| Popis: |
Understanding the evolution of the continental lithosphere requires improving our knowledge on lower continental composition. Towards this goal, we perform receiver function analysis using teleseismic waveforms recorded at permanent and temporary broadband seismic stations located in Middle East, Europe, Asia, and North Africa. Two hundred and twenty six stations recording a total of about 6,000 teleseismic events producing more than 100,000 seismograms have been investigated. We have examined receiver functions for 213 of stations (best data) in the period of 1990 - 2004 and applied the receiver function stacking procedure of Zhuand Kanamori [2000] to estimate Poisson's ratio and crustal thickness. We have divided the research area according to five tectonics environments, explicitly Shields, Platform, Paleozoic orogenic belts, MesozoicCenozoic orogenic belts, and rift zones based on Condie's [1989] simplified classifications. The results from this study shows lower value of Poisson's ratio sigma = 0.25 for Shield and Platform compare to the Orogenic belts with sigma = 0.27. Crustal thickness for Shield and Platform show the value of 38 km and 43 km respectively, while for the Orogenic belts we found a value of 37 km for Paleozoic belts and 39 km for Mesozoic-Cenozoic belts, although the range of thicknesses for the younger active regions is large. Since our ultimate goal is to provide an improved imaged of global continental structure and composition, we combine our observations with receiver functions results from other published analysis. In total we have integrated observations from 374 stations located in different geologic setting and the results indicate the value of sigma = 0.26 for Poisson's ratio and H = 38 km for crustal thickness in Shield, sigma = 0.27 with H = 43 km for the Platform and sigma + 0.28 with H = 36-39 km for the Orogenic belts. |
