Seismites as indicators for Holocene seismicity in the northeastern Ejina Basin, Inner Mongolia

Abstract

AbstractThis 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.