Warning/Evacuation and Monitoring Methods for Earthquake-Induced Landslides

Abstract

Phenomena related to earthquake-induced landslides are diverse and include debris flows, floods, and overflowing due to breaching of landslide dams. They are also characterized by diversity in timing of occurrence, in changes in various phenomena and in the scope or scale of impact. We focus on diverse time-series changes as a characteristic of earthquake-induced landslides. On the basis of these characteristics, the main warning and evacuation measures and monitoring approaches for earthquake-induced landslides are divided into three stages in terms of time elapsed. The warning/evacuation and monitoring methods applicable to each stage are described as below. Stage 1: For several hours starting immediately after the earthquake (short term). People may voluntarily evacuate the area to avoid danger; alternatively, the local mayor may issue an evacuation advisory or order. Because quantitative monitoring with instruments is hard to conduct owing to the unavailability of equipment, warning/evacuation measures at this stage are usually determined by individuals (mayors), depending largely on these individuals’ experiences of sediment disasters. Stage 2: For several hours to several days after the earthquake (medium term). Government assistance and recovery efforts begin with a search for missing persons and efforts to rescue survivors. Monitoring equipment and warning equipment can be installed. On the basis of the results of field investigations and data from equipment, major warning and evacuation measures are put into practice. Monitoring at this stage is directed at (i) warning and evacuation and safety management, and (ii) understanding landslide behavior. Stage 3: For several days to several months after the earthquake (long term). Full recovery efforts are underway. Several days after the earthquake, the evacuation advisory or order may be lifted, depending on the results of observations of landslide behavior and on whether sensors are installed. The purposes of monitoring at this stage are the same as before, namely to understand landslide behavior, secure work safety. Disbanding warning and evacuation systems is added as an additional purpose. We also describe advance preparation for warning/evacuation, and educational activities.

Activities in WG of JLS-ELRP.