Geological and geomorphological evidence for active faulting of the southern Liupanshan fault zone, NE Tibetan Plateau

Abstract

Abstract The southern Liupanshan fault zone (SLFZ) has been active during the Holocene and accommodates complex deformation between the compressional Liupanshan Mountain and the extensional Weihe Graben. We characterized the active faulting of the SLFZ using interpretations of high-resolution satellite images, digital elevation models derived from structure-from-motion models, combined with field investigations. The presence of well-preserved linear fault troughs, scarps, knickpoints, offset streams and ridges, and landslides along the SLFZ indicate that surface-rupturing earthquakes have occurred along the SLFZ in the Holocene. Evidence from paleoseismic trenching indicates that the most recent earthquake occurred between 1607\u202f±\u202f77\u202fBCE and 1070\u202f±\u202f90\u202fCE, and thus may have been the 600\u202fCE historical earthquake. The estimated magnitude of this earthquake is Mw\u202f6.7. Radiometric dating of an offset fluvial terrace indicates a late Pleistocene to Holocene left-lateral slip rate of ~1.5\u202f±\u202f0.3\u202fmm/yr. Our geologic and geomorphic observations show that the SLFZ may extend into the Weihe Graben where the slip is transferred onto other active faults within the Weihe Graben.