Structure of the Yanbu suture zone in Northwest Saudi Arabia inferred from aeromagnetic and seismological data

Abstract

The present work focuses on a study of the Yanbu suture zone and related ophiolites using aeromagnetic and seismological data. The interpretation of aeromagnetic data indicates that NW–SE- and NE–SW-trending structural faults dominate the study area. These faults coincide with narrow and elongated magnetic highs, possibly caused by intrusions emplaced along the faults. The NE trend is dissected by cross-cutting NW-trending faults in some places. The NE-oriented suture zone is marked by short-wavelength high magnetic anomalies associated with ultramafic rocks (ophiolites) and is divided by the NW-oriented left-lateral Najid faulting (Qazaz shear zone) into two shifted alignments. This implies that deep-seated regional trends govern to a large extent the location and extension of the ophiolite exposures. There is a clear correlation between land earthquakes and the interpreted magnetic structures, where the majority of earthquake epicenters lie on or close to the interpreted major faults. A clear concentration of earthquakes is observed where the NE-trending faults cross the Red Sea NNW-trending faults. Here, two separate aftershock clusters occur to the north of Yanbu City, indicating the reactivation of the pre-existing Precambrian NE-trending transform fault,which crosses two parallel NNW-trending faults that have been injected by Cenozoic volcanics during the Cenozoic rifting of the Red Sea. These results indicate that the seismotectonics of the study area is strongly related to the geodynamic rifting processes acting in the Red Sea, where the relative movement between African and Arabian plates resulted in several series of normal and transform faults that run parallel and cross the Red Sea, respectively.