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The 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazard
Author(s) -
Malagnini Luca,
Herrmann Robert B.,
Munafò Irene,
Buttinelli Mauro,
Anselmi Mario,
Akinci Aybige,
Boschi E.
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl053214
Subject(s) - seismology , geology , seismic hazard , seismic microzonation , sequence (biology) , seismic analysis , environmental seismic intensity scale , earthquake scenario , geotechnical engineering , genetics , biology
Inadequate seismic design codes can be dangerous, particularly when they underestimate the true hazard. In this study we use data from a sequence of moderate‐sized earthquakes in northeast Italy to validate and test a regional wave propagation model which, in turn, is used to understand some weaknesses of the current design spectra. Our velocity model, while regionalized and somewhat ad hoc , is consistent with geophysical observations and the local geology. In the 0.02–0.1 Hz band, this model is validated by using it to calculate moment tensor solutions of 20 earthquakes (5.6 ≥ M W ≥ 3.2) in the 2012 Ferrara, Italy, seismic sequence. The seismic spectra observed for the relatively small main shock significantly exceeded the design spectra to be used in the area for critical structures. Observations and synthetics reveal that the ground motions are dominated by long‐duration surface waves, which, apparently, the design codes do not adequately anticipate. In light of our results, the present seismic hazard assessment in the entire Pianura Padana, including the city of Milan, needs to be re‐evaluated.