Objective Betula microphylla Bunge, as a resource treasury of desert biodiversity, is a pioneer plant in saline-alkaline soil amelioration. According to previous research, Ebinur Lake, north Xinjiang, is a representat...Objective Betula microphylla Bunge, as a resource treasury of desert biodiversity, is a pioneer plant in saline-alkaline soil amelioration. According to previous research, Ebinur Lake, north Xinjiang, is a representative saltwater lake with 92–131 g/L salinity(Li et al., 2006).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 eastern margin of the Tibetan Plateau is characterized by frequent earthquakes; however, research of paleo-earthquakes in the area has been limited^ owing to the alpine topography and strong erosion. Detailed inve...The eastern margin of the Tibetan Plateau is characterized by frequent earthquakes; however, research of paleo-earthquakes in the area has been limited^ owing to the alpine topography and strong erosion. Detailed investigations of soft-sediment deformation(SSD) structures are valuable for understanding the trigger mechanisms, deformation processes, and the magnitudes of earthquakes that generate such structures, and help us to understand tectonic activity in the region. To assess tectonic activity during the late Quaternary, we studied a well-exposed sequence of Shawan lacustrine sediments, 7.0 m thick, near Lake Diexi in the upper reaches of the Minjiang River. Deformation is recorded by both ductile structures(load casts, flame structures,pseudonodules, ball-and-pillow structures, and liquefied convolute structures) and brittle structures(liquefied breccia, and microfaults). Taking into account the geodynamic setting of the area and its known tectonic activity, these SSD structures can be interpreted in terms of seismic shocks. The types and forms of the structures,the maximum liquefaction distances, and the thicknesses of the horizons with SSD structures in the Shawan section indicate that they record six strong earthquakes of magnitude 6-7 and one with magnitude >7. A recent study showed that the Songpinggou fault is the seismogenic structure of the 1933 Ms7.5 Diexi earthquake. The Shawan section is located close to the junction of the Songpinggou and Minjiang faults, and records seven earthquakes with magnitudes of ?7. We infer,therefore, that the SSD structures in the Shawan section document deglacial activity along the Songpinggou fault.展开更多
With the objective of establishing a distinction between deformation structures caused by freeze/thaw cycles and those resulting from seismic activity, we studied three well–exposed alluvial deposits in a section at ...With the objective of establishing a distinction between deformation structures caused by freeze/thaw cycles and those resulting from seismic activity, we studied three well–exposed alluvial deposits in a section at Dogai Coring, northern Qiangtang Basin, Tibetan Plateau. Deformation is present in the form of plastic structures(diapirs, folds and clastic dykes), brittle structures(micro–faults) and cryogenic wedges. These soft–sediment deformation features(except the micro–faults) are mainly characterized by meter–scale, non–interlayered, low–speed and low–pressure displacements within soft sediments, most commonly in the form of plastic deformation. Taking into account the geographic setting, lithology and deformation features, we interpret these soft–sediment deformation features as the products of freeze/thaw cycles, rather than of earthquake–induced shock waves, thus reflecting regional temperature changes and fluctuations of hydrothermal conditions in the uppermost sediments. The micro–faults(close to linear hot springs) are ascribed to regional fault activity;however, we were unable to identify the nature of the micro–faults, perhaps due to disturbance by subsequent freeze/thaw cycles. This study may serve as a guide to recognizing the differences between deformation structures attributed to freeze/thaw cycles and seismic processes.展开更多
General history of disasters in China suggests that China has frequently experienced two major natural disasters in its long history,one is from catastrophic earthquake events,and the other is from extreme climatic ev...General history of disasters in China suggests that China has frequently experienced two major natural disasters in its long history,one is from catastrophic earthquake events,and the other is from extreme climatic events,due to its unique active tectonic environment and climatic complexity.Although these two major natural disasters have caused great damage to human society,it remains unclear whether and how they affect Chinese dynasty alternation on decadal(emperor)timescales.Based on detailed comparisons between abrupt climatic changes,catastrophic seismic activities,and the history of Chinese dynasty alternation from 1000–2000 AD,we conclude that on decadal timescales,extreme drought(and/or flood)events could indeed significantly reduce agricultural production,cause severe food shortages and famine,and result in increases in population exile,rising food prices and inflation,and insufficient supplies for military defense,which could exceed social resilience and eventually lead to financial risks and social upheavals of the dynasties.In addition,catastrophic seismic events in the densely populated,agricultural areas of China,including the 1303 surface wave magnitude(M_(s))8.0 Hongtong earthquake,the 1556 M_(s)8.25Huaxian earthquake and the 1920 M_(s)8.5 Haiyuan earthquake,caused more than 200,000casualties and millions of victims to live in exile which was almost equivalent to the order of magnitude of those extreme climatic events-induced refugees.The secondary geological hazards related to the earthquakes(e.g.,extensive landslides and soil erosion),which could last for decades,caused more casualties and reduced food production.Furthermore,great plague spread caused by the casualties could significantly increase psychological panic among the survivors,resulting in social instability.Therefore,catastrophic seismic events could also accelerate the collapse of the dynasties(e.g.,the Ming dynasty)without immediate mitigation measures.This study indicates that catastrophic seismic activities,as well as extreme climatic events,could have great effects on the social structures and thus on the Chinese dynasty alternation on decadal timescales,which highlights the far-reaching implications of geological hazard research.展开更多
基金jointly funded by the special project of the fundamental scientific research of the Institute of Geology, China Earthquake Administration (Grant No. IGCEA2121)the National Natural Science Foundation of China (Grant No. 41572331, 41272386)。
文摘Objective Betula microphylla Bunge, as a resource treasury of desert biodiversity, is a pioneer plant in saline-alkaline soil amelioration. According to previous research, Ebinur Lake, north Xinjiang, is a representative saltwater lake with 92–131 g/L salinity(Li et al., 2006).
