1. Application of SASHA for Mt. Etna case Task D: Probabilistic Hazard Assessment Salvatore D'Amico Istituto Nazionale di Geofisica e Vulcanologia Osservatorio Etneo, Catania (Italy)

2. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Regional and local seismicity at Mt. Etna Mt. Etna area is affected by strong regional earthquakes, but also by shallow local earthquakes due to volcano-tectonic faults.

3. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Features of volcano-tectonic earthquakes Moderate magnitude M L ≤ 5.0 High values of epicentral intensity I 0 ≤ X EMS Shallow depth sources H < 2 km b.s.l. Coseismic surface faulting Strong attenuation of the macroseismic intensity ∆I = 4 in 20 km (~70 km in tectonic areas) Macroseismic Catalogue of Mt. Etna from 1832 to 2008 Azzaro et al. (2009) http://www.ct.ingv.it/ufs/macro/ critical parameter

4. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case 1 2 3 X X X Local Regional 50 yrs exposure time 10% probability The process to compute PSHA by SASHA Local seismicity Short exposure times 10, 30 years Local seismicity Short exposure times 10, 30 years The “site approach” performs a Poissonian PSHA using the seismic history at a site, i.e. the dataset of macroseismic intensities available for a given locality

5. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Database and Catalogue 4432 macroseismic observations –Statistical estimation on site 415 localities (Villages, towns, etc.) from 1566 to 2008 Imax IX-X EMS 140 earthquakes from 1000 to 2008 Io EMS (VI - XI-X) M (3.4 - 4.7)

6. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Probabilistic Results of Task B Estimation of probability distributions of the intensity at a site, given the epicentral intensity I 0 and the site-epicenter distance, through a binomial-beta model. I 0 = VIIII 0 = IX (Azzaro et al., 2012) Intensity attenuation at Etna Point sources Isotropic model Linear sources Anisotropic model 15 earthquakes Io > VII IX6.14880.6076 VIII3.92510.5175 VII10.43331.1037 IX1.18440.2501 VIII2.15340.3654 VII3.06290.4248 VI0.98720.239 125 earthquakes Io > VI

7. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case 1915 Linera Earthquake: Io IX-X – M 4.7 Isotropic Vs Anisotropic model Isotropic modelAnisotropic model

8. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case PSHA Map: attenuated data Isotropic model Anisotropic model Exposure time: 30 yr Exposure time: 10 yr Difference: Iso-Ani 10% prob.

9. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case PSHA Map: felt + attenuated data Isotropic model Anisotropic model Exposure time: 30 yr Exposure time: 10 yr 10% prob. Difference: Iso-Ani

10. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Hazard deaggregation: Zafferana (Iexp: VIII) Exposure time 30 yrs - 10% prob. Faults ID YE MO DA LAT LON M Io DIST PROB

11. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Acireale (Iexp VI) Hazard deaggregation Zafferana (Iexp VIII) Nicolosi (Iexp VII) Exposure time 30 yrs - 10% prob.

12. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Variability of hazard at local scale along the volcano edifice High values (XIII - IX) of I EXP Main contribute to hazard by STF and MF Useful tool for establishing a priority of intervention for retrofit actions of urban areas. Identification of earthquakes to be used for scenario in Task F Conclusions Exp. time 30 yrs 10% prob. Exp. time 10 yrs 10% prob. MF STF

13. UPStrat-MAFA 3rd General Meeting 23-26 July 2013, Selfoss, Iceland Task D: Probabilistic Hazard Assessment: Application of SASHA for Mt. Etna case Open questions and Suggestions Dependency of hazard from uncertainties in epicentral intensity Extensive use of the anisotropic model for all earthquakes with known seismogenic fault –Use of a "standard" size for linear source for each Epicentral intensity class Exp. time 30 yrs 10% prob. Exp. time 10 yrs 10% prob.