Spatial and temporal variations in types of seismotectonic deformations of the Earth's crust in the San Andreas fault zone, northern California

摘要

A method of seismic regionalization is proposed on the basis of the predominant occurrence of three main types of fracture in earthquake sources, and properties of seismotectonic crustal deformation in the San Andreas fault zone (northern California) are analyzed with the use of data on focal mechanisms. The main feature of motions in earthquake sources of this region consists in the prevalence of strike-slip and normal faulting, whereas the relative contribution of reversed faulting to the tectonic deformation of the region is insignificant. Based on the predominant type of motions in earthquake sources, the San Andreas fault can be classified as a strike-slip zone. The strike-slip motions persist to a depth of 15 km. Areas of predominantly normal fault motions in earthquake sources adjoin the San Andreas fault on its periphery. The only area of predominantly reversed-fault motions in earthquake sources is identified in the San Andreas fault zone (the San Francisco area) at depths greater than 5 km.