Tsunami hazard from submarine landslides: scenario-based assessment in the Ulleung Basin, East Sea (Japan Sea)

Abstract

In this study we use a scenario-based approach to highlight potential tsunami hazard from actual Late Pleistocene submarine landslides in the Ulleung Basin: two submarine landslides on the western slope of the Ulleung Basin, north and south of the Hupo Bank (2.53 and 1.12 km3 respectively) and a landslide (15.1 km3) on the continental slope south of the Ulleung Basin. The simulations attempt to highlight the consequences, should one of these events occur at Present. Results of the simulations indicate potential local hazard zones with very local waves < 2 m high in the Korean coast of the East Sea that could result from midsized landslides, not exceeding 3 km3 on the western slope of the basin. Time available for early warning since onset of these events is between 15–30 minutes. On the other hand, the continental margin south of the Ulleung Basin is an area where landslide tsunamis with significant hazard potential could originate. New landslides of similar size to those of the Late Pleistocene could produce tsunami waves > 3 m in the stretch of coastline from Ulsan in the south to Uljin in the north. The timing available for early warning from landslide tsunamis originating in this area is 15–30 minutes along the affected section of the shoreline. We also suggest a Probabilistic Tsunami Hazard Assessment (PTHA) for comprehensive assessments of the Korean coast of the East Sea. PTHA accounts for uncertainties in location, release mechanisms, evolution, and return periods of submarine landslides as well as epistemic uncertainty. However, to constrain these uncertainties detailed information on source areas, recurrence period and dynamics of submarine landslides is necessary and calls for additional data collection and further studies