During the upward movement,the liquefied sand is injected into the low-permeable layer to form sand veins,sand sills and various types of deformation structures.Vertical distribution of seismic liquefaction structure can be divided into four zones:the thoroughly liquefied zone,the lower liquefied zone with SSDS,the upper liquefied zone with SSDS,and the ground surface liquefied zone.The liquefaction occurred at a burial depth of 2–5 m,and the thickness of liquefied sand is 2 m.NE-SW(35°–215°)trending compressive stress is possibly the seismogenic trigger of the Songyuan M5.7 earthquake that caused the fault(Fuyu/Songyuan-Zhaodong Fault)to reactivate.The study of the Songyuan seismic liquefaction structures gives insight into the prediction of modern earthquakes and disasterprone areas.Meanwhile it provides abundant basic ma
基金project was supported by the Foundation Dr Schurmannfonds,grants no.34/2006 and 57/2009,67/2010 and 82/2012the DST and the Department of Geology,Calcutta University for financial support and infrastructural support
文摘It is demonstrated here for the first time how Palaeoproterozoic stromatolites survived seismic disturbance of their substrate. The stromatolites under study could have been cyanobacteria or any other photo-autotrophic microbes, which formed mats that covered a substrate of very fine-grained sandstones and mudstones of the Chaibasa Fm. in eastern India. The sediments represent a shelf environment. The local abundance of the stromatotites suggests that the tow-energy environment formed a suitable habitat. The common phases of tectonic quiescence were, however, occasionally interrupted by seismic shocks. These were sufficiently strong to deform the mat layers, the tower parts of which might already have been （semi-） consolidated. The mats became partly folded, partly faulted, and already consolidated parts of the stromatotite layers broke off. This can be deduced from the angular shapes of part of the broken-off fragments. It appears, however, that part of these fragments were stilt sufficiently soft to become rounded and deformed by rotting over the seafloor, probably under the influence of tidal currents. When come to rest, these fragments served as a new substrate for new generations of the microorganisms. These micro-organisms thus survived by continued growth on the reworked fragments and built up new stromatolites that may show an ‘angular disconformity＇ with the stromatotites of their substrate. It thus is shown that stromatotites have an adequate response to a sudden disturbance of their habitat, and that they survive earthquakes by colonization of broken-off fragments. We call the ‘healed＇ fragments ‘tombotiths＇ （tumbled stones）.
基金the National Institute of Natural Hazards,Ministry of Emergency Management of China(ZDJ2019-21)the National Natural Science Foundation of China(Nos.41872227 and 41602221).
文摘The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abundant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identification of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.
文摘The study on soft-sediment deformation structures(SSDS) of Lingshan Island has been one of the hot topics of sedimentology researches in China in recent years,and SSDS developed in turbidite system in the Laiyang Group are widely known by domestic researchers.However,few studies were conducted on the SSDS in fan delta system in the Qingshan Group,Lingshan Island.This study analyzes the classification and characteristics of SSDS especially their lithofacies association and tithologic characteristics through field outcrops investigation and thin section analysis as well.A conclusion was acquired that the paleoenvironment was a fan delta system with occurrence of several volcanic eruptions,where the water became gradually shallower.The SSDS types in the Qingshan Group includes load and flame structure,ball and pillow structure,waterescape structure,hydroplastic deformation structure,plastic sandstone breccia structure,volcanic drop stone and V-shaped ground fissure mainly caused by volcanic earthquakes of three types:(1)seismic waves,(2)gravity and inertia effect of pyroclastic flows,(3)instant differential air pressure;which is different from slumping and tectonic earthquakes occurred in the Laiyang Group.In addition,with the lithofacies association analysis between pyroclastic flow and SSDS beds,a distribution model of SSDS related to volcanic earthquakes can be established:SSDS types changed gradually with their distance further away from the volcanic activity core.Brittle deformation which was common in the proximal zone disappeared gradually;liquefied and plastic SSDS continued to dominate in the medial zone;and slightly liquefied SSDS were developed in the distal zone.Meanwhile,the scale and size of SSDS is negatively correlated with the distance of SSDS depositional locations from the volcanic vent.
基金granted by the doctor foundation of Henan Polytechnic University(NO:B2013-076)the National Nature Science Foundation of China(NO:4147208341440016)
文摘Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist of fluidized deformation, synsedimentary faults, seismo-folds and plastic deformation; the Mantou Formation is dominated by small-scale horst faults, intruded dikes, fluidized veins, and seismo-cracks. These structures are demonstrated to be earthquake-related by analysis of trigger mechanisms, and may indicate the activity of the Qinling tectonic belt during the early Cambrian. Furthermore, the assemblages of soft-sediment deformation structures altered with time： large-scale, intense deformation in the Zhushadong Formation alters to small-scale, weak deformation in the Mantou Formation. This striking feature may have been caused by changes in hypocentral depth from deep-focus to shallow-focus earthquakes, indicating that the Qinling tectonic belt developed from the subduction of the Shangdan Ocean to the extension of the Erlangping back-arc basin. This study suggests that soft-sediment deformation structures can be used to reveal the activity of a tectonic belt, and, more importantly, changes in deformation assemblages can track the evolution of a tectonic belt.
