HR: 0800h
AN: T41A-1273    [Abstracts]
TI: Amplitude Tomography From ML-Magnitude Data Beneath China
AU: * Wang, S
EM: suyunw@163bj.com
AF: Geophysical union of China, Minzuxueyuan nanlu, Beijing, BJ 100081 China
AU: Hearn, T
EM: thearn@nmsu.edu
AF: American Geophysical union, 2000 Florida Avenue, Washington, DC 20009 United States
AU: Pei, S
EM: peisp@itpcas.ac.cn
AF: Geophysical union of China, Minzuxueyuan nanlu, Beijing, BJ 100081 China
AU: Xu, Z
EM: xuzh@cea-igp.ac.cn
AF: Geophysical union of China, Minzuxueyuan nanlu, Beijing, BJ 100081 China
AU: Ni, J
EM: jni@nmsu.edu
AF: American Geophysical union, 2000 Florida Avenue, Washington, DC 20009 United States
AU: Yu, Y
EM: yyx@cea-igp.ac.cn
AF: Geophysical union of China, Minzuxueyuan nanlu, Beijing, BJ 100081 China
AB: Using the data of S wave amplitude and period reported in the Annual Bulletin of Chinese Earthquakes(1984-2004) for the calculation of ML estimates, we studied the S wave attenuation in the crust and the regional variation of material quality factor Q. Over 54,000 S wave amplitudes were used to map regional attenuation beneath China. These amplitudes were measured from the horizontal components of short-period (about 0.1-2.0 seconds) instruments and generally correspond to regional S waves which propagate within the upper and middle crust. Data are corrected for event size and geometric spreading, but not for radiation pattern. Classical, two-dimensional tomography methods are adapted to find regional attenuation variations, site gain effects, and source size corrections. Features larger than 2 degrees are well resolved. The attenuation Q0 value for these data averages around 360 beneath China. The regional Q0 fluctuation varies from -200 to +200. Regions with the highest Q0 value (low attenuation) are beneath the Tarim Basin, Sichuan Basin, Ordos platform and the southeast China fold belt. Regions with the lowest Q0 value (high attenuation) are beneath Bohai Bay, the North China plain in eastern China and the Panxi rift along the eastern margin of the Tibet Plateau. In general, Q0 values in tectonically stable regions such as the cratonic platform tend to be high, while those in tectonically active regions tend to be low.
UR: http://www.cea-igp.ac.cn
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7270 Tomography (6982, 8180)
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: Fall Meeting 2005