Research and Teaching Center for Earthquake Geology

Týrnavos, Greece

Research and Teaching Center for Earthquake Geology

Týrnavos, Greece
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Caputo R.,University of Ferrara | Caputo R.,Research and Teaching Center for Earthquake Geology | Sboras S.,National Observatory of Athens | Pavlides S.,Research and Teaching Center for Earthquake Geology | And 3 more authors.
Earth-Science Reviews | Year: 2015

When compiling a database of active and capable faults, or more in general when collecting data for Seismic Hazard Assessment (SHA) purposes, the exploitation of the numerous and different sources of information represents a crucial issue. Also the understanding of their potential and limitations is essential. For example, using only information deriving from historically and/or instrumentally recorded earthquakes, as it has been commonly applied in the past, it is not sufficient and it could be, sometimes, even misleading in terms of SHA. In the present paper, the importance of using geological information for better defining the principal seismotectonic parameters of a seismogenic source is discussed and emphasized. In order to show this, four case studies of active faults recently reactivated by strong earthquakes have been selected from the Greek Database of Seismogenic Sources (GreDaSS). Each seismogenic source is analysed twice and separately for the two sources of information: firstly, on the basis of the single-event effects as mainly provided by historically or instrumentally recorded data, and secondly, on the basis of the cumulative effects consisting of any, mainly geological, evidence caused by multiple and repeated fault reactivations of the specific seismogenic source. The quality and accuracy of the produced results from both sources of information are then discussed in order to define the reliability of the outcomes and especially for calibrating the methodological approaches based on geological data, which have not only an intrinsically different degree of uncertainty and resolution, but also a greater potential in exploitability. As a matter of fact, an improved geological, in its broader sense, knowledge will help to fill in the gap of the geodetically and/or seismologically determined tectonic activity of hazardous regions. Moreover, including in a catalogue also the seismogenic sources that are not associated with historical and/or instrumental earthquakes will have a remarkable impact in future SHA analyses either probabilistic or deterministic ones. © 2015 Elsevier B.V.

Tsodoulos I.M.,University of Ioannina | Stamoulis K.,University of Ioannina | Caputo R.,University of Ferrara | Caputo R.,Research and Teaching Center for Earthquake Geology | And 9 more authors.
Tectonophysics | Year: 2016

The south-dipping Gyrtoni Fault defines the northeastern boundary of the Middle-Late Quaternary Tyrnavos Basin, Central Greece. The recognition and recent tectonic activity of the fault were previously based on mapping, remote sensing analyses and electrical resistivity tomography studies. To understand the Holocene seismotectonic behavior of the Gyrtoni Fault we excavated two paleoseismological trenches. To estimate the timing of past earthquakes using luminescence dating, we obtained twenty five fluvial-colluvial sediment and pottery samples from both the upthrown and the downthrown fault blocks. We applied the Optically Stimulated Luminescence (OSL) dating to coarse grain quartz using the single-aliquot regenerative-dose (SAR) protocol. Our investigations of luminescence characteristics using various tests confirmed the suitability of the material for OSL dating. We found that the estimated OSL ages were internally consistent and agreed well with the available stratigraphical data, archaeological evidence and radiocarbon dates. The performed paleoseismological analysis emphasized the occurrence of three surface faulting events in a time span between 1.42 ± 0.06 ka and 5.59 ± 0.13 ka. Also, we recognized an earlier faulting event (fourth) has been also recognized to be older than 5.59 ± 0.13 ka. The mean throw per event value of 0.50–0.60 m could correspond to a ca. Mw 6.5 earthquake. An average fault slip rate of 0.41 ± 0.01 mm/a and an average recurrence time of 1.39 ± 0.14 ka were also estimated. Our results suggest that the elapsed time from the most recent event (minimum age 1.42 ± 0.06 ka) is comparable with the mean return period. © 2016 Elsevier B.V.

Caputo R.,University of Ferrara | Caputo R.,Research and Teaching Center for Earthquake Geology | Pellegrinelli A.,University of Ferrara | Bignami C.,Italian National Institute of Geophysics and Volcanology | And 4 more authors.
Geomorphology | Year: 2015

In May 2012, two moderate earthquakes (Mw=6.1 and 5.9), associated with a noticeable aftershock sequence affected the eastern sector of the Po Plain, northern Italy. The co-seismic areal uplift events are crucial for a better understanding of the seismotectonics of the broader area and thus for a better assessment of the seismic hazard in the region. In the present study, we compared the results of analyses based on high precision levelling, the DInSAR technique, the distribution of liquefaction occurrences, the geomorphological map of the area and the structural model of the region. The DInSAR technique revealed a marked uplift of the ground (up to 17cm), which was confirmed by high precision levelling. The results of both techniques substantially agreed, although there were some considerable local discrepancies, due to well-documented and diffuse liquefaction phenomena. Some strategic precautions when planning high-precision levelling networks are suggested. © 2015 Elsevier B.V.

