Publication Date:
2015-01-20
Description:
On May 20 2012 a Ml 5.9 seismic event hit the Emilia Po Plain area (northern Italy) triggering an intense earthquake activity
along a broad area of the Plain. Nine days later, on May 29 a Ml 5.8 event occurred roughly 10 km to the SW of the first main shock; these events
caused 26 victims and several injured and damages. The aftershock area extended for more than 50 km, in WNW-ESE direction, including five
major aftershocks with 5.1≤Ml≤5.3 and more than two thousands of minor events. In general, the seismic sequence was confined in the upper 10
km of depth (ISIDe, http://iside.rm.ingv.it/). The focal mechanisms calculated for the main events and also for several M〉4.5 aftershocks are almost
all consistent with a compression (P-axes) N-S oriented due to thrust fault mechanisms. The two nodal planes, both E-W oriented, show a 40°
southward and 60-70° northward dipping plane (QRCMT, Quick Regional Moment Tensors, http://autorcmt.bo.ingv.it/quicks.html), connected with
the compressional regime of the area. From a tectonic point of view, the active Apennine thrust fronts, buried under the Po Plain Plio-Quaternary
sediments, locally consist of three N-verging arcs. The most external structures, the active Ferrara and Mirandola thrusts and folds are responsible
for the Emilia Romagna 2012 earthquake sequence. Just after the 20th May seismic event, the EMERGEO Working Group was active in surveying
the epicentral area searching for coseismic geological effects. The survey lasted one month, involving about thirty researchers and technicians of
the INGV in field and aerial investigations. Simultaneously, a laboratory-working group gathered, organized and interpreted the observations,
processing them in the EMERGEO Information System (siE), on a GIS environment. The most common coseismic effects are: 1) liquefactions
related to overpressure of aquifers hosted in buried and confined sand layers, occurring both as single cones or through several aligned vents
forming coalescent sand blows; 2) extensional fractures with small vertical throws, apparently organized in an en-echelon pattern, observed mainly
in the eastern sector and in the central area; 3) liquefactions directly associable to fractures where huge amounts of liquefied sand and fine sand
was ejected from fractures tens of meters long. The dip of the fault plane, the depth of the main shock and the magnitude indeed did not induce any
primary rupture at the surface.
Description:
Unpublished
Description:
San Francisco, CA, USA
Description:
2T. Tettonica attiva
Description:
open
Keywords:
Coseismic geologic effects
;
Liquefaction
;
Emilia
;
Italy
;
04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Poster session
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