Ambient Noise Tomography of the Saudi Arabian Shield

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

Saudi Arabia is located in a tectonically active region: spreading occurs to the west and south in the Red Sea rift and the Gulf of Aden and is accommodated by a fold and thrust belt in the Zagros mountains to the north-east. The geology in western Saudi Arabia is primarily dominated by the Arabian Shield, a ~725,000 km^2 surface expression of Precambrian rock, which is locally covered by Cenozoic basaltic lava called “harrats”. In 2009, an earthquake swarm caused by a dike intrusion at Harrat Lunayirr prompted the need of new hazard models for this region.

Reliable high-resolution shear-wave crustal velocity models provide critical information about the composition and other physical properties of the crust and are required to accurately assess seismic hazards. We used surface waves generated by ambient seismic noise to develop surface-wave dispersion maps and a pseudo-3D shear-wave velocity model for the Arabian Shield. Teleseismic P-waves are detected in the ambient noise records, and their detection is attributed to the lack of attenuation in the Arabian Shield. Rayleigh and Love dispersion maps show low crustal surface-wave velocities (on the order of -5%) in the northern harrats (> 24° N).

Each node in the dispersion maps (size 0.2° x 0.2°) was inverted to shear-velocity using the Neighborhood Algorithm and an input model based on the results of a country-wide refraction survey. We found low shear-velocities in both the upper and lower crust co-located with the northern harrats but only in the lower crust for the southern harrats.

Presenting Author: Francesco Civilini

Authors