GNGTS 2018 - 37° Convegno Nazionale

288 GNGTS 2018 S essione 2.1 shortly after the tsunami (e.g. http://emergency.copernicus.eu/mapping/list-of-components/ EMSR317/ALL/EMSR317_07PALU) . This presentation provides some preliminary results regarding the numerical simulation of the tsunami. We investigate the complexity of the phenomenon and its unexpected features by taking into account two possible generation mechanisms. The first is obviously the earthquake, for which some detailed finite-fault models are made available over the internet (see for instance https://earthquake.usgs.gov/earthquakes/eventpage/us1000h3p4/finite-fault) . We start from the available fault geometries and heterogeneous slip distributions/rupture mechanisms over the fault to simulate the tsunami initial conditions by means of the Okada (1992) analytical formulae. Secondly, we formulate hypotheses on possible landslides triggered by the seismic shaking by carefully digitizing and analysing some detailed bathymetric maps of the bay, taking also into account some observed collapse phenomena involving coastal structures such as piers. The landslide dynamics is simulated with the aid of the UBO-BLOCK Lagrangian model (e.g. Tinti et al. , 1997; Zaniboni et al. , 2016). For each reconstructed source, the propagation and impact of the ensuing tsunami is modelled by means of the UBO-TSUFD numerical code (Tinti and Tonini, 2013) solving the non-dispersive shallow-water equations. Our results are provided in terms of maximum water elevations over the entire Palu bay and of water elevation time series in selected coastal points. We discuss the capability of each scenario to reproduce the available information on tsunami inundation distances and flow depths in different sectors of the bay, and to match the marigram recorded by the Pantoloan tide gauge. References Muhari A., Imamura F., Arikawa T. and Aftiyanto B.; 2018: Finding of the unexpected tsunami due to strike-slip fault at central Sulawesi, Indonesia on 28 September 2018, from the preliminary field survey at Palu (available at http://itic.ioc-unesco.org/images/stories/itst_tsunami_survey/itst_palu/IRIDeS_report_Palu_survey_20181015. pdf). Okada Y.; 1992: Internal deformation due to shear and tensile faults in a half-space . Bull. Seism. Soc. Am.,  82(2) , 1018-1040. Tinti S., Bortolucci E. and Vannini C.; 1997: A block-based theoretical model suited to gravitational sliding . Nat Hazards, 16 , 1–28. Tinti S. and Tonini R.; 2013: The UBO-TSUFD tsunami inundation model: validation and application to a tsunami case study focused on the city of Catania, Italy . Nat. Hazards Earth Syst. Sci., 13 , 1795–1816. Zaniboni F., Armigliato A. and Tinti S.; 2016: A numerical investigation of the 1783 landslide-induced catastrophic tsunami in Scilla, Italy . Nat Hazards, 84 , S455–S470.