1,721,016 research outputs found
Electrical resistivity tomography for studying liquefaction induced by the May 2012 Emilia-Romagna earthquake (Mw=6.1, northern Italy)
No full textThis work shows the result of an electrical resistivity tomography (ERT) survey carried out for imaging and characterizing the shallow subsurface affected by the coseismic effects of the Mw=6.1 Emilia-Romagna (northern Italy) earthquake that occurred on 20 May 2012. The most characteristic coseismic effects were ground failure, lateral spreading and liquefaction that occurred extensively along the paleo-Reno River in the urban areas of San Carlo and Mirabello (southwestern portion of Ferrara Province). In total, six electrical resistivity tomographies were performed and calibrated with surface geological surveys, exploratory boreholes and aerial photo interpretations. This was one of first applications of the electrical resistivity tomography method in investigating coseismic liquefaction. © Author(s) 2014. CC Attribution 3.0 License
Magnetotelluric investigation in the High Agri Valley (southern Apennine, Italy)
No full textIn this paper we present the result of a magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy. Several MT soundings were carried out in order to obtain a ∼15 km long 2-D resistivity model with an investigation depth of ∼10 km. The main aim was to provide valuable data on the geological and structural setting of the HAV. The MT model was compared with pre-existing geological, geophysical and seismic data. The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low-medium resistivity layer associated with the Quaternary deposits and to the allochthonous units; and a deeper high resistivity layer related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits. Sharp lateral resistivity variations are interpreted as faults that, on the basis of accurate focal mechanism computations, display normal-faulting kinematics. © Author(s) 2015
Geological and geophysical characterization of the southeastern side of the High Agri Valley (southern Apennines, Italy)
No full textIn the frame of a national project funded by Eni S.p.A. and developed by three institutes of the National Research Council (the Institute of Methodologies for Environmental Analysis, the Institute of Research for Hydrogeological Protection and the Institute for Electromagnetic Sensing of the Environment), a multidisciplinary approach based on the integration of satellite, aero-photogrammetric and in situ geophysical techniques was applied to investigate an area located in the Montemurro territory in the southeastern sector of the High Agri Valley (Basilicata Region, southern Italy). This paper reports the results obtained by the joint analysis of in situ geophysical surveys, aerial photos interpretation, morphotectonic investigation, geological field survey and borehole data. The joint analysis of different data allowed us (1) to show the shallow geological and structural setting, (2) to detect the geometry of the different lithological units and their mechanical and dynamical properties, (3) to image a previously unmapped fault beneath suspected scarps/warps and (4) to characterize the geometry of an active landslide affecting the study area. © Author(s) 2015
Evidence of low-magnitude continued reservoir-induced seismicity associated with the pertusillo artificial lake (Southern Italy)
No full textThe most common observations of reservoir-induced seismicity (RIS) by filling artificial lakes are generally associated with the initial impoundment of the lake or the lake level increase above a previous maximum. Rarely, RIS persists for many years without a decrease in frequency or magnitude; if this occurs, it is called "protracted" or "continued" seismicity. Pertusillo artificial lake in high Agri Valley (southern Italy) is a small reservoir with a water column that fluctuates yearly by about 10-15 m (on average), corresponding to a pressure perturbation at the bottom of the lake of 0.10-0.15 MPa. Although the reservoir was filled in 1963, the microearthquake activity still occurring around the lake allows the categorization of such RIS as continued seismicity. We collected all microearthquakes (ML ≤2.7) recorded near the reservoir by two different seismic networks from January 2005 to June 2012 and analyzed their frequency-magnitude distribution, which showed a b value (b = 1.40) much higher than that expected for the investigated area. Even though the spatial seismicity pattern shows two distinct clusters to the northeast and southwest of the lake, we found that only the southwest seismicity is significantly correlated with the water level. The findings suggest that the physical driving mechanism is the 1D pore fluid pressure diffusion along the northeast-southwest fault zones, connecting the reservoir to the southern termination of the Monti della Maddalena fault system, with an average hydraulic diffusivity of ~7.8 m2/s
Geomorphological fragility and mass movements of the archaeological area of "Torre di Satriano" (Basilicata, Southern Italy)
No full textThis paper describes the results of geomorphological and stability studies carried out in the archaeological site of Satriano di Lucania (Basilicata, Southern Italy), where an important sanctuary was built during the 4th Century B.C. This study is based on a mutidipliscinarity approach including accurate interpretation of aerial photos, geomorphological and geoelectrical surveys , and stability analyses. A description of the stability condition of the archaeological site with reference to the landslide that affects the sacred complex is provided in this work. © 2014 Springer International Publishing
Electrical resistivity imaging for the characterization of the Montaguto landslide (southern Italy)
No full textElectrical Resistivity Tomography surveys were carried out for the characterization of the Montaguto earth-flow, located in the southern Apennines chain (Campania Region, southern Italy). The earth-flow investigated is one of the largest and most complex landslides in Europe with a length of 3.1 × 103 m, a width ranging between 45 and 420 m and an area of about 6.6 × 105 m2. In the spring of 2010, a large reactivation of the earth-flow heavily damaged some strategic infrastructures. In order to mitigate the effects of the mass movement, considerable efforts were carried out by the Italian National Civil Protection Department (DPC) to tackle the emergency. The aim of the study was to contribute to a more accurate geometric reconstruction of the landslide body and to improve the knowledge of the geological setting. Due to the lithological characteristic of the outcropping lithotypes, i.e. Faeto Flysch (calcarenite, clay and marl) and Villamaina Unit (sand and silty clay), the electrical resistivity contrasts were not very pronounced. However, the high-resolution of the electrical tomographies was the key to observe the presence of both lateral and vertical discontinuities that were associated with lithological boundaries, structural features and sliding surfaces. The results of the geoelectrical surveys could be considered for planning additional and more appropriate actions aimed at the stabilization of different portions of the Montaguto landslide. © 2018 Elsevier B.V
