HR: 14:25h
AN: T23F-04 INVITED    [Abstracts]
TI: Surface Wave Dispersion Measurements and Tomography from Ambient Seismic Noise in China
AU: * Song, X
EM: xsong@uiuc.edu
AF: Department of Geology, University of Illinois, Urbana, IL 61801, United States
AU: Zheng, S
EM: shzheng@uiuc.edu
AF: Department of Geology, University of Illinois, Urbana, IL 61801, United States
AU: Zheng, S
EM: shzheng@uiuc.edu
AF: Institute of Earthquake Science, China Earthquake Administration, Beijing, 100036, China
AU: Sun, X
EM: xsun@uiuc.edu
AF: Department of Geology, University of Illinois, Urbana, IL 61801, United States
AU: Ritzwoller, M H
EM: ritzwoll@anquetil.colorado.edu
AF: Department of Physics, University of Colorado at Boulder, Boulder, CO 80309, United States
AU: Yang, Y
EM: Yingjie.Yang@colorado.edu
AF: Department of Physics, University of Colorado at Boulder, Boulder, CO 80309, United States
AB: Recent laboratory and theoretical studies have shown that the Green functions of a structure can be obtained from the cross-correlation of diffuse wavefields. The idea has now found rapid applications in seismology, in particular, surface waves have been found to be most easily retrievable from the cross-correlations of seismic coda or ambient noise. Dispersion measurements made on the estimated Green functions present significant advantages over traditional measurements that are based on earthquakes with limited distribution. The method is particularly useful in surface-wave path calibration and tomographic mapping in aseismic regions and at short periods (below 20 s). We have recently performed ambient noise tomography of China using the new national China Seismic Network and surrounding global and regional stations. For most station pairs, we can retrieve very good Rayleigh waves from ambient noise correlations using 12-months of continuous data at all distance ranges (100 km to 5000 km) and for periods down to about 8 s. The combination of stations achieves good and relatively uniform coverage for most parts of China. We obtain Rayleigh wave group velocity dispersion measurements (a total of about 1400 dispersion curves so far) using a frequency-time analysis method and construct Rayleigh wave group velocity maps for periods from 10 s to 60 s. Our preliminary dispersion maps show significant features that correlate with surface geology. Two major features stand out in particular. First, the major basins with thick sediment deposition correlate well with slow group velocities at shorter periods (10 to 20 s). The major basins, including Tarim, Junggar, Qadaim, Sichuan, Bohai, Songliao, Southern North China, and Jianghan, are all well delineated by slow velocities. Second, variations in crustal thickness correlate with group velocities for periods around 30 s. The major trend of crust thickening from the east to west is well represented by the velocity decreases from east to west.
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting