Ground effects induced by the 2012 seismic sequence in Emilia: implications for seismic hazard assessment in the Po Plain (original) (raw)
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The field characterization of Earthquake Environmental Effects occurred in the epicentral area of the 2012 Emilia seismic sequence (mainly liquefaction-type phenomena, ground fractures and hydrological anomalies) has allowed i) to identify in the affected area the zones more susceptible to local geological instability and ii) to make an independent intensity assessment through the ESI 2007 intensity scale. The distribution of ground effects is suggestive of two events of Intensity VIII, even if the maximum intensity might have been even higher (IX?) in San Carlo and Mirabello. Nevertheless, the estimated intensity of the 2012 Emilia earthquake is sensibly less than that recorded in the Po Plain area in historical times (I0 IX to X), and therefore should not be considered the "reference earthquake" for this area.
A Report on the 2012 seismic sequence in Emilia (northern Italy)
Since mid-May 2012, an energetic seismic sequence has affected the northern part of Italy and specifically a wide sector of the Po River Plain. The sequence has been dominated by two main events: a) Mw = 5.9 occurred near Finale Emilia on May 20th at a depth of 6.3 km, and b) Mw=5.8 occurred near Cavezzo on May 29th at a depth of 10.2 km (earthquake location are obtained Istituto Nazionale di Geofisica e Vulcanologia, http://iside.rm.ingv.it/). The effects of the two main shocks can be summarized as follows:
Areal Distribution of Ground Effects Induced by Strong Earthquakes in the Southern Apennines (Italy)
Surveys in Geophysics, 2002
Moderate to strong crustal earthquakes are generally accompanied by a distinctivepattern of coseismic geological phenomena, ranging from surface faulting to groundcracks, landslides, liquefaction/compaction, which leave a permanent mark in thelandscape. Therefore, the repetition of surface faulting earthquakes over a geologictime interval determines a characteristic morphology closely related to seismic potential. To support this statement, the areal distribution and dimensions of effects of recent historical earthquakes in the Southern Apennines are being investigated in detail. This paper presents results concerning the 26 July 1805 earthquake in the Molise region, (I = X MCS, M = 6.8), and the 23 November 1980 earthquake in the Campania and Basilicata regions (I = X MSK, Ms = 6.9). Landslide data are also compared with two other historical earthquakes in the same region with similar macroseismic intensity. The number of significant effects (either ground deformation or hydrological anomalies) versus their minimum distance from the causative fault have been statistically analyzed, finding characteristic relationships. In particular, the decay of the number of landslides with distance from fault follows an exponential law, whereas it shows almost a rectilinear trend for liquefaction and hydrological anomalies. Most effects fall within the macroseismic area, landslides within intensity V to VI, liquefaction effects within VI and hydrologicalanomalies within IV MCS/MSK, hence at much larger distances. A possible correlation between maximum distance of effects and length of the reactivated fault zone is also noted. Maximum distances fit the envelope curves for Intensity and Magnitude based on worldwide data. These results suggest that a careful examination of coseismic geological effects can be important for a proper estimation of earthquake parameters and vulnerability of the natural environment for seismic hazard evaluation purposes.
ABSTRACT November 24, 2004, at midnight (23.59 PM, local time), a moderate earthquake (Ml 5.2, Mw 5.0; focal depth 8 km; source INGV, http://www.ingv.it/terremoti/ bresciano2004/mecc-focale.html) hit the Lake Garda region, within the active fold and thrust belt of the Southern Alps (fig. 1). This earthquake was felt in the whole Northern Italy, from Venice to Milan and Genoa, and abroad, for instance in Switzerland; the epicentral area includes the town of Salò and its surroundings, where significant damage occurred and more than 200 people were left homeless. Epicentral intensity of VII-VIII in the MCS scale has been assigned in a preliminary way based on severe damage at the villages of Clibbio and Pompegnino. Field surveys have been conducted since the day after the earthquake in order to collect all the information on earthquake's ground effects. The analysis of its environ-mental effects is of some interest for two reasons, a) this Rend. Soc. Geol. It., 1 (2005), Nuova Serie, 134-135, 2 ff.
