Estimation of locations and migration of debris flows on Izu-Oshima Island, Japan, on 16 October 2013 by the distribution of high frequency seismic amplitudes

• We successfully estimated source locations of five large debris flows only from seismic amplitudes.
• In each flow, locations migrated from high altitude to low, probably corresponding to their flow processes.
• Migration velocities and temporal changes of source amplitudes show a large degree of varieties.
• Our results may be utilized for prevention and reduction of various types of disasters.

In the early morning on 16 October 2013, large debris flows resulted in over 30 people dead on Izu-Oshima Island, Japan, which were induced by heavy rainfall from the approaching Typhoon 1326 (Wipha). We successfully estimated the locations and migration processes of five large events of the debris flows, using the spatial distribution of high-frequency seismic amplitudes recorded by a seismic network on the island. The flows occurred on the western flank of the island, almost at the same place as the site where large traces of debris flows were identified after the disaster. During each event of debris flows, the estimated locations migrated downstream with increasing time, from the caldera rim of Miharayama volcano in the center of the island to its western side with a speed of up to 30 m/s. The estimated time series of source amplitudes are different from event to event, exhibiting a large variety of flow sequences while they seem to have repeated at a relatively narrow area over several tens of minutes. The present approach may be utilized for early detection and warning for prevention and reduction of the present type of disasters in the future.