Frequency-Magnitude relationships for Underwater Landslides of the Mediterranean Sea

Abstract

An updated version of the submarine landslide database of the Mediterranean Sea contains 955 MTDs and 2608 failure scars showing thatsubmarine landslides are ubiquitous features along Mediterranean continental margins. Their distribution reveals that major deltaic wedgesdisplay the larger submarine landslides, while seismically active margins are characterized by relatively small failures. In all regions,landslide size distributions display power law scaling for landslides > 1 km3. We find consistent differences on the exponent of the powerlaw depending on the geodynamic setting. Active margins present steep slopes of the frequency-magnitude relationship whereas passivemargins tend to display gentler slopes. This pattern likely responds to the common view that tectonically active margins have numerousbut small failures, while passive margins have larger but fewer failures. Available age information suggests that failures exceeding 1000km3 are infrequent and may recur every ~40 kyr. Smaller failures that can still cause significant damage might be relatively frequent, withfailures > 1 km3 likely recurring every 40 years. The database highlights that our knowledge of submarine landslide activity with time islimited to a few tens of thousand years. Available data suggest that submarine landslides may preferentially occur during lowstandperiods, but no firm conclusion can be made on this respect, as only 149 landslides (out of 955 included in the database) have relativelyaccurate age determinations. The timing and regional changes in the frequency-magnitude distribution suggest that sedimentation patternsand pore pressure development have had a major role in triggering slope failures and control the sediment flux from mass wasting to thedeep basin