Crustal structure of the Arabian Plate: New constraints from the analysis of teleseismic receiver functions

Receiver function for teleseismic earthquakes recorded at 23 broadband and mid-band stations in Saudi Arabia and Jordan were processed to map variations in crustal thickness. The receiver functions were stacked using a slant-staking technique to estimate the Moho depth and the Vp/Vs for each station. The errors in the slant stacking were estimated using a bootstrap error technique. The grid search technique was also used to estimate the crustal structure for seven stations. A jackknife error estimation method was used to estimate the errors in the grid search results for three stations. The average crustal thickness of the Arabian shield is 39 km. The crust thins to about 23 km along the Red Sea and to about 29 km along the Gulf of Aqaba. In the northern part of the platform, the crust varies from 33 - 37 km. This is less than the average crust in the shield. However, the crust is thicker (41 - 49 km) in the southern part of the platform. Our Moho map shows a dramatic change in crustal thickness between the topographic escarpment of the Arabian shield and the shorelines of the Red Sea. The Moho depth in the Proterozoic Arabian shield is relatively stable, and ranges between 35 - 45 km with an average of 39 km. We compared our results in the shield to nine Proterozoic and Archean shields regions that include reasonably well-determined Moho depths. Overall, we do not observe significant difference between Proterozoic and Archean crustal thickness. We observed a dramatic change in crustal thickness along the Red Sea margin that occurred over a relatively short distance. The transition from oceanic to continental crust along the Red Sea margin occurs in < 250 km, while the transition in a typical west Atlantic-type margin occurs in over 450 km. This important result highlights the abruptness of the breakup of Arabia. We argue that a preexisting zone of weakness coupled with anomalously hot upper mantle could have initiated and expedited the breakup.