NEAR-FIELD TSUNAMI HAZARD MAP PADANG, WEST SUMATRA: UTILIZING HIGH RESOLUTION GEOSPATIAL DATA AND RESEASONABLE SOURCE SCENARIOS

Abstract

Near-field tsunami propagation both in shallow water environments and bore-like wave propagation on land are conducted in this study to obtain fundamental knowledge on the tsunami hazard potential in the city of Padang, Western Sumatra, Republic of Indonesia. As the region proves a huge seismic moment deficit which has progressively accumulated since the last recorded major earthquakes in 1797 and 1833, this investigation focuses on most reasonable seismic sources and possibly triggered nearshore tsunamis in order to develop upgraded disaster mitigations programs in this densely-populated urban agglomeration located on the western shore of Sumatra Island. Observations from continuous Global Positioning Satellite (cGPS) systems and supplementary coral growth studies confirm a much greater probability of occurrence that a major earthquake and subsequent tsunami are likely to strike the region in the near future. Newly surveyed and processed sets of geodata have been collected and used to progress most plausible rupture scenarios to approximate the extent and magnitudes of a further earthquake. Based upon this novel understanding, the present analysis applies two hydronumerical codes to simulate most probable tsunami run-up and subsequent inundations in the city of Padang in very fine resolution. Run-up heights and flow-depths are determined stemming from these most plausible rupture scenarios. Evaluation of outcome and performance of both numerical tools regarding impacts of surge flow and bore-like wave fronts encountering the coast and inundating the city are thoroughly carried out. Results are discussed not only for further scientific purposes, i.e. benchmark tests, but also to disseminate main findings to responsible authorities in Padang with the objective to distribute the most probable dataset of plausible tsunami inundations as well as to address valuable insights and knowledge for effective counter measures, i.e. evacuation routes and shelter building. Following evacuation simulations based on rational assumptions and simplifications reveal a most alerting result as about 260.000 people are living in the highly exposed potential tsunami inundation area in the city of Padang of which more than 90.000 people will need more than 30 min. to evacuate to safe areas.