HR: 0800h
AN: T11C-1275    [Abstracts]
TI: Crustal velocity structure in the Changbaishan volcanic area, NE China, determined from a wide-angle refraction/reflection experiment and a temporary broadband array
AU: Song, J
EM: jsong@usgs.gov
AF: U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543 United States
AU: * Hetland, E A
EM: eah@mit.edu
AF: Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambrige, MA 02139 United States
AU: Wu, F T
EM: francis@binghamton.edu
AF: SUNY Binghamton, Vestal Parkway E, Binghamton, NY 13902 United States
AU: Zhang, C
AF: Research Center for Exploration Geophysics, China Seismological Bureau, Zhengzhou, 450002 China
AB: The Changbaishan volcanic region, located along the border between China and North Korea, has had several large eruptions in the past few thousand years. However there has been little volcanic activity for several hundred years. So far studies of this active volcanic group have been limited and have not been widely published. In the summer of 1998, the State University of New York at Binghamton, in collaboration with the Research Center of Exploration Geophysics (RCEG) of the Chinese Seismological Bureau, installed 19 portable, broadband seismic stations on the Chinese side of the region of the Changbaishan. The broadband stations were borrowed from IRIS/PASSCAL, installed in June 1998, and were in operation for 3--8 months. During that summer, the RCEG conducted a wide-angle experiment. The active source experiment consisted of two primary lines and several shots and receivers distributed over the region. One of the primary lines trended north-south across the Tianchi volcano (the main volcanic edifice in the area), while the other trended east-west to the north of the Tianchi. We estimated crustal velocities by modeling receiver functions derived from seismograms collected at the broadband network as well as inversion of the travel-times from the wide-angle experiment. Both results resolved a low-velocity zone (LVZ) in the upper crust (below about 5--10 km depths) to the north of the Tianchi volcano and a 5--10 km thickening of the crust under the Tianchi. This LVZ is defined by sharp velocity gradients and velocities that are at most 0.8 km/sec below the surrounding crust. The LVZ is approximately 10--15 km thick and is likely 5--20$\times 10^3$ km$^2$. The nature of the LVZ can be explored in view of the previous geophysical and geochemical studies of this area.
DE: 7280 Volcano seismology (8419)
DE: 7299 General or miscellaneous
DE: 7205 Continental crust (1242)
DE: 0999 General or miscellaneous
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting