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Source modelling of the M5-6 Emilia-Romagna, Italy, earthquakes (2012 May 20-29)

  • On 2012 May 20 and 29, two damaging earthquakes with magnitudes M-w 6.1 and 5.9, respectively, struck the Emilia-Romagna region in the sedimentary Po Plain, Northern Italy, causing 26 fatalities, significant damage to historical buildings and substantial impact to the economy of the region. The earthquake sequence included four more aftershocks with M-w, >= 5.0, all at shallow depths (about 7-9 km), with similar WNW-ESE striking reverse mechanism. The timeline of the sequence suggests significant static stress interaction between the largest events. We perform here a detailed source inversion, first adopting a point source approximation and considering pure double couple and full moment tensor source models. We compare different extended source inversion approaches for the two largest events, and find that the rupture occurred in both cases along a subhorizontal plane, dipping towards SSW Directivity is well detected for the May 20 main shock, indicating that the rupture propagated unilaterally towards SE. Based on the focal mechanismOn 2012 May 20 and 29, two damaging earthquakes with magnitudes M-w 6.1 and 5.9, respectively, struck the Emilia-Romagna region in the sedimentary Po Plain, Northern Italy, causing 26 fatalities, significant damage to historical buildings and substantial impact to the economy of the region. The earthquake sequence included four more aftershocks with M-w, >= 5.0, all at shallow depths (about 7-9 km), with similar WNW-ESE striking reverse mechanism. The timeline of the sequence suggests significant static stress interaction between the largest events. We perform here a detailed source inversion, first adopting a point source approximation and considering pure double couple and full moment tensor source models. We compare different extended source inversion approaches for the two largest events, and find that the rupture occurred in both cases along a subhorizontal plane, dipping towards SSW Directivity is well detected for the May 20 main shock, indicating that the rupture propagated unilaterally towards SE. Based on the focal mechanism solution, we further estimate the co-seismic static stress change induced by the May 20 event. By using the rate-and-state model and a Poissonian earthquake occurrence, we infer that the second largest event of May 29 was induced with a probability in the range 0.2-0.4. This suggests that the segment of fault was already prone to rupture. Finally, we estimate peak ground accelerations for the two main events as occurred separately or simultaneously. For the scenario involving hypothetical rupture areas of both main events, we estimate M-w = 6.3 and an increase of ground acceleration by 50 per cent. The approach we propose may help to quantify rapidly which regions are invested by a significant increase of the hazard, bearing the potential for large aftershocks or even a second main shock.show moreshow less

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Metadaten
Author:Simone CescaORCiD, Thomas Braun, Francesco Maccaferri, Luigi Passarelli, Eleonora Rivalta, Torsten DahmORCiDGND
DOI:https://doi.org/10.1093/gji/ggt069
ISSN:0956-540X (print)
Parent Title (English):Geophysical journal international
Publisher:Oxford Univ. Press
Place of publication:Oxford
Document Type:Article
Language:English
Year of first Publication:2013
Year of Completion:2013
Release Date:2017/03/26
Tag:Earthquake dynamics; Earthquake source observations
Volume:193
Issue:3
Pagenumber:15
First Page:1658
Last Page:1672
Funder:BMBF project MINE (Programme GEOTECHNOLOGIEN) [BMBF03G0737]; ERC StG project CCMP-POMPEI
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Erd- und Umweltwissenschaften
Peer Review:Referiert