Liquefaction phenomena associated with the Emilia earthquake sequence of May–June 2012 (Northern Italy)

In this paper we present the geological effects induced by the 2012 Emilia seismic sequence in the Po Plain. Extensive liquefaction phenomena were observed over an area of ~ 1200 km<sup>2</sup> following the 20 May, <i>M</i><sub>L</sub> 5.9 and 29 May, <i>M&...

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Main Author: Emergeo Working Group
Format: Article
Language:English
Published: Copernicus Publications 2013-04-01
Series:Natural Hazards and Earth System Sciences
Online Access:http://www.nat-hazards-earth-syst-sci.net/13/935/2013/nhess-13-935-2013.pdf
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spelling doaj-3084f85fc2d34a3f870f0e4e48a977382020-11-25T00:42:36ZengCopernicus PublicationsNatural Hazards and Earth System Sciences1561-86331684-99812013-04-0113493594710.5194/nhess-13-935-2013Liquefaction phenomena associated with the Emilia earthquake sequence of May&ndash;June 2012 (Northern Italy)Emergeo Working GroupIn this paper we present the geological effects induced by the 2012 Emilia seismic sequence in the Po Plain. Extensive liquefaction phenomena were observed over an area of ~ 1200 km<sup>2</sup> following the 20 May, <i>M</i><sub>L</sub> 5.9 and 29 May, <i>M</i><sub>L</sub> 5.8 mainshocks; both occurred on about E–W trending, S dipping blind thrust faults. We collected the coseismic geological evidence through field and aerial surveys, reports from local people and Web-based survey. On the basis of their morphologic and structural characteristics, we grouped the 1362 effects surveyed into three main categories: liquefaction (485), fractures with liquefaction (768), and fractures (109). We show that the quite uneven distribution of liquefaction effects, which appear concentrated and aligned, is mostly controlled by the presence of paleo-riverbeds, out-flow channels and fans of the main rivers crossing the area; these terrains are characterised by the pervasive presence of sandy layers in the uppermost 5 m, a local feature that, along with the presence of a high water table, greatly favours liquefaction. We also find that the maximum distance of observed liquefaction from the earthquake epicentre is ~ 30 km, in agreement with the regional empirical relations available for the Italian Peninsula. Finally, we observe that the contour of the liquefaction observations has an elongated shape almost coinciding with the aftershock area, the InSAR deformation area, and the I ≥ 6 EMS area. This observation confirms the control of the earthquake source on the liquefaction distribution, and provides useful hints in the characterisation of the seismogenic source responsible for historical and pre-historical liquefactions.http://www.nat-hazards-earth-syst-sci.net/13/935/2013/nhess-13-935-2013.pdf
collection DOAJ
language English
format Article
sources DOAJ
author Emergeo Working Group
spellingShingle Emergeo Working Group
Liquefaction phenomena associated with the Emilia earthquake sequence of May&ndash;June 2012 (Northern Italy)
Natural Hazards and Earth System Sciences
author_facet Emergeo Working Group
author_sort Emergeo Working Group
title Liquefaction phenomena associated with the Emilia earthquake sequence of May&ndash;June 2012 (Northern Italy)
title_short Liquefaction phenomena associated with the Emilia earthquake sequence of May&ndash;June 2012 (Northern Italy)
title_full Liquefaction phenomena associated with the Emilia earthquake sequence of May&ndash;June 2012 (Northern Italy)
title_fullStr Liquefaction phenomena associated with the Emilia earthquake sequence of May&ndash;June 2012 (Northern Italy)
title_full_unstemmed Liquefaction phenomena associated with the Emilia earthquake sequence of May&ndash;June 2012 (Northern Italy)
title_sort liquefaction phenomena associated with the emilia earthquake sequence of may&ndash;june 2012 (northern italy)
publisher Copernicus Publications
series Natural Hazards and Earth System Sciences
issn 1561-8633
1684-9981
publishDate 2013-04-01
description In this paper we present the geological effects induced by the 2012 Emilia seismic sequence in the Po Plain. Extensive liquefaction phenomena were observed over an area of ~ 1200 km<sup>2</sup> following the 20 May, <i>M</i><sub>L</sub> 5.9 and 29 May, <i>M</i><sub>L</sub> 5.8 mainshocks; both occurred on about E–W trending, S dipping blind thrust faults. We collected the coseismic geological evidence through field and aerial surveys, reports from local people and Web-based survey. On the basis of their morphologic and structural characteristics, we grouped the 1362 effects surveyed into three main categories: liquefaction (485), fractures with liquefaction (768), and fractures (109). We show that the quite uneven distribution of liquefaction effects, which appear concentrated and aligned, is mostly controlled by the presence of paleo-riverbeds, out-flow channels and fans of the main rivers crossing the area; these terrains are characterised by the pervasive presence of sandy layers in the uppermost 5 m, a local feature that, along with the presence of a high water table, greatly favours liquefaction. We also find that the maximum distance of observed liquefaction from the earthquake epicentre is ~ 30 km, in agreement with the regional empirical relations available for the Italian Peninsula. Finally, we observe that the contour of the liquefaction observations has an elongated shape almost coinciding with the aftershock area, the InSAR deformation area, and the I ≥ 6 EMS area. This observation confirms the control of the earthquake source on the liquefaction distribution, and provides useful hints in the characterisation of the seismogenic source responsible for historical and pre-historical liquefactions.
url http://www.nat-hazards-earth-syst-sci.net/13/935/2013/nhess-13-935-2013.pdf
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