GPS supports the inelastic deformation of the NW corner

There has been an international symposium on GPS in Tsukuba, Japan, during Oct. 18-22, 1999. There was a poster session on the Taiwan and Turkey earthquakes. The coseismic movement associated with the Taiwan earthquake revealed by GPS has important implications for the anomalaous behavior of the NW corner.

The poster on the coseismic deformation of the Chichi Taiwan earthquake by S.-B. Yu (Inst Earth Sci, Academia Sinica) and Y.-A. Liou (National Central Univ) is impressive (The data are baesd on Central Geological Survey and Inst Earth Sci, Academia Sinica). They showed that stations along the Western Foothills east of the surface fault moved by 5 m horizontally in the WNW direction and by 3 m vertically. On the other hand, a station just southeast of the anomalous NW corner moved by 7 m horizontally in the NNW direction and by 3 m vertically.

The fact that the station southeast of the NW corner moved more than others and deviated from the earthquake slip vector may imply that the accretionary prism in this area moved in an inelastic way. Furthermore the fact that the vertical uplift is only 3 m at this station indicate that the vertical uplift amounting to 6-9 m in the NW corner is not elastic deformation, but ductile deformation of the sediment in the river bed.

　Corrections to the coseismic deformation pattern revealed by GPS data