GNGTS 2015 - Atti del 34° Convegno Nazionale

50 GNGTS 2015 S essione 1.1 Mosca P.; 2006: Neogene basin evolution in the Northern Po Plain (NW Italy). Insights from seismic interpretation, subsidence analysis and low temperature (U-Th)/He thermocronology. �� PhD Thesis. VU University Amsterdam. 190 pp. Sassone P.; 2015: Strutture recenti nord-vergenti a basso angolo in Val Cerrina (Monferrato Casalese): nuove segnalazioni. Abstract Volume 26, pp. 41-42. AIQUA Congress 2015, Torino. Serva L.; 1990: Il ruolo delle scienze della terra nelle analisi di sicurezza di un sito per alcune tipologie di impianti industriali; il terremoto di riferimento per il sito di Viadana (MN) . Bollettino della Società Geologica Italiana, 109(2), 375-411. Stucchi M., Meletti C., Bazzurro P., Camassi R., Crowley H., Pagani M., Pinho R. and Calvi G.M.; 2012: I terremoti del maggio 2012 e la pericolosità sismica dell’area: che cosa è stato sottostimato?, Progettazione Sismica, 3 , 63-73. Turrini C., Angeloni, P., Lacombe, O., Ponton, M., and Roure, F.; 2015: Three-dimensional seismo-tectonics in the Po Valley basin, Northern Italy . Tectonophysics, doi: 10.1016/j.tecto.2015.08.033 Vezzoli, G., Forno, M. G., Andò, S., Hron, K., Cadoppi, P., Rossello, E., & Tranchero, V.; 2010: Tracing the drainage change in the Po basin from provenance of Quaternary sediments (Collina di Torino, Italy). Quaternary international, 222 (1), 64-71. Zerboni, A., Trombino, L., Frigerio, C., Livio, F., Berlusconi, A., Michetti, A. M., and Spötl, C.; 2015: The loess- paleosol sequence at Monte Netto: a record of climate change in the Upper Pleistocene of the central Po Plain, northern Italy. Journal of Soils and Sediments, 15 (6), 1329-1350. Intensity-based source inversions of the M8 earthquakes of Bihar-Nepal (1934) and of Assam (1897); fast KF scenario of the M7.8 Gorkha, 2015 earthquake F. Pettenati, L. Sirovich, D. Sandron Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Trieste, Italy Introduction and seismotectonic context. We apply the KF algorithm (Sirovich, 1996) in the inverse mode (Sirovich and Pettenati, 2004) and in the direct mode (Pettenati et al., 2011) to three earthquakes of the Himalaya-Assam region of the suture between the Indian subcontinent and Eurasia. Nonlinear intensity-based automatic source inversions are performed of the M S 8.1 Shillong, 1897 and of the M S 8.2 Bihar-Nepal, 1934 (Hough and Bilham, 2008) earthquakes and we calculate the fast KF parametric scenario of MMI intensities for the �� moment magnitude M7.8 Gorkha 25 April, at 06.11.26 UTC, 2015 earthquake. The collision between the Indian subcontinent and Eurasia, with crust shortening and underthrusting of the lndian subcontinent beneath the Himalayas and in part beneath the Tibetan Plateau accounts for the tectonic structure of the central area of collision (the Himalayan chain) and of its lateral sectors. In particular, Molnar and Tapponnier (1975) and Tapponnier et al. (1986) comment on the major strike-slip �� faults, bounding Tibet and emanating from it, that seem to accommodate �� rapid eastward extrusion of Tibetan crust out of the way of India’s and southern Tibet’s northward advance. This large-scale phenomenon explains both the composition of the Himalaya (made by slivers of the ancient Indian subcontinent), and the present seismic activity of the chain and of Assam. It will be seen later, however, that underthrusting is still active in southern Assam. Almost one hundred years ago, Argand (1924) understood that the altitude of the Tibetan Plateau should be due to a long underthrusting - perhaps complete - of the Indian subcontinent beneath Tibet, causing a double thickness of the crust and implying very shallow dipping fault zones below the plateau. Nowadays, it is thought that this underthrusting was not complete, but the interpretation by Argand (1924) remains a milestone. Then, in 1975, Molnar and Tapponier (1975) noted that no intermediate or deep earthquakes had been reliably