Papathanassiou G.,Aristotle University of Thessaloniki | Mantovani A.,University of Ferrara | Tarabusi G.,University of Ferrara | Tarabusi G.,Italian National Institute of Geophysics and Volcanology | And 3 more authors.
Engineering Geology | Year: 2015

On the 20th and 29th of May 2012, two earthquakes occurred in Emilia-Romagna region (Northern Italy) triggering extensive liquefaction of the subsoil units. The consequences of liquefaction have been observed and reported by several agencies in a widespread area. The most impressive liquefaction manifestations were documented in a zone 3-4. km-long and 1. km-wide, where the villages of Sant'Agostino, San Carlo and Mirabello are located. The existing post-earthquake reports and the availability of geotechnical data provided by in-situ tests consist the basic ingredients for a computation of the liquefaction potential parameters within this zone. In particular, the Liquefaction Potential Index (LPI) and Liquefaction Severity Number (LSN) indexes were evaluated and then correlated by considering liquefaction phenomena either observed on site or not. Thus, the existing classifications of the LPI and LSN were evaluated and compared with the observed liquefaction-induced deformations. The latter was applied and validated for the first time within a liquefiable area using post-earthquake data, after the development by Tonkin and Taylor (2013). The outcome of this study shows that a threshold value of LPI around 13 or 14 is better to be taken into account instead of 5 for discriminating sites where liquefaction surface evidences should be expected from the 'non-liquefied' ones. Moreover, from the correlation of the LSN values with the cases of liquefaction-induced ground disruption it is concluded that the proposed threshold value of 10 fits statistically well with our dataset. In addition, a preliminary correlation of LPI and LSN indicates a trend that could be useful in future studies for delineating sites likely to liquefaction. © 2015 Elsevier B.V.

Tarabusi G.,Italian National Institute of Geophysics and Volcanology | Tarabusi G.,University of Ferrara | Caputo R.,University of Ferrara | Caputo R.,Research and Teaching Center for Earthquake Geology
International Journal of Earth Sciences | Year: 2016

The Mirandola anticline represents a buried fault-propagation fold which has been growing during Quaternary due to the seismogenic activity of a blind segment belonging to the broader Ferrara Arc. The last reactivation occurred during the May 2012 Emilia sequence. In correspondence with this structure, the thickness of the marine and continental deposits of the Po Plain foredeep is particularly reduced. In order to better define the shallow geometry of this tectonic structure, and hence its recent activity, we investigated in a depth range which is intermediate between the surficial morphological observations and seismic profiles information. In particular, we carried out numerous passive seismic measurements (single-station microtremor) for obtaining the horizontal-to-vertical spectral ratio. The results of a combined analysis of the peak frequency and its amplitude nicely fit the available geological information, suggesting that this low-cost geophysical technique could be successfully applied in other sectors of wide morphologically flat alluvial plains to investigate blind and completely buried potential seismogenic structures. © 2016 Springer-Verlag Berlin Heidelberg

Fontana D.,University of Modena and Reggio Emilia | Lugli S.,University of Modena and Reggio Emilia | Marchetti Dori S.,University of Modena and Reggio Emilia | Caputo R.,University of Ferrara | And 2 more authors.
Sedimentary Geology | Year: 2015

In May 2012 widespread sand blows formed along buried channels in the eastern sector of the Po Plain (Northern Italy) as a consequence of a series of seismic events with main shocks of Mw 6.1 and 5.9. At San Carlo (Ferrara) a trench dug a few week after the earthquakes exposed sand dikes cutting through an old Reno River channel-levee system that was diverted in the 18th century and was deposited starting from the 14th century (unit A). This sequence overlies a Holocene muddy floodplain deposits and contains scattered sandy channel deposits (unit B) and a Pleistocene channel sand unit (unit C). Sands with inverse and normal grading, concave layering and vertical lamination coexisting along the dikes suggest multiple rhythmic opening and closing of the fractures that were injected and filled by a slurry of sand during the compression pulses, and emptied during the extension phase. The pulse mechanism may have lasted for several minutes and formed well stratified sand volcanoes structures that formed at the top of the fractures. Sands from dikes and from the various units show well defined compositional fields from lithoarenitic to quartz-feldspar-rich compositions. Sands from the old Reno levee and channel fill (unit A) have abundant lithic fragments derived from the erosion of Apennine sedimentary carbonate and terrigenous successions. Composition of the sand filling the dikes show clear affinities with sand layers of the old Reno River channel (Unit A) and clearly differ from any sand from deeper Holocene and Pleistocene layers (Unit B and C), which are richer in quartz and feldspar and poorer in sedimentary lithic fragments. Sorting related to sediment flux variations did not apparently affect the sand composition across the sedimentary structures. Textural and compositional data indicate that the liquefaction processes originated from a relatively shallow source consisting of channel sands located within Unit A at 7.5. m depth. © 2015 Elsevier B.V.

Zuccarello A.R.,University of Catania | Caputo R.,University of Ferrara | Caputo R.,Research and Teaching Center for Earthquake Geology | Gueli A.M.,University of Catania | And 2 more authors.
Bollettino di Geofisica Teorica ed Applicata | Year: 2015

At Piano San Nicola site (Basilicata region, southern Italy) four samples of Glycimeris sp. shells were collected from the uppermost fossiliferous stratigraphic level of one of the main Quaternary marine terraces of the Taranto Gulf, which extends across the external sector of the southern Apennines fold-and-thrust belt, the Bradano Foredeep and the Apulian Foreland. These samples were analysed using the Electron Spin Resonance (ESR) technique, applied for the first time to this area. The obtained new chronological results provided reliable absolute ages ranging between 40.4 ±7.7 ka and 64.0 ±11.2 ka, which are in good agreement with the datings known in literature and obtained by different chronological methods as well as palaeontological inferences. The absolute ages achieved by our study represent fresh evidence supporting the chronological correlation between the marine terrace where Piano San Nicola site is located (Policoro Terrace) and the Marine Isotope Substage (MIS) 3.3. © 2015 - OGS.

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