Seismicity and quaternary faulting in China

Abstract

Quaternary faulting, based on an interpretation of a mosaic of LANDSAT-1 imagery, and seismicity demonstrate a distinct difference in Quaternary tectonics between western and eastern China. Maps of the faulting, of all earthquakes reported in historical records for 1177 B.C. to 1903 A.D., of earthquakes determined from instrumental data for 1904 to February 1975, and of all earthquakes with M ≧ 6 from 1177 B.C. to Feburary 1975 are presented. East-west trending reactivated Paleozoic mountain belts and subparallel large left-lateral strike-slip faults predominate in western China. The northeasterly trending Cenozoic Shansi graben and subparallel right-lateral strike-slip faults characterize eastern China. Nearly aseismic blocks occur in both east and west, but a satisfactory model of small plates that explains all of the observed seismotectonic phenomena is not apparent. The tectonic activity may be controlled by stresses from nearby plate margins, with the collision of India and Eurasia predominating. Large earthquakes and surface faulting have occurred on some of the faults observed in the satellite images. Because the Chinese historical record suggests the alternation of seismically active and quiet periods of the order of a few hundred years in continental intraplate areas, data on Quaternary faulting can be especially valuable in supplementing short records of seismicity in order to understand tectonics and to evaluate seismic risk.