[J08-P] Poster

[J08-P-18] The 3-D velocity structure of the 2008 Taoyuan Earthquake Sequence in Kaohsiung, Taiwan

^○Min Hung Shih, Bor-Shouh Huang (Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan)

The three-dimensional velocity structure of the upper crust was determined by using the arrival readings were identified from the 2008 Taoyuan Earthquake Sequence. On March 4, 2008, a moderate earthquake (ML 5.2) occurred in Taoyuan district of Kaohsiung City in southern Taiwan. It was followed by numerous aftershocks in the next 48 hours, including three events with magnitude larger than 4. The high-resolution waveform data of this sequence were well-recorded by a large number of recording stations. These stations belong to several different permanent networks (operated by IES, NCU, and NCCU) and temporary networks (deployed by TAIGER project, Taiwan Integrated Geodynamic Research project) all around Taiwan. All waveform data are managed and processed by Antelope software suite. We applied a 1-D velocity model for locating events in the preliminary analysis. In this study, we introduced the double-difference tomography method not only to determine the fault geometry of the main shock but also to investigate the detailed 3-D velocity structure in this area. The results indicate that aftershocks are extended along the NE-SW direction and located on a 45 SE-dipping plane, which agrees with one of the nodal planes of Global CMT solution (strike = 45, dip = 40, and rake = 119). We can identify a clear low-velocity area which is enclosed by events next to the main shock in the final 3D velocity model. We also recognized a 45 degree-dipping zone, which is extended to the ground surface with low-velocity; meanwhile, velocity structure variation in study area corresponds to major geologic units in Taiwan.