Probabilistic Tsunami Hazard Assessment of Quintero Bay, Chile

Quintero bay (~71°32`W; 32°47`S), located at 50 km north of Valparaiso, is an important industrial harbor within the metropolitan area of Central Chile. More than 10 facilities including refineries, power plants and LNG terminals are located in the bay. In recent years, its residents have experienced several episodes of marine pollution due to oils spills and chemical substances, evidencing a high exposure to environmental threats. In addition, the region is also exposed to both earthquakes and tsunamis hazard. Therefore, it becomes very important to develop suitable methodologies to assess the multihazard risk in order to increase community resiliance, since the number of inhabitants increased in 30% in the last 16 years. Even though Quintero bay has an official tsunami inundation map, it only indicates maximum inundation depths based on one single deterministic extreme event. On that ground, the present work implements a probabilistic tsunami hazard assessment (PTHA) which could be combined with other hazards such as marine pollution caused by industrial activities. We develop a synthetic data base of ~400 earthquakes scenarios following the Guttenberg-Richter law and a stochastic slip pattern based on the Karhunen-Loéve (K-L) expansion. The location of the epicenter is defined randomly inside the Central Chile segment, while other parameters (e.g. strike, dip, rake and focal depth) are defined according to available slab models. Tsunami simulations are conducted using the Non-hydrostatic Evolution of Ocean WAVES (NEOWAVE) model with four nested grids; the smallest of which has a grid resolution of 30 m in Quintero bay. Tsunami scenarios are simulated obtaining the arrival time, tsunami amplitude, tsunami runup and inundation depth, thus return periods are defined based on statistical analysis. This approach provides the basis for a multihazard risk analysis which could combine earthquake and tsunami hazards with spills of chemical substances, liquefaction, river flooding, storm surges and/or landslides.