Abstract
We develop an ensemble earthquake rate model that provides spatially variable time-independent (Poisson) long-term annual occurrence rates of seismic events throughout Italy, for magnitude bin of 0.1 units from Mw ≥ 4.5 in spatial cells of 0.1° × 0.1°. We weighed seismic activity rates of smoothed seismicity and fault-based inputs to build our earthquake rupture forecast model, merging it into a single ensemble model. Both inputs adopt a tapered Gutenberg-Richter relation with a single b-value and a single corner magnitude estimated by earthquakes catalog. The spatial smoothed seismicity was obtained using the classical kernel smoothing method with the inclusion of magnitude dependent completeness periods applied to the Historical (CPTI15) and Instrumental seismic catalogs. For each seismogenic source provided by the Database of the Individual Seismogenic Sources (DISS), we computed the annual rate of the events above Mw 4.5, assuming that the seismic moments of the earthquakes generated by each fault are distributed according to the tapered Gutenberg-Richter relation with the same parameters of the smoothed seismicity models. Comparing seismic annual rates of the catalogs with those of the seismogenic sources, we realized that there is a good agreement between these rates in Central Apennines zones, whereas the seismogenic rates are higher than those of the catalogs in the north east and south of Italy. We also tested our model against the strong Italian earthquakes (Mw 5.5+), in order to check if the total number (N-test) and the spatial distribution (S-test) of these events was compatible with our model, obtaining good results, i.e. high p-values in the test. The final model will be a branch of the new Italian seismic hazard map.
Highlights
Probabilistic Seismic Hazard Analysis (PSHA), quantifying the likelihood that ground shaking will exceed certain interesting engineering quantity in a given period of time, provides to society important information on construction standards for risk mitigation
For the declustered catalog with the modified Wiechert method considering Historical Analysis of the Completeness (HAC), an annual seismic rate of 5.68 events with Mw ≥ 4.5, a b-value equal to 0.99 (β = 0.66) and a corner magnitude equal to Mw 7.3: in the Appendix A we show more mathematical details and the estimation of the uncertainty associated with these parameters
We developed a time-independent model that estimates the spatial distribution of the annual seismicity rate (Mw ≥ 4.5) by combining the information contained in a seismic catalog with the information from a seismogenic source database
Summary
Probabilistic Seismic Hazard Analysis (PSHA), quantifying the likelihood that ground shaking will exceed certain interesting engineering quantity in a given period of time, provides to society important information on construction standards for risk mitigation. Hiemer et al [2014] implemented this approach on a European scale for harmonizing seismic hazard, as a result of the large-scale community effort made within the European Union project SHARE [Seismic Hazard hARmonization in Europe, Woessner et al, 2015] They used the European Database of Seismogenic Faults [EDSF; Basili et al, 2013], which includes both crustal faults and subduction zones of the Calabrian, Hellenic and Cyprus arcs. For PSHA in Italy, Valentini et al [2017] built a seismic model integrating the distributed seismicity model with the fault source model To this last work, we developed a model that extends the classical kernel-smoothing method, used for spatial event distribution [Frankel, 1995] with correction for time-varying completeness magnitude [Hiemer et al, 2014]. The model presented in this study was developed with the aim of being applied as a branch of the logic tree to be used for the new Italian seismic hazard map (called the MPS19 project) [Meletti et al, 2019b]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
