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STUDY ON 3-D VELOCITY STRUCTURE BY TEMPORARY DENSE SEISMOSTATIONS NETWORKS OF TANGSHAN EARTHQUEKE REGION

Seismic tomography is used for processing the data of temporary seismostations networks in Tangshan region, and the velocity images of upper and mid crust in this earthquake region are obtained. The results show that, in the upper crust image, the velocity of two sides between the Tangshan fault zone are different??where the northwest side is high velocity zone while the southeast side is low and the Tangshan fault is
belt with sharp velocity variety. Besides in the mid crust velocity image, it shows that there is low velocity belt
near EW strike in the centre of the studied area, and its location and strike are corresponding with the Fengtai??Yejituo fault which is near EW strike and in Tangshan epicenter region, along both of the depth and horizon, sharp velocity variety in crust exsits too.