Investigations of Libyan Upper Mantle Anisotropy and Crustal Structure Using Shear Wave Splitting and Receiver Function Analyses

Abstract

Here we report an analysis of data obtained from 15 stations belonging to the Libyan Seismic Network in addition to 5 publically available stations both in Libya and adjacent areas by employing both shear-wave splitting and receiver function methods. A total of 583 pairs of high-quality SWS measurements utilizing PKS, SKKS, and SKS phases from 20 broadband stations demonstrate primarily NNE-SSW to NNW-SSE fast orientations. An absence of significant fast direction variation as a function of event back-azimuth indicates the presence of simple anisotropy. Lack of correlation between surficial features and the observed fast orientations suggests that the origin of the anisotropy is asthenospheric. Preliminary time-series stacking of about 1000 radial RFs indicates that the crust does not thin significantly from the continental margin, where the crustal thickness ranges from 30 to 35 km, to inland Libya where the crust is about 30 km thick excepting local thickening due to volcanic activity. Measurements of the P-to-S wave velocity ratio Vp/Vs, which range from 1.70 to 1.87, reveal short-order variations as the result of heavy sedimentary basin deposits and local magmatic emplacement.

AAPG Datapages/Search and Discovery Article #90218 © 2015 Eastern Section Meeting, Indianapolis, Indiana, September 20-22, 2015