Integrated seismic exploration in the collision plate boundary of Taiwan

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We deployed 60 3-component seismographs along a 150-km-long line in the southern part of Taiwan to observe natural earthquakes in 2005. We have recorded local, regional and teleseismic events. The data show large-scale deformation of the crust, which might be controlled by the collision tectonics in Taiwan. A highly active seismic activity was detected in central part of the east-west line indicating intra seicmic activity.We analyzed the seismic data that we acquired in 2005 to obtain a two-dimensional seismic velocity structure under the east-west line. The tomogram that we obtained shows a thick crust beneath the central mountains and a high velocity body intruding to a shallower part of the crust.We integrated the data form the observation of aftershocks of the 1999 Chi-Chi earthquake, those of the 2001 observation in Taiwan, and other geophysical data, which are collected to plan the TAIGER project proposed by the US and Taiwan scientists. We discussed the results in the TAIGER work shop held in Taiwan.The integrated results indicate that the whole lithospheric collision tectonics is, at least the central and southern part of Taiwan mountain areas, important to understand the mountain building process. The collision tectonics has important implication to the Japanese in-land earthquakes such as the 2004 mid-Niigata prefecture earthquake. We compared earthquakes and tectonics in Taiwan and Japan.