Interpretation of Lithospheric Images beneath China from P- and S-Wave Tomography
Abstract
High-resolution images of the lithosphere beneath Chinese continent have been obtained through body-wave tomography exploiting the arrival times of both P and S waves. We have used high quality first arrivals extracted from the Annual Bulletin of Chinese Earthquakes (ABCE). Totally 345,000 P wave, and 230,000 shear wave arrivals were used. We first obtained 2338 five-layer 1-D models from a Monte-Carlo random search (Sun et al., 2004) with a 1° x 1° (latitude, longitude) interval. After combining and smoothing the 1-D models, we generated an equivalent 3-D model as the starting model for tomographic study. Finally we modified the tomographic method (Zhao, 1991) to perform the 3D P and S tomography with both the Conrad and the Moho discontinuities as well as sediment layer included. Both horizontal and vertical resolutions are highly controlled and smooth transitions among adjacent locations are guaranteed in the final models. The models have good correlation with tectonic features and the predicted travel times through the 3-D model matched well with the observed ones at local and regional distances. To validate both P and S velocity models we generated synthetic seismograms and test their agreement with observed ones. We use four events with M5.0 to M6.0, occurring between 2001 and 2003, in different areas of China. Each event is recorded by up to 47 broadband stations in the China Digital Seismic Network (CDSN). For each event, we select waveforms recorded in the stations at different azimuths and at distances ranging from 50 km to 1000 km. We use the discrete wavenumber method (Bouchon, 2003) and finite difference modeling to generate seismograms between the source and the station. Both body waves and surface waves fit well in eastern, northern and southeastern China. Our tomographic models provide new insights into the geological structure and tectonics of the region, such as lithological variations and large fault zones across the major geological terranes. Compared with previous tomographic studies, we have used a larger, higher quality data set and applied a tomographic method to take into account the effects of the complex Conrad and Moho geometry and to include the sediment layers in this region. Our results cast a new light over the complex structure and seismotectonics of China and surrounding areas.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2005
- Bibcode:
- 2005AGUSM.S41A..02S
- Keywords:
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- 7200 SEISMOLOGY;
- 7230 Seismicity and seismotectonics;
- 7260 Theory and modeling