Seismological and Lithospheric Studies of the Libya Region

摘要

This report constitutes an integrated geophysical investigation of the lithospheric structure in the region of Libya. I' is separated into five sections. The final four sections represent papers that will be submitted to different scientific journals for publication. In the first part of the study, we utilized a seamless mosaicking approach based on the commercial Environment for Visualizing Images (ENVI) software package to create mosaics of two geologically interesting portions of Libya. For the second portion of the research, we made use of over 6,000 free air corrected gravity data in conjunction with other geological and geophysical data to develop a 3D density model for northern Libya. We then used the Nafe-Drake relationship along with other geological data to convert the 3D density model to a 3D velocity model (LIBYA3D) for the region. Two earthquakes having source receiver paths sampling much of the modeled area were used to perform ID and 1.5D validation tests, and the results were compared to those from previous studies. In the final part of this report, we utilize a 3-D geophysical model, 'LIBYA3D,' in the context of regional discrimination to investigate small to moderate size natural events (mb 3.7 - 5.7) in the Libyan region occurring from May 1990 to May 2000. Observations of Pn and Sn energy at varying frequency ranges (0.5 - 8 Hz) and propagation paths recorded by broadband instrumentation led us to investigate the attenuation affects of the geologic structure of the Libyan region and the adjacent Mediterranean Sea.