Accession Number : ADA317387

Title :   Seismic Attenuation Studies in the Middle East and Southern Asia.

Descriptive Note : Scientific rept. no. 1,

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

Personal Author(s) : Mitchell, Brian J. ; Cong, Lianli ; Xie, Jiakang

PDF Url : ADA317387

Report Date : 19 JUL 1996

Pagination or Media Count : 53

Abstract : Previous research has indicated that the Middle East and southern Asia are characterized by high attenuation that may be caused by high intrinsic absorption, scattering by complex velocity structure, or both. We are trying to model these attenuative properties by measuring the attenuation of Lg coda waves as well as fundamental-mode surface waves in that region. Determinations of Lg coda Q there have allowed us to complete our map of Lg coda Q for all of Eurasia. Initial determinations of fundamental-mode Rayleigh and Love wave attenuation, using a two-station method indicate that attenuation for those waves, especially at short periods, is very high. This suggests that Q in the upper crust is very low, a result that is consistent with our Lg coda Q results. A new code has been developed for measuring dispersion and polarization properties of surface waves. Initial tests with code indicate that surface wave propagation in the Middle East is often complex and marked by lateral refraction and mode conversion along the paths of propagation.

Descriptors :   *ATTENUATION, *SEISMOLOGY, MIDDLE EAST, WAVE PROPAGATION, EARTH CRUST, SEISMIC WAVES, Q FACTOR, SOUTH ASIA.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE