A methodology for tsunami hazard assessment using Green functions

In this study we propose a methodology for fast computation of offshore wave heights of tsunamis generated by a specific initial water disturbance. The method includes the following steps: the source area is discretized into a grid of unity water sources, a linear shallow water (LSW) numerical model is used to pre-compute the corresponding Green functions, the reconstitution of the tsunami waveform is made for a set of possible earthquake sources. We compare these results with the direct LSW computation, to check for the accuracy of the method. We present a case study for the coast of Oman. The Makran subduction zone is used as potential source area, and Green summation is used to produce rapid estimations of water heights at a number of virtual tide gauges located along the shoreline. The results show the effectiveness of the method to save computation time and its use in estimations of tsunami hazard, when there is a need to compute a very large number of potential sources. This work was funded by projects: TAGUS DELTA, CONDRIBER, GEONUM of FCT Portugal, Avaliação do Risco Sísmico e de Tsunami no Concelho de Cascais (IDL-UL); and GTIMS tender no. JRC/IPR/2013/G.2/13/NC.