Deterministic Seismic Hazard Assessment for the Southern Peru and Northern Chile Segment of the Andean Subduction Zone

Abstract:

The coastal region of southern Peru and northern Chile is located in a mature seismic gap and expecting a great megathrust earthquake, which may release the seismic moment deficit accumulated since 1868 and 1877 respectively. One the most important question is how this seismic gap will break in the future. This question is not only important from a scientific point view but also it is relevant for seismic hazard assessment. In this contribution, we propose a methodology to identify the most suitable region for future earthquakes in a mature seismic gap. We adopt a deterministic approach by using some geophysical/geodetic parameters as b value, trench parallel gravity anomaly and interseismic coupling. These parameters represent a physical constraint for short/long term suitable regions for future great earthquakes. In order to weight the contribution of each parameter, we assume the short-long term seismic index (SLTS index), we perform a Monte Carlo simulation using as a calibration measurement the greatest earthquakes occurred in the region. In order to visualize the regional distribution of the SLTS index in the megathrust, we divide the fault in bins of 20 x 20 km. In each bin, we calculate the SLTS index and the moment deficit since the last greatest earthquake. Model results using this SLTS index highlight the most likely domains of short-long term asperities able to nucleate earthquakes in the region. The slip distribution of the Iquique 2014 earthquake validates the reliability of this SLTS index.