Seismites as indicators for Holocene seismicity in the northeastern Ejina Basin, Inner Mongolia
Published:January 01, 2017
Andreas Rudersdorf, Kai Hartmann, Kaifeng Yu, Georg Stauch, Klaus Reicherter, 2017. "Seismites as indicators for Holocene seismicity in the northeastern Ejina Basin, Inner Mongolia", Seismicity, Fault Rupture and Earthquake Hazards in Slowly Deforming Regions, A. Landgraf, S. Kübler, E. Hintersberger, S. Stein
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This paper contributes to the understanding of palaeoseismology in slowly deforming regions by demonstrating the interpretation of soft-sediment deformation to be a valuable tool in identifying palaeoseismicity where the present-day seismicity is low and the geomorphology initially does not indicate active tectonics by the presence of fault scarps, surface ruptures or diverted rivers. The Ejina Basin (also known as the Gaxun Nur Basin or Juyan Lake Basin) in Inner Mongolia exhibits highly variable endorheic lakes, such as the Late Quaternary Juyanze Palaeolake. We assessed the Holocene tectonic activity of the Western Juyanze Palaeolake Basin, situated within the Ejina Basin, by identifying seismites and a previously unknown normal fault. Deformation mechanisms other than earthquakes, such as landslides or cryoturbation in permafrost, can be excluded. Far-field and near-field seismic sources are considered to have generated the soft-sediment deformation structures. As the occurrence of seismites is restricted to the Western Juyanze Palaeolake Basin and there is Pleistocene–Holocene activity on the Tienehu Fault, a near-field source is most likely.
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Seismicity, Fault Rupture and Earthquake Hazards in Slowly Deforming Regions
Palaeoseismic records and seismological data from continental interiors increasingly show that these areas of slow strain accumulation are more subject to seismic and associated natural hazards than previously thought. Moreover, some of our instincts developed for assessing hazards at plate boundaries might not apply here. Hence assessing hazards and drawing implications for the future is challenging, and how well it can be done heavily depends on the ability to assess the spatiotemporal distribution of past large earthquakes. This book explores some key issues in understanding hazards in slowly deforming areas. Examples include classic intraplate regions, such as Central and Northern Europe, Mongolia, Inner Mongolia, Australia, and North and South America, and regions of widely distributed strain, such as the Tien Shan Mountains in Central Asia. The papers in this volume are grouped into two sections. The first section deals with instrumental and historical earthquake data and associated hazard assessments. The second section covers methods from structural geology, palaeoseismology and tectonic geomorphology, and incorporates field evidence.