Earthquake deficit and seismic hazard along the Levant Fault
Researchers from the Institut de Physique du Globe in Paris, in collaboration with scientists from Jordan's Ministry of Energy and Mineral Resources and Taiwan's National Central University, have estimated the accumulated slip deficit along the Levant Fault using paleoseismological data.
Publication date: 28/04/2018
Press, Research
Related teams :
Tectonics and Mechanics of the Lithosphere
Related themes : Natural Hazards
This deficit, of at least 2m, is high and homogeneous all along the fault, reinforcing the idea that this fault ruptures during short-lived seismic crises separated by longer periods of stress loading, and that we could be approaching such a crisis. The study is published in Nature-Scientific Reports on March 14, 2018.
The Levant fault, also known as the Dead Sea fault, is one of the major faults in the eastern Mediterranean. This fault accommodates the northward displacement of the Arabian plate relative to the Sinai block, at a rate of 5 mm per year. Instrumental seismicity in recent decades has been moderate, with the exception of the Mw 7.3 earthquake in the Gulf of Aqaba in 1995. But the exceptional length of the historical and prehistoric record makes this region particularly well suited to the study of seismic sequences, drawing on the archive and paleoseismological record to determine the return time of major earthquakes along the Levant fault.
In order to constrain the seismic history of this fault, the researchers carried out a paleoseismological trench along the southern section of the fault, in the Wadi Araba, a sparsely populated region where data on historical seismicity remained limited. Combining these new results on the location of historical earthquakes with the vast amount of historical, archaeological and paleoseismological data available in the region, enabled the researchers to construct a comprehensive catalog of seismicity, indicating not only the location of past earthquakes, but also their lateral extension.
The catalog obtained indicates that the fault undergoes seismic crises lasting around 150 to 200 years, during which all the fault segments rupture in cascade, separated by longer quiescent periods of around 400 years. This behavior is known as temporal clustering.
By combining data on the lateral extension of past seismic ruptures for all the earthquakes in their catalog, and scaling laws linking rupture length and mean co-seismic slip, this team was able to calculate the total amount of displacement accommodated along the fault by all the earthquakes documented over the last 1600 years. By comparing the slip accommodated by these earthquakes with the slip accumulated over the same period for a displacement of the fault at a rate of 5mm/year, it was possible to show that at present there is a minimum co-seismic slip deficit of the order of 2m, for the entire stretch of fault between the Gulf of Aqaba in the south and Mount Lebanon in the north. The seismogenic potential of the Levant Fault is therefore laterally homogeneous, and we are entitled to wonder whether the magnitude Mw 7.3 earthquake that occurred in 1995 in the Gulf of Aqaba is not the sign of a new seismic crisis that could rupture the entire fault over the next 1 to 2 centuries.
Réf : Lefevre, M., Klinger, Y., Al-Qaryouti, M., Le Béon, M., & Moumani, K. (2018). Slip deficit and temporal clustering along the Dead Sea fault from paleoseismological investigations. Scientific Reports, 8(1), 4511.