2010
The L'Aquila earthquake occurred on April 6 2009 at 03:32:39 local time. The earthquake (M w =6.3) was located in the central Italy region of Abruzzo. Much of the damage occurred in the capital city of L'Aquila, a city of approximate population 73000, although many small villages in the surrounding region of the middle Aterno river valley were also significantly damaged. In the weeks following the earthquake, the Geo-Engineering Extreme Events Reconnaissance (GEER) international team, comprised of members from different European countries and the U.S., was assembled to provide post-earthquake field reconnaissance. The GEER team focused on the geological, seismological, and geotechnical engineering aspects of the event. We describe the principal seismological findings related to this earthquake including moment tensors of the main shock and two triggered events, the aftershock pattern and its variation with time, tectonic deformations associated with the main shock, surface fault rupture, and the inferred fault rupture plane. We describe damage patterns on a village-to-village scale and on a more local scale within the city of L'Aquila. In many cases the damage patterns imply site effects, as neighbouring villages on rock and soil had significantly different damage intensities (damage more pronounced on softer sediments). The April 6 mainshock was the best-recorded event to date in Italy. We present metadata related to the recording sites and then present preliminary comparisons of the data to GMPEs. Those comparisons support the notion of faster distance attenuation in Italy relative to the average for active regions as reflected in NGA GMPEs. Several incidents of ground failure are then discussed, including a number of rockfalls and minor landslides. Perhaps the most significant incidents of ground failure occurred at Lake Sinizzo, for which we describe a number of slumps and spreads around the lake perimeter. This is documented using field observations as well as LIDAR and bathymetric data.
Engineering Geology, 2018
On December 13 th 1990 a magnitude 5.6 seismic event, felt throughout Sicily, and having maximum seismic intensity VII-VIII, occurred. Although, it is classified as moderate magnitude, it caused causalities and the collapse of a few buildings. Two of the most struck cities were Carlentini and Lentini, located in southeastern Sicily at about 20 km from the instrumental epicenter. In order to evaluate the influence of ground features on the damage distribution, both vulnerability and damage maps were drawn using information collected in about 6000 forms coming from official ascertainments. Significant damage observed in some portions of the investigated areas, appears related to the modest quality of the buildings that were classified as medium to high vulnerability. To evaluate the role played by the geologic setting, two sites were instrumented to measure shearwave velocity of the main lithotypes. Sixty-three ambient vibrations measurements were also performed both in free field and inside some buildings. Moreover, using information coming from geological and geophysical surveys, 1D numerical modelling were done to achieve information about the main ground motion parameters. The results highlight the occurrence of significant site effects and the potential presence of resonance phenomena between site and structure during the occurrence of a seismic event. Seismic site amplifications together with the buildings' vulnerability, observed through damage surveys, contributed to enhance the inherent seismic risk of the investigated area.
Colfiorito 1997 Earthquakes Damages Severity Observationand Site Effects
September 1997 registered the onset of a seismic sequence effecting the Umbria-Marche region (Central Italy), in which earthquakes up to IX MCS degree caused diffused damage over a large area. With respect to villages settled in an intermountain basin near the epicentral area, the resulting damage pattern is investigated to give a better understanding of future local ground motion sensitivity, from a qualitative point of view. Macroseismic survey data are collected and compared with the surface geology of 15 villages and hamlets within a restricted area. It emerges that among these 15 settlements, six individual groups are discernable showing a gradual variation to the damage severity, inside a relatively small area. Such abrupt damage variation is influenced by modest scale lithological transitions. In particular, major effects occurred within the basin in villages settled close to border faults. These observations support models existing in literature, which maintain that edge effects and the generation of diffracted waves in soft basins contribute to a strong shaking at site.