Triggering factors and tsunamigenic potential of a large submarine mass failure on the western Nile margin (Rosetta Area, Egypt)

Abstract

A large-scale mass-transport deposit (MTD) called Sl6 was recognized on the upper slope of the western Nile margin, downslope from of a 30 km-long scarp located along the outer shelf. Regional mapping indicated that this MTD extends on nearly 505 km2 and involved about 14 km3 of Pleistocene-Holocene sediment. Sl6 was triggered between 10 and 9 kyr BP, during the Holocene sea-level rise and coeval pluvial period (increased river flow). The consequent enhanced sediment supply on the upper slope and the outer shelf area caused local overburdening. This factor combined with the potential accumulation of gas in the sediment and earthquake activity is thought to have been the main factor triggering the Sl6 MTD. From the estimated volume of the MTD, a potential slide-generated tsunami was numerically simulated using the GEOWAVE software. The results indicate that the ∼80 km wide Egyptian continental shelf protects the main part of the coastline from a slide-induced tsunami coming from the Rosetta area. An exception is the part of the coastline around Alexandria because focussing and shoaling processes can be simulated very close to the coast.