Estimation of slip scenarios for megathrust earthquakes: a case study for Peru

Abstract

The recent 2011 Tohoku-oki earthquake occurred in a region where giant megathrust earthquakes were not expected. This earthquake proved the difficulty to assess seismic hazard mainly based on information from historical earthquakes. In this study we propose a methodology to estimate the slip distribution of megathrust earthquakes based on a model of interseismic coupling (ISC) distribution in subduction margins as well as information of historical earthquakes, and apply the method to the Central Andes region in Peru. The slip model obtained from geodetic data represents the large scale features of asperities within the megathrust, which is appropriate for simulation of long period waves and tsunami modelling. For the simulation of a broadband strong ground motion it becomes necessary to introduce small scale complexities to the source slip to be able to simulate high frequency ground motions. To achieve this purpose we propose a “broadband” source model in which large scale features of the model are constructed from our geodetic scenario slip, and the small scale heterogeneities are obtained from a spatially correlated random slip model. The good agreement between the power spectral density (PSD) of our geodetic slip model, and the PSD of a slip model of the 2010 Maule earthquake, suggests that our methodology can be appropriate to typify megathrust earthquakes.