[J09-1] Geodesy and seismology general contributions I

[J09-1-02] Recent findings on dual tsunami sources: November 1945 Makran (NW Indian Ocean) and December 1908 Messina (Italy) tsunamis

Mohammad Heidarzadeh¹, ^○Kenji Satake², Sebastian Krastel³, David Tappin⁴ (1.Brunel University London, Uxbridge, UK, 2.The University of Tokyo, Tokyo, Japan, 3.University of Kiel, Kiel, Germany, 4.British Geological Survey, Nottingham, UK)

The concept of dual (combined earthquake-landslide) tsunami source has gain weights in tsunami community mostly since the July 1998 Papua New Guinea tsunami where only a dual source was capable of re-producing the coastal runups [Satake & Tanioka, 2003, PAGEOPH; Tappin et al. 2001, Mar. Geol.]. Since then, efforts have been made to re-analyze historical tsunami events in order to address discrepancies between available observations and numerical results based on the state-of-the-art models. Such efforts have helped to find potential locations of co-seismic submarine landslides [e.g., Billi et al., 2008, GRL]. Improved understanding on the mechanism and case studies of dual tsunami sources are vital in accurately mapping the coastal hazards. Here, we discuss two case studies of dual tsunami sources: 1945 Makran (NW Indian Ocean) and1908 Messina (Italy) tsunamis. In a recent study, Heidarzadeh and Satake (2017) [BSSA] showed that the extreme runup of 12-15 m reported in the near-field for the 1945 Makran tsunami was possibly due to a dual source: a 220-km earthquake fault with average slip of ~6 m and a submarine landslide with dimensions of 15 km (length) x 15 km (width) and a thickness of 600 m. Landslide volume was estimated at ~40 km3. The other heavily debated tsunami event is that of December 1908 in Messina whose origin is still debated. Although several earthquake faults have been proposed for this event, none of them has reproduced the observations [e.g. Tinti and Armigliato, 2003, Mar. Geol.]. Landslide sources were proposed for this event based on the limited marine geophysical data with varying success [e.g. Billi et al., 2008, GRL; Favalli et al., 2009, GRL]. New marine geophysical data obtained for the region [Lili et al., 2017, GRL, in revision] helped to more accurately map potential submarine landslide and more accurately model potential tsunamis in this region. We propose a new dual tsunami source for the 1908 Messina tsunami.