Shallow velocity structure and hidden faults　of Kunming city region

摘要

In order to image the 3-D velocity structure of its shallow crust in Ktmming region, China, finite-difference seismic tomography is used to invert the seismic data selected carefully from six-shot data. The result lays a founda-tion for the discussion of the relationship between the obtained velocity structure and the hidden faults, and for the illumination of the depth extents of main active faults surrounding Kunming city. Puduhe-Xishan fault lies on the western margin of the Kunming basin and is just situated on the west edge of the low velocity anomaly zone found at all depth levels. This indicates that this fault is a borderline fault of the Kunming basin. It can be concluded that the fault dips eastwards with a steep angle and its depth extent is large. Puji-Hanjiacun fault and Heilong-tan-Guandu fault play a role in controlling the low velocity anomaly zone in middle basin. The depth extents of the two faults arc comparatively small, without traversing the interface of basin floor.