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.
基金the joint support by the National Natural Science Foundation of China(41807298,41672211,41572346)the Special Project of Fundamental Scientific Research of the Institute of Geology,China Earthquake Administration(IGCEA1713)
文摘The eastern margin of the Tibetan Plateau is characterized by frequent earthquakes; however, research of paleo-earthquakes in the area has been limited^ owing to the alpine topography and strong erosion. Detailed investigations of soft-sediment deformation(SSD) structures are valuable for understanding the trigger mechanisms, deformation processes, and the magnitudes of earthquakes that generate such structures, and help us to understand tectonic activity in the region. To assess tectonic activity during the late Quaternary, we studied a well-exposed sequence of Shawan lacustrine sediments, 7.0 m thick, near Lake Diexi in the upper reaches of the Minjiang River. Deformation is recorded by both ductile structures(load casts, flame structures,pseudonodules, ball-and-pillow structures, and liquefied convolute structures) and brittle structures(liquefied breccia, and microfaults). Taking into account the geodynamic setting of the area and its known tectonic activity, these SSD structures can be interpreted in terms of seismic shocks. The types and forms of the structures,the maximum liquefaction distances, and the thicknesses of the horizons with SSD structures in the Shawan section indicate that they record six strong earthquakes of magnitude 6-7 and one with magnitude >7. A recent study showed that the Songpinggou fault is the seismogenic structure of the 1933 Ms7.5 Diexi earthquake. The Shawan section is located close to the junction of the Songpinggou and Minjiang faults, and records seven earthquakes with magnitudes of ?7. We infer,therefore, that the SSD structures in the Shawan section document deglacial activity along the Songpinggou fault.
基金supported by projects from the National Natural Science Foundation of China (41807298, 41702372, 41672211)the China Postdoctoral Science Foundation (2019M650788)+2 种基金National Key Research and Development Project of China (2016YFC0600310)the China Geological Survey (DD20160022, DD20190059)the Basic Research Funds (JYYWF201810) of the Institute of Geology, CAGS.
文摘With the objective of establishing a distinction between deformation structures caused by freeze/thaw cycles and those resulting from seismic activity, we studied three well–exposed alluvial deposits in a section at Dogai Coring, northern Qiangtang Basin, Tibetan Plateau. Deformation is present in the form of plastic structures(diapirs, folds and clastic dykes), brittle structures(micro–faults) and cryogenic wedges. These soft–sediment deformation features(except the micro–faults) are mainly characterized by meter–scale, non–interlayered, low–speed and low–pressure displacements within soft sediments, most commonly in the form of plastic deformation. Taking into account the geographic setting, lithology and deformation features, we interpret these soft–sediment deformation features as the products of freeze/thaw cycles, rather than of earthquake–induced shock waves, thus reflecting regional temperature changes and fluctuations of hydrothermal conditions in the uppermost sediments. The micro–faults(close to linear hot springs) are ascribed to regional fault activity;however, we were unable to identify the nature of the micro–faults, perhaps due to disturbance by subsequent freeze/thaw cycles. This study may serve as a guide to recognizing the differences between deformation structures attributed to freeze/thaw cycles and seismic processes.
基金National Nonprofit Fundamental Research Grant of China,Institute of Geology,China Earthquake Administration,No.IGCEA2009。
文摘General history of disasters in China suggests that China has frequently experienced two major natural disasters in its long history,one is from catastrophic earthquake events,and the other is from extreme climatic events,due to its unique active tectonic environment and climatic complexity.Although these two major natural disasters have caused great damage to human society,it remains unclear whether and how they affect Chinese dynasty alternation on decadal(emperor)timescales.Based on detailed comparisons between abrupt climatic changes,catastrophic seismic activities,and the history of Chinese dynasty alternation from 1000–2000 AD,we conclude that on decadal timescales,extreme drought(and/or flood)events could indeed significantly reduce agricultural production,cause severe food shortages and famine,and result in increases in population exile,rising food prices and inflation,and insufficient supplies for military defense,which could exceed social resilience and eventually lead to financial risks and social upheavals of the dynasties.In addition,catastrophic seismic events in the densely populated,agricultural areas of China,including the 1303 surface wave magnitude(M_(s))8.0 Hongtong earthquake,the 1556 M_(s)8.25Huaxian earthquake and the 1920 M_(s)8.5 Haiyuan earthquake,caused more than 200,000casualties and millions of victims to live in exile which was almost equivalent to the order of magnitude of those extreme climatic events-induced refugees.The secondary geological hazards related to the earthquakes(e.g.,extensive landslides and soil erosion),which could last for decades,caused more casualties and reduced food production.Furthermore,great plague spread caused by the casualties could significantly increase psychological panic among the survivors,resulting in social instability.Therefore,catastrophic seismic events could also accelerate the collapse of the dynasties(e.g.,the Ming dynasty)without immediate mitigation measures.This study indicates that catastrophic seismic activities,as well as extreme climatic events,could have great effects on the social structures and thus on the Chinese dynasty alternation on decadal timescales,which highlights the far-reaching implications of geological hazard research.
