LATE HOLOCENE SEISMO-TURBIDITE INVESTIGATION IN THE SEDIMENTS OF GULF OF AQABA

2021-2-12
Bektaş, Zeynep
The Gulf of Aqaba is located at the southern part of the Dead Sea Fault (DSF), the length of which is reaches approximately to 1200 km, extending up to Amuq valley in southern Turkey. The gulf is characterized by three pull-apart basins accommodating trans-tensional deformation. Although paleo-seismological information on the past devastating earthquakes that occurred on the on-shore part of DSF is available, it is lacking for the off-shore part of the DSF. In order to fill this information gap and to improve our knowledge about the location, 3D geometries and seismic potentials of the active fault segments in the region, the "Interdisciplinary earthquake hazard study - GAST Project" was initiated in the Gulf of Aqaba and Strait of Tiran in 2017. In this context, 23 short cores were collected from the gulf to investigate sedimentary traces of past earthquakes. Among these, 18 cores with lengths ranging between 35 and 107 cm were scanned by ITRAX micro-XRF scanner at a resolution of 0.5 mm. Radiographic imaging was carried out on 4.2 cm-wide and 0.8 cm-thick u-channels, which allows better evaluation of sedimentary structures. The radiographic images reveal that primary sedimentary structures are completely destroyed by extensive bioturbation, hampering the use of vi soft-sediment deformations for detecting past earthquakes. Turbidites, on the other hand, are clearly seen in the radiographs since they were deposited in a very short time and are least affected by bioturbation. In the radiographic images, fining upwards bedding is very common and the uppermost parts of the sequences appear finer and more homogeneous. Turbidites manifested geochemical anomalies in the ITRAX profiles, such as Zr/Ca, Ti/Ca, Rb/Ca confirming the relatively very quick deposition that did not allow almost any significant bio/geochemical contribution from the water column. Magnetic Susceptibility measurements were performed at 0.5 cm intervals along the full length of the cores. Dating of the deposits was performed by radionuclide (210Pb and 137Cs) and radiocarbon (14C) dating. High-resolution inter-core and inter-basinal stratigraphical correlations allowed the identification of turbidites triggered by AD 1068, 1212, 1588, 1839, and 1995 earthquakes. In addition, studies have enabled the source segments of these historical earthquakes to be understood. The segments in the Gulf of Aqaba are thought to have a recurrence interval of about 800 years.
Citation Formats
Z. Bektaş, “LATE HOLOCENE SEISMO-TURBIDITE INVESTIGATION IN THE SEDIMENTS OF GULF OF AQABA,” M.S. - Master of Science, Middle East Technical University, 2021.