关键词: 昌马, 反S型, 破裂错动过程

Abstract: Based on the investigation and analysis of the macroscopic ground rupture zone caused by Changma earthquake(M_s =7.5)which occurred in the western Qilian Mountains, Gansu province on December 25, 1932. and combining the information relative to fault activity with the results of lab modelling experiments, this paper pays much attention to the discussion of the tectonic evolution of Changma causative fault and the rupture slip process at the places of stress concentration within seismogenic fault.The rupture zone on ground caused by the event, with a NWW of trend and a length of more than 120 km, consists of three reversed-S-shaped seismic demation belts, and coincides with the Quaternary active trace of Changma faults. Both field geological information and modelling experiments have indicated that the concaves of the turning sectors of the reversed-S-shaped faults are the places at which the stress and strain would be concentrated easily. Here, a model of the multi-initiative points of the rupture slip within Changma seismogenic fault has been suggested, i. e., when the Changma event occurred, each of the concaves of the above kinds ruptured initiatively, then was developing along the above-mentioned reversed-S-shaped fault's trace so as to form the whole Changma seismic fault.

Key words: Changma, Peversed-S-shaped, Rupture slip process