GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.1 107 defined as STEP sensu Govern and Wortel (2005). In this work the grid- search inversion technique was used, constrained on the four hypotheses. Furthermore, constraints have been placed on the five sites mentioned, with a tolerance of ± one degree of intensity. Then we switched the CFTI dataset with intensities outside the damage zone (intensities greater than V) of the shock of 9 January (Fig. 2), avoiding any doubt about the possible influence on the macroseismic estimates of the 11 January event. Results. The results using the complete data set of 11 January are shown in Table 1. The lowest fit is always obtained for the hinterland solution relative to the Scicli- Ragusa-Monte Lauro fault system (SCICLI). In general the results are comparable with the study of Sirovich and Pettenati (2001). Table 2 shows the results obtained using the reduced dataset, considering the influence of the earthquake of 9 January as a foreschock. The SCICLI model is always the best solution and the The STEP hypothesis is better than IBLMAL. But, by this reduced dataset if we don’t put the constrains for the five sites, the best solution became the IBLMAL model. However, in the forward modelling, for IBLMAL we achieve intensity XI for all the five sites, that for the 11 January earthquake don’t justify the best solution. Fig. 2 - Distribution of intensities of CFTI (Boschi et al. , 1995) of the Mw 7.3 earthquake in south-eastern Sicily of 11 January 1693. The gray shaded area is the zone of damage (intensity greater than V) of the earthquake of January 9. The data inside this area were not taken into account in the second phase of inversions. Table 1 - Dataset CFTI full, with constrain of the five sites on the shore (178 site data). Parametres IBLMAL SCOLEN SCICLI STEP Longitude E 15.3 15.09 14.88 15.5 Latitude N 37.3 37.34 37.19 37.25 FPL, s, d, r [°] ** 350, 76, 310 & 242, 58, 300 & 27, 82, 224 & 349, 82, 310 & Depth [km] 7 6 5 14 Length [km] # +36, -40 +36, -40 +29, -32 +34, -30 Mach numb $ +0.56, -0.59 +0.7, -0.58 +0.51, -0.50 +0.52, -0.66 Vs [km/s] 3.61 3.64 3.6 3.82 S mom [N m] 10 20 4.65 4.76 4.67 8.89 FIT 348 150 127 300 ** Fault Plane Solution: strike, dip, rake. & By intensities KF inversion cannot distinguish the polarity. We assume normal faults by tectonic informations. # The length are + in the strike verse; - in antistrike verse. $ The mach number are + in the strike verse; - in antistrike verse.