InSAR Observations of Ground Deformation in Arabia
Jónsson, Sigurjón; Xu, Wenbin; Akoglu, Ahmet; Smith, Robert; Wang, Teng; Feng, Guangcai; Speth, Kasper; Abdullin, Ayrat
King Abdullah University of Science and Technology (KAUST), SAUDI ARABIA
The Arabian plate is surrounded by a variety of active plate boundaries, with extension in the Red Sea and Gulf of Aden to the south, compression in Turkey and Iran to the north, and transform-motion across faults to the west and to the east. Internally, however, the Arabian plate has been shown to be tectonically rather stable, despite evidence of recent volcanism and earthquake faults.
Among recent major earthquakes that have occurred on the Arabian plate boundary are the magnitude 7.3 Gulf of Aqaba earthquake in 1995 and the magnitude 7.1 Van earthquake in eastern Turkey in 2011. The Gulf of Aqaba earthquake occurred between the Arabian plate and the Sinai block, near the southern end of the Dead Sea transform. It was primarily a transform-faulting earthquake and took place mostly offshore, although significant surface faulting was found on the Saudi coast. The Van earthquake occurred as a result of convergence of the Arabian plate towards Eurasia and happened on northward dipping reverse fault, which we constrained using coseismic Cosmo-Skymed, Envisat, GPS, and coastal uplift data.
The recently discovered Qadimah fault is located on the Red Sea coast north of Jeddah and runs through King Abdullah Economic City, a planned $50 billion harbor city. This normal fault is parallel to the Red Sea and may be driven by gravity gliding on mobile salt layers or by continued Red Sea extension. Envisat InSAR observations of the area show very strong atmospheric signals, which would have made interseismic deformation measurements impossible, if it werent for the availability of MERIS data to correct the InSAR observations. Time-series results of the InSAR data show very low interseismic deformation rates of ~1 mm/year, which are not distinguishable from zero, given the estimated 2 mm/year uncertainty.
The most recent volcanic activity in the region were the 2007-8 Jebel at Tair island (Red Sea) eruption, the 2009 Harrat Lunayyir magmatic intrusion, and the 2011-12 Zubair islands (Red Sea) eruption. We use a combination of Envisat, ERS, ALOS, TerrSAR-X and high-resolution optical imaging to study this activity. The results show that the Harrat Lunayyir intrusion almost made it to the surface to start an eruption, and that its orientation is parallel to the Red Sea, a manifestation of the extensional stress field that governs in the Red Sea region. The dike that fed the Jebel at Tair eruption, on the other hand, is oriented perpendicular to the Red Sea rift axis, and was therefore likely controlled by local stresses within the volcanic edifice, rather than the regional stress field.
The addition to tectonic and volcanic deformation, there is evidence for anthropogenic deformation at many locations within Arabia, primarily due to groundwater and oil exploitation. A dramatic example of over-utilization of groundwater is in Yemen, where 10s of cm/year subsidence is observed in Envisat and ALOS InSAR data.