Dike Intrusions and Magma Accumulation in the Red Sea Region: Insights from InSAR and High-Resolution Optical Imagery

Abstract:

During the past decade, several magmatic intrusions and eruptions have occurred in the Red Sea region. The activity began in 2007 with an eruption on Jebel at Tair Island and it was the first volcanic event known to occur in the southern Red Sea in over a century. We used co-eruption InSAR data to constrain a tensile dislocation model, which suggests that the island’s stress field is both temporarily varying and isolated from the regional Red Sea stress regime. Later in 2009, a dike intrusion in Harrat Lunayyir (western Saudi Arabia) almost made it to the surface to start an eruption. Our InSAR observations document how the intrusion first ascended to shallow depths and then started activating graben-bounding normal faults. The progressive dike opening resulted in over a meter of crustal extension and extensive surface fracturing. During the post-diking period, the ground deformation continued, but was of an order of magnitude smaller than the displacements associated with the main event. More recently, two Surtseyan eruptions occurred in the Zubair archipelago (southern Red Sea) forming two new islands in 2011-12 and 2013. High-resolution optical imagery reveals that significant wind and coastal erosion rapidly changed both the size and the shape of the two new islands during the months following the end of the eruptions. Several TanDEM-X InSAR data sets show the co-eruption deformation that occurred on the neighboring islands, indicating that both eruptions were fed by two ~10 km long dikes with a thickness of ~1 m. All these volcanic events were fed by dike intrusions and were contemporaneously associated with significant seismic swarms. Our observations do not show evidence for shallow magma reservoirs at these locations and that the magma appears to have ascended directly from a significant depth.