Source characterization of the 1996 Biak tsunami based on earthquake and landslide scenarios

Abstract

The Biak tsunami event on February 17, 1996, was triggered by a Mw 8.2 earthquake at 5:59 UTC (14:59 local time). Based on the field survey, the maximum tsunami height was not located on the coast that directly faces the earthquake epicenter. The maximum tsunami of up to 7.7 m was recorded at Farusi village on the opposite coast. In addition to the high tsunami hit, the fast arrival time in this village was an anomaly that raised questions regarding the multiple tsunami sources. Previous studies suspected a landslide when a rupture occurred, but no one had yet identified the dimensions and mechanism of the landslide. The purpose of this research is to increase understanding of tsunami generators and answer that question. The COMCOT software is used to perform tsunami simulations, integrating fault and landslide sources simultaneously. This study obtains the Biak tsunami generator from a fault source model with a length of 272 km, a width of 110 km, an average dislocation of 8 m, and a maximum slip of 10.6 m. Also, there are three landslides occurred in the south coast. One of the major landslide source model has dimensions length and width of 5.629 km and 14.595 km, respectively, and a thickness of landslide material of 50 m, with an average slope of the slip plane of 10° located in the Ramardori. These two source models answer the particular questions of the Biak tsunami incident.