Earthquake-induced Submarine Landslides (EQISLs) and a comparison with their Terrestrial Counterparts: Insights from a New Database

Earthquakes are recognized as the primary cause of submarine landslides. These earthquake-induced submarine landslides can damage seafloor infrastructure (e.g. submarine cables, oil pipes and rigs) and trigger anomalous tsunamis that cannot be explained solely by coseismic deformation. However, due to their underwater occurrence, earthquake-induced submarine landslides are difficult to observe and measure directly, and current understanding of their characteristics and triggering mechanisms remains limited compared to earthquake-induced terrestrial landslides. Historical instances of anomalous tsunamis and submarine cable breaks following earthquakes provide valuable insights into earthquake-induced submarine landslides. This study reviewed 124 global events of anomalous tsunamis and submarine cable breaks following earthquake occurrences since 1900 using the National Oceanic and Atmospheric Administration tsunami database and systematic literature review. The study compiled key parameters of earthquake-induced submarine landslides associated with anomalous tsunamis and submarine cable breaks, such as locations, initial water depths of the headscarp, average seabed slope angles, volumes and landslide types. This study also obtained seismic parameters such as epicentral distances, peak ground acceleration (PGA) and Modified Mercalli Intensity (MMI) from the USGS-ShakeMap to establish a quantitative relationship between earthquake-induced submarine landslides and their seismic triggering parameters. Additionally, a comparison was made between earthquake-induced submarine landslides and earthquake-induced terrestrial landslides with emphasis on differences and similarities in landslide parameters, earthquake magnitudes, seismic parameters PGA and MMI, earthquake magnitude-maximum epicentral distance relationships and triggering mechanisms. It was observed that most of the earthquake-induced submarine landslides occur in shallow nearshore areas and generate tsunamis characterized by high local wave heights. This attribute leaves little or no time for warning and preventive measures. Earthquakes with onshore epicenters or strike-slip mechanisms that trigger submarine landslide tsunamis pose an additional challenge for early warning systems. Compared to earthquake-induced terrestrial landslides, earthquake-induced submarine landslides typically occur on gentler slopes, have larger volumes, are triggered by smaller earthquake magnitudes and exhibit distinct triggering mechanisms. However, they show more similarities than previously anticipated, particularly in terms of seismic parameters (PGA and MMI) and focal mechanisms. The findings of this study contribute to a better understanding of earthquake-induced submarine landslide characteristics and their quantitative relationship with seismic parameters. It highlights the necessity for further research on anomalous tsunamis and submarine cable breaks following earthquakes in order to improve current understanding of triggering mechanisms, frequencies and hazard potential of earthquake-induced submarine landslides. Moreover, given that studies on both earthquake-induced submarine landslides and earthquake-induced terrestrial landslides explore interconnected scientific questions within a unified framework, this study emphasizes the importance of comparing submarine and terrestrial environments in earthquake-induced geological disaster research.