Mapping the extent of seismoturbidites near the southern Dead Sea Fault in the Gulf of Aqaba

Abstract

<p>Despite multiple research efforts since the late 1950’s, many questions regarding the earthquake activity of the Dead Sea Fault (DSF) remain, in particular for its southernmost portion in the Gulf of Aqaba. This is due to its offshore location and little-known interactions with the Red Sea rift system. The emergence of the NEOM city-project in northern Saudi Arabia and the planned King Salman road crossing across the Gulf of Aqaba have made it important to find answers for these questions related to the earthquake hazard of the region. The last major earthquake in the Gulf of Aqaba occurred in 1995 along one of the main strike-slip fault segments in the gulf, bringing both extremities of the fault rupture closer to failure. Studies of the DSF have found that large events along the entire DSF cluster during relatively short active seismic periods lasting about 100-200 years, separated by longer quiescent periods of about 350-400 years. From a tectonic point of view, the time gap between 1995 and the previous major earthquake in AD1588 conforms to this scheme and suggests that the DSF might be ripe for a new earthquake sequence, with the 1995 earthquake as the starter. That said, new results from GPS and InSAR observations have pointed to possible fault creep in the southern part of the gulf, which would significantly decrease the seismic hazard in the area. To explore this possible creep and to test the clustering model, we investigate new sub-bottom profiling data acquired in December 2019 in the Gulf of Aqaba. We aim to map the extent of sand layers present in the different sub-basins of the gulf and to correlate them with seismoturbidite layers found in sediment cores collected in 2018. By looking at the geographic extent of these sand layers, we also aim to define the source of the coarse deposits, or at least, to determine whether they are related to the regular sediment influx or linked to turbidites generated by slope failures during large earthquakes. Our preliminary results indicate that the sub-bottom profiling data allow us to map sand layers up to a depth of about 8 meters. Considering a sedimentation rate in the gulf between 0.2 - 0.4 mm/year, we could be able to gain an overview of the sediment infill of the Gulf of Aqaba over the last 20 ky or more. Even if the resolution of the sub-bottom profiling data is lower than that of the sediment cores, and the assumptions made for the correlation of the sand layers, due to the scattered grid, do not help to constrain properly the source of the deposits, we can still propose a longer-term overview of the earthquake activity and discuss the temporal organization of the large events in the area.</p>