An integrated geophysical study of the lithospheric structure beneath Libya

Wesley A Brown, University of Texas at El Paso

Abstract

This doctoral dissertation constitutes an integrated geophysical investigation of the lithospheric structure in the region of Libya. It is separated into three sections, each of which will be submitted to different scientific journals for publication. In the first part of the study, I 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. In this study I present a step by step method of mosaicking Landsat 4 satellite images. Firstly, I performed histogram matching to give images the same color scale, then I used a cutline feathering technique to blend suture areas and finally I overlaid the images to form the two mosaics. The resulting mosaics were then combined with structural features and the seismicity map of the area. The resulting mosaics were proven to be useful in identifying recently active faults and shows great potential for verification of other faults and in natural hazard assessment. ^ For the second portion of my research, I 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. I used a gravity modeling program (SURFGRAV) to develop the 3D density model by manipulating it to accurately predict large areas of Free Air anomaly shown in the data. The residual gravity anomaly values were calculated by subtracting predicted Free Air anomaly from the observed Free Air anomaly. The results were satisfactory for uplifted areas of Libya while there were significant mismatches in basin areas. The density model was iterated and used as a starting model for the final portion of the study. ^ In the last part of this research, I 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 1D and 1.5D validation tests, and the results were compared to those from previous studies. The results showed that the new 3D velocity model is valid and superior to the global model. However, until there is sufficient earthquake data acquired, and we are able to perform 2D and 3D modeling we may not be able to see the true improvement of LIBYA3D as compared to the other regional models. ^

Subject Area

Geodesy|Geology|Geophysics

Recommended Citation

Brown, Wesley A, "An integrated geophysical study of the lithospheric structure beneath Libya" (2004). ETD Collection for University of Texas, El Paso. AAI3158433.
http://digitalcommons.utep.edu/dissertations/AAI3158433

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