Mw6.1 earthquake rocks Northern Italy

An earthquake of magnitude Mw6.1 (EMSC data; USGS: M6.0) rocked Northern Italy on 20 May, 2012 at 2 am UTC. The epicentre was located on 35 km NNW of Bologna in the Po Plain at around 10 km depth. Media report at least 6 people dead and up to 50 injured. Intensities reached up to EMS VIII. Especially old brick buildings suffered severe damages and many collapses are reported.

Moment tensor solutions point to a reverse faulting event. Image source: EMSC (http://www.emsc-csem.org/Earthquake/earthquake.php?id=267440#)

USGS estimated peak ground accelerations in the order of 21% g:

USGS PGA estimations. Image source: USGS (http://earthquake.usgs.gov/earthquakes/shakemap/global/shake/b0009tk0/download/pga.jpg)

The earthquake followed a M4.0 foreshock three hours before, that already caused intensities of V. Large aftershocks are currently occuring, among them several events with M>4.0 and one quake measuring M5.2.

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Generally, the area is characterized by rather moderate seismicity compared to the rest of the country, but strong earthquakes are known from historical sources and paleoseismological investigations.

Studies on Quaternary earthquake activity in the broader area:

• Michetti et al., 2010: Latest Pleistocene to Holocene thrust faulting paleoearthquakes at Monte Netto (Brescia, Italy): lessons learned from the Middle Ages seismic events in the Po Plain. Geophysical Research Abstracts, Vol. 12, EGU2010-12912.
• Michetti et al., 2011: Geological criteria for evaluating seismicity: Lessons learned from the Po Plain, Northern Italy. Grützner, C., Fernández Steeger, T., Papanikolaou, I., Reicherter, K., Silva, P.G., Pérez-López, R., Vött, A. (eds.): Proceedings 2nd INQUA-IGCP567 International Workshop on Active Tectonics, Earthquake Geology, Archaeology and Engineering 19-24 September 2011, Corinth (Greece), ISBN: 978-960-466-093-3, 140-143.
• Chunga et al., 2007: Synsedimentary deformation of Pleistocene glaciolacustrine deposits in the Albese con Cassano Area (Southern Alps, Northern Italy), and possible implications for paleoseismicity. Sedimentary Geology, 196, 1-4, 59-80.
• Burrato et al., 2003: An inventory of river anomalies in the Po Plain, Northern Italy: evidence for active blind thrust faulting. Annals of Geophysics, 46, 5, 865-882.
• Selvaggi et al., 2008: The Mw5.4 Reggio Emilia 1996 earthquake: active compressional tectonics in the Po Plain, Italy. Geophysical Journal International, 144, 1, 1-13
• Weber et al., 2010: GPS-derived motion of the Adriatic microplate from Istria Peninsula and Po Plain sites, and geodynamic implications. Tectonophysics, 483, 214-222.

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