Prodelta Slope Stability and Associated Coastal Hazards in Tectonically Active Margins: Gulf of Corinth (Ne Mediterranean)

Abstract

Submarine prodelta instabilities appear as a sequence of rotational block slumps, restricted to the Upper Holocene silty clay deposits (unit A). The individual slump blocks are about 80-150m long and 5-15m in thickness. Slip zones are associated with the deeper Lower Holocene and/or methane gas-charged sediments (unit B). Mud flows appear towards the steeper prodelta slopes. Calculation of slope stability with the Normalised-Soil-Parameter (NSP) method of the normally consolidated prodelta sediments (Lower Holocene unit B), indicates that instabilities could be induced by earthquake ground accelerations from 0.13-0.14 g. Somewhat higher accelerations (0.27-0.30 g) are able to initiate mass failures in overconsolidated prodelta sediments (Upper Holocene unit A). These estimations are in accordance with the observed sediment mass wasting processes. Since the regional expected peak ground acceleration range between 0.10-0.15 g. the prodelta slopes in W. Greece are highly unstable.