Accession Number : ADA318990

Title :   An Integrated Study of Lithospheric Structure, Regional Seismic Wave Propagation, and Seismic Discrimination Capability in the Middle East.

Descriptive Note : Scientific rept. no. 1,

Corporate Author : CAMBRIDGE UNIV (UNITED KINGDOM) DEPT OF EARTH SCIENCES

Personal Author(s) : Priestley, Keith

PDF Url : ADA318990

Report Date : 07 OCT 1996

Pagination or Media Count : 127

Abstract : The upper mantle compressional wave velocity beneath the Iranian Plateau is determined by measuring two station interval velocities from first arrivals in the distance range 2 to 18 degrees reported in the ISC. The Pn velocity is near 8.1 km/s beneath the Zagros Mts. and most of the northern part of the plateau. A lower Pn velocity of about 7.8 km/s occur beneath NW Iran. Additional Pn velocity estimates are made using recordings of well located aftershocks, and these confirm the two station Pn velocity measurements. A new 1-D earth model for the crust and upper mantle beneath the Archaean core of southern Africa is determined. Below the 42-km thick crust there is an 80-km thick upper mantle lid. Vp and Vs are 8.09 and 4.62 km/s, respectively, at the top of the lid and the compressional and shear velocity gradients through the lid are 0.0008/s and 0.0013/s, respectively. Below the lid there is a substantial shear wave LVZ. Velocities and densities in the seismic model of the lid closely agree with velocity and density estimates from geochemical analysis of garnet peridotite nodules from kimberlites on the Kaapvaal Craton, implying that the estimates from kimberlites are representative of a wider region of the Archaean core of southern Africa.

Descriptors :   *SEISMIC WAVES, *SEISMIC DISCRIMINATION, *EARTH MANTLE, SUBSAHARAN AFRICA, GROUND SHOCK, SEISMIC DATA, WAVE PROPAGATION, EARTH CRUST, EARTHQUAKES, EARTH MODELS, PLATE TECTONICS, SEISMIC VELOCITY, GEOCHEMISTRY, IRAN, STRUCTURAL GEOLOGY, PRIMARY WAVES(SEISMIC WAVES), SECONDARY WAVES, SEISMOGRAPHS, LITHOSPHERE, GEOLOGIC MODELS.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE