Magnitude-frequency distribution of submarine landslides in the Gioia Basin (southern Tyrrhenian Sea)

Regional inventories and magnitude-frequency re- lationships provide critical information about landslides and represent a first step in landslide hazard assessment. Despite this, the availability of accurate inventories in the marine en- vironment remains poor because of the commonly low acces- sibility of high-resolution data at regional scales. Evaluating high-resolution bathymetric data spanning the time interval 2007–2011 for the Gioa Basin of the southern Tyrrhenian Sea yielded a landslide inventory of 428 events affecting an area of >85 km2 and mobilizing approximately 1.4 km3 of sediment. This is the first time that this area is studied in such detail, justifying comparison with other areas both onland and offshore. Statistical analyses revealed that the cumulative dis- tribution of the dataset is characterized by two right-skewed probability distributions with a heavy tail. Moreover, evidence of a rollover for smaller landslide volumes is consistent with similar trends reported in other settings worldwide. This may reflect an observational limitation and the site-specific geolog- ic factors that influence landslide occurrence. The robust val- idation of both power-law and log-normal probability distri- butions enables the quantification of a range of probabilities for new extreme events far from the background landslide sizes defined in the area. This is a useful tool at regional scales, especially in geologically active areas where submarine land- slides can occur frequently, such as the Gioia Basin.