Accession Number : ADA320418

Title :   Synthetic and Observational Study of Pn Excitation and Propagation in Central Asia.

Descriptive Note : Scientific rept. no. 1,

Corporate Author : SAINT LOUIS UNIV MO DEPT OF EARTH AND ATMOSPHERIC SCIENCES

Personal Author(s) : Xie, Jiakang

PDF Url : ADA320418

Report Date : 15 OCT 1996

Pagination or Media Count : 36

Abstract : More than one hundred Pn spectra from central Asia have been collected. The nonlinear spectral inversion method of Xie (1993) was modified to reduce effects of deviations of sources, paths and sites from idealized theoretical models. To estimate Pn geometrical spreading, synthetic calculations of Pn propagation in central Asia were conducted using 1D velocity models. The results show that the model is roughly valid, but deviations in Pn amplitude from that model can be a factor of 2. The observed Pn amplitude in central Asia are strongly affected by 3D structural complications and source radiation patterns. Pn amplitude across the Kyrghistan network (KNET) from sources located in and around the Lop Nor Test Site is highly variable (by a factor of about 20), despite the small aperture of the KNET (approximately 2 degrees). The amplitude variation is not due to a systematic variation in site responses, but is likely due to deep-seated 3D structural complications, such as a complex Moho topography. Pn amplitudes across KNET from some Northern Xinjiang earthquakes are much weaker than from the Lop Nor explosions, making Pn/Lg ratio an effective discriminant. The performance of the discriminant varies with varying focal mechanisms and path configurations.

Descriptors :   *SEISMIC DISCRIMINATION, *EARTHQUAKES, EXCITATION, UNDERGROUND EXPLOSIONS, SEISMIC DATA, NONLINEAR SYSTEMS, ASIA, STRUCTURAL GEOLOGY, PRIMARY WAVES(SEISMIC WAVES), EARTH MANTLE, SEISMOLOGICAL STATIONS.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE