http://hdl.handle.net/2122/202 2013-05-25T00:37:02Z http://hdl.handle.net/2122/8401 Title: Automatic detection of landslides at Stromboli using neural network analysis of seismic signals Authors: D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Esposito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Peluso, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; De Cesare, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Orazi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Scarpato, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: Landslides along the Sciara del Fuoco flank of Stromboli volcano are generally accompanied by c1istinctive seismic signals which can be used for srudying this phenomenon. These signals are characterìzed by a spectral content with higher frequencies and a wider band than the typical explosion quakes and volcanic tremor signals which are continuously recorded at Stromboli. Furthermore their amplirude envelope usually shows a cigar-like shape. These two fearures make the detection of such signals quite easy. The detection of landslides at Stromboli has shown to be an important shortterm precursor of effusive eruptions. Before the Feb. 27th 2007 eruption, the opening of the effusive vents was preceded by few hours oI increased occurrence of landslide signals (Martini et al., 2007). Furthermore since the Sciara del Fuoco has shown significant instabilities during the 2002-2003 eruption, the automatic detection of landslide signals is an important monitoring tool for notifying variations in the stability of this flank. We propose a technique based on a Multi Layer Perceptron (MLP) neural network which has shown excellent performances. The network is composed of two layer of neurons, the hidden and the output. The hidden layer is composed of 4 neurons while the output layer is composed by a single neuron whose output value ranges between Oand 1, with values higher than a given threshold (e.g. 0.5) meaning positive detection. The continuous seismic signals are analysed using moving windows of 24 s, with an overlap of 12 s. For each of these windows the neural output is computed. The waveforms of each time window are parametrized using both their spectrogram and their amplirude envelope. The spectrogram is described using the Linear Preclictive Cocling (L'PC) technique which allows to represent the spectral content using a limited number of coefficients. The whole signal is c1ivided into 8 sub-windows of 5.12 s length, with an overlapping of 2.56 s. For each sub-window we compute 6 LPC coefficients, so each spectrogram is described by only 48 coefficients. The amplirude envelope is defined by computing the c1ifference between the maximum and minimum value over 1 s sub-windows obtaining 24 coefficients. In conclusion we use an input vector composed of 72 elements (48+24). This vector has shown to be an efficient and compact representation of the raw signal (composed of 1200 samples) (Esposito et al. 2006). The dataset used for determining the network parameters is composed of 537 signals, c1ivided in two classes: 267 landslide signals and 270 other signals (explosions and tremor). The classification of these signals has been performed by analysts. The training is carried out using subsets of 5/8 of the total dataset. The testing subsets are composed by the remaining 3/8. The network has shown a performance of about 98.7%. This value is an average over 6 random permutations of the dataset. A preliminary real-rime automatic system has already been implemented. This system performs continuous analysis of the seismic signals, publishing them on internal web pages. It allows a detection of the landslides and a comparison with the past activity on arbitrary rime intervals. 2009-05-31T22:00:00Z http://hdl.handle.net/2122/8391 Title: Calving
 event 
detection 
by
 observation 
of 
seiche 
effects 
on 
the
 Greenland 
fjords Authors: Walter, F.; Swiss
 Seismological 
Service, 
ETH 
Zürich,
 Switzerland; Laboratory
 of
 Hydraulics,
 Hydrology 
and
 Glaciology,
 ETH
 Zürich,
 Switzerland; Olivieri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Clinton, J.; Swiss
 Seismological 
Service, 
ETH 
Zürich,
 Switzerland Abstract: With mass loss from the Greenland ice sheet accelerating and spreading to higher latitudes, the quantification of mass discharge in the form of icebergs has recently received much scientific attention. Here, we make use of very low frequency (0.001-0.01 Hz) seismic data from three permanent broadband stations installed in the summers of 2009/2010 in northwest Greenland in order to monitor local calving activity. At these frequencies, calving seismograms are dominated by a tilt signal produced by local ground flexure in response to fjord seiching generated by major iceberg calving events. A simple triggering algorithm is proposed to detect calving events from large calving fronts with potentially no user interaction. Our calving catalogue identifies spatial and temporal differences in calving activity between Jakobshavn Isbræ and glaciers in the Uummannaq district some 200 km further north. The Uummannaq glaciers show clear seasonal fluctuations in seiche-based calving detections as well as seiche amplitudes. In contrast, the detections at Jakobshavn Isbræ show little seasonal variation, which may be evidence for an ongoing transition into winter calving activity. The results offer further evidence that seismometers can provide efficient and inexpensive monitoring of calving fronts. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8353 Title: Automated control procedures and first results from the temporary seismic monitoring of the 2012 Emilia sequence Authors: Marzorati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Carannante, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Cattaneo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; D'Alema, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Frapiccini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Ladina, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Monachesi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Spallarossa, D.; Dipteris, Università di Genova Abstract: After moderate to strong earthquakes in Italy or in the surrounding areas, the Istituto Nazionale di Geofisica e Vulcanologia (INGV; National Institute for Geophysics and Volcanology) activates a temporary seismic network infrastructure. This is devoted to integration with the Italian National Seismic Network (RSN) [Delladio 2011] in the epicentral area, thus improving the localization of the aftershocks distribution after a mainshock. This infrastructure is composed of a stand-alone, locally recording