HR: 1330h
AN: S22A-0413    [PDF]
TI: More Evidence for Strong Lithospheric Mantle: Mantle Earthquakes in Zambia
AU: * Yang, Z
EM: zyang1@uiuc.edu
AF: Dept. of Geology, Univ. of Illinois, Urbana, IL 61801 United States
AU: Chen, W
EM: wpchen@uiuc.edu
AF: Dept. of Geology, Univ. of Illinois, Urbana, IL 61801 United States
AB: The occurrence of intra-continental earthquakes in the mantle is a key evidence for strong mantle lithosphere. To this end, the most direct way to establish if intra-continental earthquakes occur in the mantle is to determine focal depths RELATIVE to the Moho. This approach bypasses the need for precise knowledge of both focal depths and local crustal thickness in the source region -- often difficult requirements to meet simultaneously. We report preliminary results using underside reflections off the Moho directly above the source to ascertain that mantle earthquakes do occur away from the East African rift in Zambia. By matching observed, teleseismic P-waveforms with synthetic seismograms, we identified underside reflections off the Moho (pmP phase) based on its polarity and timing relative to the direct arrival, thus confirming the occurrence of mantle seismicity regardless of the actual crustal thickness in Zambia. By focusing on longstanding, quite receiver sites and on dense arrays, we are currently gathering a set of pmP data with short source-time functions and of exceptionally high signal-to-noise ratios. (Supported by NSF Continental Dynamics Program: Project Hi-CLIMB.)
DE: 7215 Earthquake parameters
DE: 7218 Lithosphere and upper mantle
DE: 8109 Continental tectonics--extensional (0905)
DE: 8159 Rheology--crust and lithosphere
DE: 8162 Rheology--mantle
SC: Seismology [S]
MN: 2003 Fall Meeting