Seismic structure beneath the Gulf of Aqaba and adjacent areas based on the tomographic inversion of regional earthquake data

Sami El Khrepy,Alexey G Petrunin,Ivan Koulakov,Nassir Al-Arifi

doi:10.5194/se-7-965-2016

Abstract

Abstract. We present the first 3-D model of seismic P and S velocities in the crust and uppermost mantle beneath the Gulf of Aqaba and surrounding areas based on the results of passive travel time tomography. The tomographic inversion was performed based on travel time data from ∼ 9000 regional earthquakes provided by the Egyptian National Seismological Network (ENSN), and this was complemented with data from the International Seismological Centre (ISC). The resulting P and S velocity patterns were generally consistent with each other at all depths. Beneath the northern part of the Red Sea, we observed a strong high-velocity anomaly with abrupt limits that coincide with the coastal lines. This finding may indicate the oceanic nature of the crust in the Red Sea, and it does not support the concept of gradual stretching of the continental crust. According to our results, in the middle and lower crust, the seismic anomalies beneath the Gulf of Aqaba seem to delineate a sinistral shift (∼ 100 km) in the opposite flanks of the fault zone, which is consistent with other estimates of the left-lateral displacement in the southern part of the Dead Sea Transform fault. However, no displacement structures were visible in the uppermost lithospheric mantle.

Highlights

Tectonic activity in the Gulf of Aqaba region is responsible for high levels of seismicity, which represent a significant hazard for the local population
The purpose of this study is to close this gap and to present a new tomographic model based on a large dataset, which was provided by the Egyptian National Seismological Network (ENSN) and complemented with data from the International Seismological Centre (ISC)
Before discussing the main velocity models, we present the results of synthetic tests used to assess the horizontal and vertical resolution

Summary

Introduction

Tectonic activity in the Gulf of Aqaba region is responsible for high levels of seismicity, which represent a significant hazard for the local population. One of the issues relates to the nature of the opening of the Red Sea northern segment. It is still unclear whether this feature results from stretching of the continental crust or from spreading and formation of the ocean-type crust. Several other unanswered questions relate to the mechanisms of origin and evolution of the Dead Sea Transform (DST) fault. It is still debated which portion of the lithosphere (only the crust or the entire lithosphere) is involved in the strikeslip displacement along this fault zone. There are several alternative hypotheses related to the opening of the deep basins of Aqaba and the Dead Sea along the fault zone

Objectives

Results

Discussion

Conclusion