Active model, deformation characteristics and dynamic mechanism of the Yingxiu – Nanba segment in the MS 8.0 seismic fault

摘要

Wenchuan MS 8.0 earthquake happened 0n May 12th 2008, which was mainly caused by the activity of the Central Fault Belt. What aspects did surface rupture characteristics of this earthquake manifest? According to the surface rupture belts, deformation characteristics, kinematic characteristics and aftershock migration characteristics formed by Wenchuan MS 8.0 earthquake along theYingxiu – Nanba segment of Central Fault Belt On May 12th 2008, combined with the former’ study about physical character of the shallow and deep part of the fault, the research result showed: (1) FromYingxiu to Nanba, the faulting mode changed from reverse-thrusting to reverse-thrusting with right lateral slip and to the component of right lateral striking slip correspond to the component of thrust, and was accompanied by a weak rotation between the two walls of the fau (2) On the whole, the northeast direction striking fault was dominated by thrusting with right lateral slipping, while locally there was northwest direction thrusting with left lateral striking slip, as was the result of the east-west direction stress; (3) The seismic cracks, the distribution of aftershocks and the deformation characteristics of the overlapped shortening on the earth’s surface revealed that the rupture and strain energy releasing resulted from the combined action of region tectonic stress in near east-west direction and local tectonic stress in northeast direction; (4) Under the geological background of nearly east-west direction exceptional density zone and the fault plane dipping to east-west direction, plateau matter creepaging to the east along the slip layer led to nearly east-west direction stress and brought the Wenchuan MS 8.0 earthquake, and whose energy regulation behaved as the active method of Longmenshan Fault.