[H-DS12] [EE] Tsunami disaster mitigation

[HDS12-09] Frontal Pop-up Structures and Tsunami Earthquakes

Nugroho Dwi Hananto¹、*Satish Chandra Singh²、Yanfang Qin²、Bertand Beunaiche⁴、Praditya Avianto¹、Frederique Leclerc⁵、Helene Delphine Carton²、Li Linlin³、Paul Tapponnier³ (1.Indonesian Institute of Sciences, Indonesia、2.Institut de Physique du Globe de Paris, France、3.Earth Observatory of Singapore, Nanyang Technological University, Singapore、4.ENSTA Bretagne, France、5.University of Nice Sophia Antipolis, France)

キーワード：tsunami earthquake, surface rupture, pop-up structures

Tsunami earthquakes are special class of rare earthquakes that produce exceptionally large tsunamis from relatively small earthquakes (e.g., Kanamori, 1972; Polet and Kanamori, 2000; Okal, 1988; Lay and Bileck, 2007). These earthquakes are suggested to propagate up to the subduction front with low rupture velocities and stress drops, but it is not possible to produce large tsunamis from a slip on shallow dipping megathrust. Using recently acquired high-resolution seismic reflection, bathymetry and reflectivity data here we report the presence pop-up structures, bounded by steeply dipping thrusts, near the subduction front and fresh traces of seafloor ruptures in the 2010 Mentawai tsunami earthquake rupture zone (Hill et al., 2012; Singh et al., 2011; Lay et al, 2011; Newman et al., 2011; Bilek et al., 2011), indicating that the rupture reached to the seafloor. Using tsunami modelling study, we show that the co-seismic slip on these steeply dipping conjugate thrusts can uplift the water-column, produce a large localised tsunami, and can explain the observed tsunami on the neighbouring islands. These results suggest that the pop-up structures at the subduction front might be the main cause of tsunami during tsunamigenic earthquakes, and can be used for tsunami mitigation study.