Marine Deep-Water Free-Fall Cpt Measurements For Landslide Characterisation Off Crete, Greece (Eastern Mediterranean Sea) Part 2: Initial Data From The Western Cretan Sea

Pore pressure and shear strength are major controlling parameters for slope stability, which can be measured in situ using CPT (cone penetration testing) instruments. This paper presents results from initial tests with two free-fall CPT probes deployed in the neotectonically active submarine slope of northern Crete, Greece. Research expedition P336 investigated landslide-prone areas in the Cretan Sea using multibeam swathmapping, seismic reflection profiling, in situ CPT measurements, and gravity coring. Several large landslide complexes at the NE Cretan Margin as well as a small, but steep landslide scarp structure further east were identified on the seismic profiles. CPT devices were deployed in undisturbed slope sediments, across the slide scar, and in the main body of the slide, and remained stuck in the sediment for ~10 minutes to monitor pore pressure dissipation upon insertion. Excess pore pressure after insertion is in a range around 60 kPa in background sediment, and exceeds 80 kPa in the slide deposits. Cone resistance of the slope sediment ranges between 300 and 500 kPa, corresponding to undrained shear strengths of up to 40 kPa. The slid sediments (specifically the headwall material with <10 kPa strength) show velocity-weakening behaviour during ring shear experiments, indicating that those sediments are unlikely to show stable creep and instead may fail catastrophically.