Middle to Late Pleistocene activity of the northern Matese fault system (southern Apennines, Italy)
No full textAn integrated investigation including geological, geomorphological, geophysical and structural survey, tephra analyses, 14C and 40Ar/39Ar dating, as well as paleoseismic trenching along the N-Matese fault system is presented. The study allowed the characterization of the tectonic mobility of this structure as well as the associated Bojano basin sedimentary-tectonic evolution since the early Middle Pleistocene, providing also new clues concerning the fault historical activity and the associated Mw > 6.5 earthquakes. We have found lines of evidence for > 1 mm/yr slip rate along the presently buried Bojano fault during the mid Middle Pleistocene, and similar rates for the main fault segments paralleling the Matese flanks. The buried Bojano fault significantly slowed down during the last 300 kyr, ceasing its activity before the Holocene. In turn, the segments outcropping along the Matese flanks reactivated at the onset of Late Pleistocene, after a long period of quiescence (480–110 ka), with robust slip rates that would seem even accelerating in post LGM times. Paleoseismic data suggest the occurrence of four Mw > 6.6 earthquakes in the past 3 ka, three of which match the little known 280 BC event, and the devastating 1456 and 1805 earthquakes. © 2017 Elsevier B.V
Robust identification of periodic behavior in the time dynamics of short seismic series: the case of seismicity induced by Pertusillo Lake, southern Italy
No full textIn this paper, we investigate the time dynamics of the seismicity of the area of the artificial Pertusillo Lake (southern Italy) by using two advanced statistical techniques: the robust periodogram and the singular spectrum analysis. Such methodologies are well suited to unveil the main characteristics (periodicities and long-term trend) of short time series, for which the application of standard statistical techniques fail. Our findings are that the monthly number of earthquakes occurred in the investigated area from 2002 to 2012 reveals the presence of the annual periodicity, which is reasonably linked with the yearly loading/unloading operational cycle of the lake. This indicates that the seismicity of the Pertusillo Lake area is effectively induced by the time-varying water level of the artificial lake. This result from one side sheds light on the nature of the earthquakes occurring in the investigated area as reservoir-induced, but, more generally, from another side suggests a robust manner to investigate the time dynamics of short seismic series. © 2014, Springer-Verlag Berlin Heidelberg
Relationship between seismicity and water level of the Pertusillo reservoir (southern Italy)
No full textThe Pertusillo reservoir, located in the High Agri Valley (southern Italy), represents an example of a site affected by continued reservoir-induced seismicity. Although it has been shown that annual fluctuation can be considered the main forcing of the induced seismicity in this area, an investigation of the relationships between the seismicity and some water level parameters of the Pertusillo reservoir carried out in this paper. The aim is to understand, apart from the annual fluctuation, if one or more of these parameters play a dominant role in inducing seismicity year after year SW of the reservoir. The findings of this study suggest that the exceedance of water levels over the previous maxima did not trigger any historical earthquake. In addition, the daily water level rate and the duration for which the maximum water level is maintained do not play any significant role in inducing seismicity. The maximum amplitude of water level change in a hydrological cycle as low as 8 m appears to be large enough to trigger the seismicity SW of the Pertusillo reservoir, whereas higher maximum amplitudes of water level in a hydrological cycle seem not to increase the seismicity rate. Furthermore, it is shown that a long-lasting increase of the water level may lead to induced earthquakes with larger magnitude. Finally, it is demonstrated that the geology of the area SW of the reservoir may provide favourable conditions for the water level fluctuations to induce seismicity in that region, whereas a different geology to the NE of the reservoir is the cause of negligible pore pressure increase. © 2015-OGS
Integrated near surface geophysics across the active Mount Marzano Fault System (southern Italy): Seismogenic hints
No full textHere, we describe an original geophysical multi-method approach applied to the Mount Marzano Fault System. This is one of the most hazardous seismogenic faults of the Apennines (Irpinia, southern Italy), and it was responsible for the 1980, Mw 6.9, earthquake, along with many others before. We carried out electrical resistivity tomography (ERT), ground penetrating radar (GPR) measurements, and horizontal-to-vertical spectral ratio (HVSR) microtremor analysis along several common transects designed across the potential and/or certain fault traces. The data obtained from these non-invasive, inexpensive, expeditious methods mutually integrate with and complement each other, providing a valuable subsurface image of the near surface fault architecture. ERT depicts the general shallow image of the fault zone and of the fault-controlled sedimentary basin, with the depth of the buried bedrock cross-correlated through ambient-noise HVSR results. GPR delineates the very shallow geometry of the fault and of the associated deformation. Coupled with previous paleoseismological studies, these data allow the evaluation of some fault parameters and the precise locating of the fault trace, to aid future paleoseismological investigations aimed at seismic risk reduction programs. © 2013 Springer-Verlag Berlin Heidelberg
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