Broadband Seismic Experiment in Yunnan, Southwest China

摘要

A broadband portable seismic network has been deployed in Yunnan, southwest China, to collect seismic data for advanced studies on regional crustal and mantle structures, earthquake prediction, and regional characteristics of wave propagation and seismic sources. The region in southwest China is situated in an evolving tectonic region transitioning between the uplifted Tibetan plateau to the west and the Yangtze continental platform to the east. The region displays varying crustal thickness from 35 km to over 60 km with seismic activity strongly associated with the locally mapped active faults. The temporary seismic network, consisting of 25 portable broadband and narrow-band seismic stations, is deployed in the region of 98 deg. E-105 deg. E, 21 deg. N-29 deg. N. There are also 23 permanent digital broadband seismic stations recording in the region. Yunnan has the strongest intra-plate seismic activities in China. Moreover, there are several strong seismic zones in its surrounding areas, such as Tibet, Sichuan, Burma, and India. The strong seismicity in Yunnan and its surrounding areas provides the foundation for success of this deployment. Preliminary analyses have yielded an enhanced ground truth database, a 3-D structure model (together with some other analyses) for improving location, and characteristic spectral ratios for different events. Moreover, analysis of the recordings of some events of special interest, such as the January 26, 2001, M7.7 India earthquake and the February 14, 2001, M5.0 Yajiang, Sichuan, earthquake, has provided useful information on the source, path, and site effect, that are important for regional seismic studies.