HR: 1330h
AN: S22A-0415    [PDF]
TI: Pn inversion of the Tibetan Plateau from regional networks and INDEPTH experiments
AU: Liang, C
EM: liang4@uiuc.edu
AF: Geology Department, University of Illinois at Urbana Champaign, 1301 West Green, NHB127, Urbana, IL 61801 United States
AU: * Song, X
EM: xsong@uiuc.edu
AF: Geology Department, University of Illinois at Urbana Champaign, 1301 West Green, NHB127, Urbana, IL 61801 United States
AB: We perform an inversion of Pn travel times from the Chinese earthquake bulletins and the ISC bulletins as well as hand picks of the data from INDEPTH experiments and other digital stations. We invert for Pn velocity and anisotropy as well as station delays (which reflect primarily Moho depth variations). The use of the Chinese provincial and national stations increases the data coverage by an order of magnitude compared with previous studies. The inclusion of INDEPTH stations and Chinese stations in Tibet increases the azimuthal coverage of ray paths and allows us to examine crustal thickness variation across the plateau. Our results suggest that the Pn velocity in the northern Tibet is generally lower than in southern Tibet, consistent with previous studies. However, our model suggests a more complex structure. The low velocity anomalies can be traced from the northern Tibet across southwestern Tibet and south central Tibet to the India plate. Significantly, nearly all the reported intermediate depth, subcrustal earthquakes in the region in our areas of high Pn velocity in southern Tibet, western Kunlun or Pamir. This suggests that these high Pn velocity regions are cold enough to support brittle failure. Although limited by the number of subcrustal earthquakes, the result suggests that Pn velocity could be an excellent indicator of mantle lithosphere strength. Our preliminary results also suggest a significant change in crustal thickness and Pn anisotropy across the Banggong-Nujiang suture, which correlates with the observed changes in gravity anomaly and SKS splitting across the boundary.
DE: 0905 Continental structures (8109, 8110)
DE: 0935 Seismic methods (3025)
DE: 7205 Continental crust (1242)
DE: 8180 Tomography
DE: 9320 Asia
SC: Seismology [S]
MN: 2003 Fall Meeting