| Popis: |
The 26th June, 1917 tsunamigenic earthquake in Samoa is considered the largest historical event on record to have impacted this region in terms of earthquake magnitude and intensity. Yet, very little is known about the scale and distribution of tsunami impacts for this event compared with the recent 2009 tsunamigenic earthquake which originated in a proximal source region at the Northern Tonga Trench. In this paper, we reconstruct the 1917 tsunami from source to inundation using the BG-Flood numerical modelling suite to understand the magnitude of inundation for this event. Model outputs representing inundation extent and hazard depth intensities at spatially flexible grid resolution (10 m, 20 m and 40 m), are validated using available tide gauge records in Apia harbour and limited observations of runup that were derived from historical records. Results indicate variable modelled-to-observed consistency using available source models, wave and runup validation data. Significant discrepancies in recorded vs modelled wave arrival time at Apia of between 30—40 mins are observed, with modelled runup underestimated in southeast Upolu Island compared with the rest of the country where runup observations are available (e.g., west Savai’i Island). We combine the inundation model with available digital distributions of buildings and roads in the RiskScape multi-hazard risk analysis software, to produce exposure metrics for understanding the likely impacts on present-day coastal asset and population distributions if a similar tsunami were to occur. A comparison between the distribution of hazard risk exposure for the 1917 and 2009 events is discussed along with the uncertainties in our results, with suggestions for future work offered. |
