הגיאולוגיה של גלישות המדרון התת-ימיות מול חופי ישראל והסכנה הגיאולוגית הנובעת מהן

Bathymetric grids with 15 – 50 m/pixel resolution were used to map over four hundred submarine landslides and numerous fault scarps exposed on the continental slope off the southeastern Mediterranean Israeli coast. Landslide scars are found at water depth ranging between 130 m to 1000 m, in sites where slopes exceed a critical gradient of about 4° - 5°. Landslide surface areas range from 0.0024 km2 to 91 km2, where the most probable slide area is 1.6x10-2 km2. In general landslides in the north of the studied area are smaller and occur at shallower depth than the southern ones. Landslides show a hierarchical pattern, resulting from sequential, retrograding, slope-failure events and are also observed to interact with a group of faults oriented sub-parallel to the coast. These faults are a result of salt tectonic related extension, their scarps forming elongated step-like morphological features rupturing the surface of the continental slope, as well as the deeper sea floor.

The morphology of the landslides suggests that these landslides are recent, apparently younger than 50,000 years. As a validation of this age, landslide events are dated using radiocarbon, by analyzing selected marine-cores sampled from landslide scars. Results are consistent with the above age. The triggering mechanism is not clear yet, though several conditions which are known to promote slope instability prevail in the studied area: submarine slope gradients are close to the inferred critical slope angle; continuous sedimentation increases the load on the slope; active salt tectonic results in an overall extension and surface rupturing by normal faults; the studied area is merely 100 kilometers away from seismogenic plate boundaries; medium earthquakes capable of triggering slope instability occur in the studied area; and finally, apparent existence of gas close to the surface. Hence, it is suggested that submarine slope failure events in the studied area are also possible in the future. Thus, submarine slope failure must be considered as part of geo-hazard evaluation to offshore facilities along the Israeli coast.


תאריך 22/04/2018 - 23/04/2018
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