A New Insight into the Influence of Composition of Fault Rocks on Aseismic and Seismic Fault Slip

Active faults can slip either slowly and continuously by aseismic creep, or abruptly by a seismic event. Both slip modes of faults are closely related to the composition of fault rocks. However, the actual materials resulting in differences of slip behavior remain uncertain. The Guanxian-Anxian fault (GAF) characterized by long-term aseismic creep and the Yingxiu-Beichuan fault (YBF) slipping by large earthquakes in the Longmen Shan fault zone (LSFZ) are ideal examples for exploring the above issues. Here, in the light of observation and component analyses, we find that the distribution of carbonate minerals in both faults is distinct.

Seismic reflection evidence of crustal duplexing and lithospheric underthrusting beneath the western Qilian Mountains,northeastern margin of the Tibetan Plateau

The geological processes responsible for outward growth of the Tibetan Plateau are debated.The Qilian Mountains on the northeastern margin of the plateau comprise one of the youngest structural components of the plateau whose understanding is key to deciphering the broader geological evolution of the region.Here,based on a reprocessed deep seismic profile which was originally collected during the 1990 s across the northeast margin of the western Qilian Mountains and previous geological and geophysical data,we find evidence for decoupled crustal deformation that was partitioned by a decollement,in which lowercrustal deformation featured by local duplexing preceded upper-crustal deformation featured by imbricate thrusts.Furthermore,we propose that the Asian lithospheric mantle is being underthrust beneath the western Qilian Mountains,as inferred from patterns of lower crustal deformation which is marked by the Moho geometry.Integrating these results yields a better understanding of lithospheric deformation of western Qilian Mountains,northeastern margin of the plateau during the Cenozoic.