Lithospheric seismic structure of the eastern region of the Arabian Peninsula

The lithospheric structure of the eastern region of the Arabian Peninsula h as been derived using the spectral analysis of intermediate period P-wave a mplitude ratios. Sixteen earthquakes recorded at the intermediate 3-compone nt DHR station during the period from 1986 to 1995 were selected for analys is based on the following criteria: focal depths with a range between 15 an d 300 km, body-wave magnitudes greater than 5.0, epicentral distances with a range from 13 degrees to 82 degrees. By comparing the spectral peak positions of the observed and theoretical va lues, the thickness and velocity can be resolved within 3 km and 0.3 km s(- 1), respectively of the observed values. Earthquakes from the Eurasian plat e, Japan and China show high cross-correlation ratios (>85%) and events fro m the Arabian plate, gulf of Aqabah, Red and Mediterranean Seas indicate cr oss-correlation ratios between 60-84%. The derived crustal model is not unique due to the theoretical assumptions (horizontal layering, constant densities and velocities in each layer), qua lity of the data and complexities of the crustal structure. The model sugge sts that the crust consists of five distinct layers with a strong velocity gradient of about 0.05 km s(-1) km(-1) in the upper crust and 0.03 km s(-1) km(-1) in the lower crust. The average results for several observations gi ve a crustal thickness of 51 km and, a mean P-wave velocity of 6.2 km s(-1) . Depth to the crystalline basement is approximately 8 km which is in good agreement with values obtained by some oil wells in the eastern region. The Mohorovicic discontinuity indicates a velocity of 8.3 km s(-1) of the uppe r mantle and 51 km depth. (C) 1999 Elsevier Science Ltd. All rights reserve d.