Accession Number : ADA323818

Title :   Investigation of Lg Blockage and the Transportability of Regional Discriminants in the Middle East.

Descriptive Note : Scientific rept. no. 1,

Corporate Author : ENSCO INC SPRINGFIELD VA

Personal Author(s) : Baumgardt, Douglas

PDF Url : ADA323818

Report Date : NOV 1996

Pagination or Media Count : 85

Abstract : To investigate nuclear explosion monitoring in the Middle East, the characteristics of regional phase propagation and regional discriminants have been investigated for events and propagation paths in Israel, Jordan, Lebanon, Syria, Egypt, and Iran. Mostly earthquake recordings from stations in the Middle East, including Iranian Long Period Array (ILPA) and Mednet and IRIS stations, have been studied with the goal of relating regional characterization of events in the Middle East to discrimination in the region. Pg and Lg propagation blockages have been noted for paths crossing the Levantine Basin of the Eastern Mediterranean and the Southern Caspian Basin north of Iran. However, Pn and Sn phases are often well observed for these paths which suggests that there may be a shear wave energy balance for seismic events which is conserved. Examples of attenuated Sn have been observed for the Red Sea region and may be correlated with high heat flow in this region. Analysis of Zagros thrust events in Iran recorded at two stations show significant variations in Pn/Lg ratios that may either be caused by propagation or source radiation pattern effects. Comparison of regional P/S ratios for Middle East earthquake with those in other regions shows that Pn/Sn and Pn/Lg ratios are interchangeable as discriminant features and usually can discriminate Middle Eastern earthquakes from mine blasts and nuclear explosions in other regions of Eurasia. Future studies should address the regional tectonic effects on regional discriminants to support interregional comparisons with explosions outside the Middle East, since it is unlikely the calibration explosions will be forthcoming within the Middle East.

Descriptors :   *SEISMIC DISCRIMINATION, MIDDLE EAST, COMPARISON, ATTENUATION, NUCLEAR EXPLOSION DETECTION, EARTHQUAKES, BASINS(GEOGRAPHIC).

Subject Categories : Seismic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE