Why did a large uplift appear at the NW corner?

The amount of surface uplift due to thrusting was largest at the NW corner of the earthquake fault plane. Here the fall appeared across the river, and the dam was destructed by the surface fault. The vertical displacement of the dam wall is probably amounting to about 10 m. In this corner area, multiple thrusts and buldges appeared. It seems difficult to explain such large displacement in a local area by the elastic dislocation theory. Although an oblique slip can produce a larger amount of uplift at the NW part of the fault plane, the wavelength of such uplift is quite large.

The pecularity of this corner can be explained, if we assume a ductile behavior of the material of the hanging wall, like seen at the athletic field further to the south.

By the strike-slip component of the NW motion of the hanging wall, the direction of the motion changes to the north and to the west, because the soft material collides with the underthrusting wall or the northern stationary block. Then it is accumulated at the NW corner. Note also here is the place where we found the anomolous slip directions.