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The 2012 Emilia seismic sequence (Northern Italy): Imaging the thrust fault system by accurate aftershock location

Authors
Journal
Tectonophysics
0040-1951
Publisher
Elsevier
Volume
622
Identifiers
DOI: 10.1016/j.tecto.2014.02.013
Keywords
  • Seismology
  • Hypocentral Location
  • Seismic Sequence
  • Velocity Model
  • Thrust Fault System
  • Po Alluvial Plain
Disciplines
  • Earth Science
  • Logic
  • Mathematics

Abstract

Abstract Starting from late May 2012, the Emilia region (Northern Italy) was severely shaken by an intense seismic sequence, originated from a ML 5.9 earthquake on May 20th, at a hypocentral depth of 6.3km, with thrust-type focal mechanism. In the following days, the seismic rate remained high, counting 50 ML≥2.0 earthquakes a day, on average. Seismicity spreads along a 30km east–west elongated area, in the Po river alluvial plain, in the nearby of the cities Ferrara and Modena. Nine days after the first shock, another destructive thrust-type earthquake (ML 5.8) hit the area to the west, causing further damage and fatalities. Aftershocks following this second destructive event extended along the same east-westerly trend for further 20km to the west, thus illuminating an area of about 50km in length, on the whole. After the first shock struck, on May 20th, a dense network of temporary seismic stations, in addition to the permanent ones, was deployed in the meizoseismal area, leading to a sensible improvement of the earthquake monitoring capability there. A combined dataset, including three-component seismic waveforms recorded by both permanent and temporary stations, has been analyzed in order to obtain an appropriate 1-D velocity model for earthquake location in the study area. Here we describe the main seismological characteristics of this seismic sequence and, relying on refined earthquakes location, we make inferences on the geometry of the thrust system responsible for the two strongest shocks.

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