HR: 09:15h
AN: S31C-06    [Abstracts]
TI: A new Kinematic Approach to Calculate Seismic Hazard Scenarios (Intensity and Peak Ground Displacement); an Example in SE Sicily
AU: * Sirovich, L
EM: sirovich@ogs.trieste.it
AF: Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, Sgonico, TS 34010, Italy
AU: Pettenati, F
EM: fpettenati@ogs.trieste.it
AF: Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, Sgonico, TS 34010, Italy
AB: The part of the seismic hazard map of Italy (http:zonesismiche.mi.ingv.it/mappa_ps_apr04/italia.html) that regards SE Sicily has recently been modified on the basis also of the new location of the source of one of the strongest earthquakes that ever struck the Mediterranean basin (in 1693 in SE Sicily; 54,000 casualties; see Sirovich and Pettenati, 2001 in BSSA). That source was located inland according to the KF geophysical inversion of the regional damage patterns of the earthquake of Jan. 11, 1693 and of its destructive foreshock of Jan. 9 (see Gentile et al., 2004 in BSSA, and Sirovich and Pettenati, 2004 in JGR, for the genetic KF inversion technique). The damage patterns of Jan. 9 and 11, 1693 had been evaluated by three different groups of historians and seismologists on three different intensity scales. (Detailed information was available from the reports of the Officers of the "Regno delle Due Sicilie" of the time as well as from many other documents). Previously, both earthquakes were traditionally ascribed to the well known Malta Escarpment, the most prominent physiographical and structural feature of the area, which is found offshore, south-east of Sicily. However, given the inland damage of 1693, an offshore epicenter would imply a mean radius of 45 km for the virtual area of degree XI (70 km for degree X) and, thus, a magnitude of 8.3±0.2 with a fault length of approximately 280 km. This fault source would cross the NE part of Sicily from the southern Jonian Sea to the Island of Lipari in the Tyrrhenian Sea; but tectonically this seems unrealistic. All the inversion tests, however, pointed to a complex source inland which could have hosted both earthquakes. Here, we used our kinematic KF model in the direct mode in a parametric, deterministic-Montecarlo way to produce a seismic hazard scenario, in terms of maximum ground displacement. This scenario will be compared with PSHA results for long recurrence times in the frame of a project of the Civil Protection of Italy and the National Institute for Geophysics and Vulcanology (INGV). New tentative seismic rules based on displacements are the goals of that project (S5, coordinated by E. Faccioli and A. Rovelli). In the present paper, three linear sources were assumed, to accommodate all the area's guessed inland sources, those of 1693 included. The Montecarlo technique was applied to the eleven source parametres of the KF formula, with the purpose of accounting for the large seismotectonic uncertainties we had. In so doing, 33,280 sources were obtained, allowing us to calculate the mean plus-one-standard-deviation scenarios (in seismic intensity and in horizontal displacement). Our mean scenario reaches 40-50 cm (80-90 cm summing one standard deviation), which, as expected, is more than the maximum provisional PSHA values for the 475-year return period (S5 Project, Faccioli 2007); consider that the return period of an earthquake like that in 1693 is unknown, but it could be of the order of thousands of years. The comparison with the damage in 1693 showed that our provisional result is still not cautious enough, however. It is hypothesized that this is due to the asymmetric distribution of the calculated values in each site also because of the presence of the XII intensity upper bound. In Acapulco, we plan to show the parametric scenario obtained using the median values too.
UR: http:zonesismiche.mi.ingv.it/mappa_ps_apr04/italia.html
DE: 7203 Body waves
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Seismology [S]
MN: 2007 Joint Assembly