Structural Architecture and Active Deformation of the Makkah-Madinah Transform Zone, Western Arabia

In the western Arabia margin, a complex continental shearing system named Makkah-Madinah Transform Zone (MMTZ) is documented, in part, by an echelon of alkalic volcanic ridge of scoria cones segmented by structural step-overs. We investigate the MMTZ structural architecture and kinematics via field observations, remote sensing, potential field data, structural analysis of the fracture patterns, and moment tensor solutions of recorded earthquakes. As reported earlier, the southern MMTZ is segmented by several major dextral faults correlated with significant structural step-overs between volcanic cones lineaments in Harrat Rahat and in between Harrats Rahat and Khaybar. We report another major dextral fault between Harrats Khaybar and Ithnayn, which follows the same step-overs pattern reported within Harrat Rahat. To validate the observed structure, we map the recorded earthquakes over the transitions between Harrats Rahat-Khaybar and Khaybar-Ithnayn, moment tensor solutions for earthquakes larger than 3 Mw as the focal mechanisms map affirm the observed structural patterns between Harrats Khaybar and Ithnayn and inferred structures between the MMTZ and Red Sea (RS). We infer the maximum horizontal stress direction from the MMTZ structural architecture that is parallel to the central RS transforms. Hence, we build thermomechanical model along the maximum horizontal stress direction to investigate the implications of the MMTZ and RS coevality. We show that potential rifting migration from the MMTZ to the RS along the maximum horizontal stress direction is controlled by lithospheric strength, inherited weakness, and regional boundary conditions.