part (Re.Mo.) [Moretti et al. 2010] and a real-time telemetered part (Re.Mo.Tel.) [Abruzzese et al. 2011a, 2011b] that can stream data to the acquisition centers in Rome and Grottaminarda. After the May 20, 2012, Ml 5.9 earthquake in the Emilia region (northern Italy), the temporary network was deployed in the epicentral area; in particular, 10 telemetered and 12 stand-alone stations were installed [Moretti et al. 2012, this volume]. Using the dedicated connection between the acquisition center in Rome and the Ancona acquisition sub-center [Cattaneo et al. 2011], the signals of the real-time telemetered stations were acquired also in this sub-center. These were used for preliminary quality control, by adopting the standard procedures in use here (see next paragraph, and Monachesi et al. [2011]). The main purpose of the present study is a first report on this quality check, which should be taken into account for the correct use of these data 2012-09-30T22:00:00Z http://hdl.handle.net/2122/8305 Title: Minimum 1-D velocity model in Southeastern Sicily (Italy) from local earthquake data: an improvement in location accuracy Authors: Musumeci, C.; Dipartimento di Scienze Geologiche, Università di Catania, Catania, Italy; Di Grazia, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Gresta, S.; Dipartimento di Scienze Geologiche, Università di Catania, Catania, Italy Abstract: The monitoring of seismic activity in Southeastern Sicily (Italy) has been recently improved by a digital seismic network. This effort has produced a homogeneous and complete dataset which we used to define a reference 1-D velocity model. We have inverted P- and S-wave arrival times from 51 selected local earthquakes by using several initial velocity and layer thickness models. Then, the range of possible velocity models obtained was tested with earthquake locations to select the best velocity model. Improvements in location accuracy by using the Minimum 1-D velocity model, with respect to the locations obtained by using the routine velocity model, were evidenced from the reduced residuals, the smaller estimated location errors, and the increased tendency of foci to cluster. The distribution of relocated hypocenters confirmed the lack of seismic activity in the central part of the area. 2003-02-24T23:00:00Z http://hdl.handle.net/2122/8165 Title: Focal parameters, depth estimation, and plane selection of the worldwide shallow seismicity with M s ! 7.0 for the period – 1900– 1976 Authors: Selva, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia Abstract: A worldwide seismic catalog of source parameters is an important tool in many geophysical studies. Such a kind of database is available only since 1977 with the CMT catalog. The main goal of this paper is to compile a similar catalog for the time period 1900–1976 estimating the focal parameters of shallow seismicity (depth 70 km) with Ms ! 7.0 (607 events). In particular, this new catalog (FM0076) contains strike, dip, rake, and depth estimations for 588 earthquakes in the period 1900–1976. At each estimate two reliability flags are assigned. The first is linked to the availability of data, and the second is given by comparing focal mechanism estimations and the tectonics of the epicentral area. The estimation procedure is based on the knowledge of the moment tensor of shallow earthquakes after 1977. From these data, the new concept of Weighted Cumulative Moment Tensor (WCMT), which represents such a kind of moment tensor for a mean earthquake in the epicentral area, leads to estimate the focal parameters. The estimation method is also tested by comparing out our data set for the period 1977–1989 with the CMT one (91 events). This comparison reveals a good agreement between the two methods and confirms the reliability of the catalog FM0076. 2004-05-14T22:00:00Z http://hdl.handle.net/2122/8039 Title: Magnetic and seismic reflection study of Lake Cheko, a possible impact crater for the 1908 Tunguska Event Authors: Gasperini, L.; CNR-Ismar Bologna; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Stanghellini, C.; INAF-Bologna; Stanghellini, G.; CNR-Ismar Bologna; Del Bianco, F.; CNR-Ismar Bologna; Serrazanetti, M.; CNR-Ismar Bologna; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: A major explosion occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2,000 square km of taiga; pressure and seismic waves detected as far as 1,000 km away; bright luminescence in the night skies of Northern Europe and Central Asia; and other unusual phenomena. This “Tunguska Event” is probably related to the impact with the Earth of a cosmic body that exploded about 5-10 km above ground, releasing in the atmosphere 10-15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report here results from a magnetic and seismic-reflection study of a small (~500 m diameter) lake, Lake Cheko, located about 8 km NW of the inferred explosion epicenter, that was proposed to be an impact crater left by a fragment of the Tunguska Cosmic Body. Seismic-reflection and magnetic data revealed a P-wave velocity/magnetic anomaly close to the lake center, about 10 m below the lake floor; this anomaly is compatible with the presence of a buried stony object and supports the impact crater origin for Lake Cheko. 2012-05-11T22:00:00Z http://hdl.handle.net/2122/8027 Title: Sequential integrated inversion of tomographic images and gravity data: an application to the Friuli area (Northeastern Italy) Authors: Bressan, G.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Cussignacco (UD), Italy; Gentile, G. F.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Cussignacco (UD), Italy; Tondi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; de Franco, R.; Consiglio Nazionale delle Ricerche, Ist. Dinamica dei Processi Ambientali, Milano, Italy; Urban, S.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Cussignacco (UD), Italy Abstract: The three-dimensional pattern of elastic moduli (bulk modulus, Young modulus, shear modulus) of the upper crust (0-10 km depth) has been determined in the Friuli area (north-eastern Italy) from the 3D Vp, Vp/Vs and density structures. Firstly, 3D Pwave velocity and P to S velocity ratio were modeled by joint inversion for hypocentres and velocity structure. Then, we apply the tomographic inversion method of Sequential Integrated Inversion (SII) to recover the three dimensional density structure. The pattern of the elastic moduli is characterized by marked lateral and depth variations that reflect the geologic-structural heterogeneity of the area, produced by the superposition of several tectonic phases with different orientations of the principal axes of stress. The bulk (K), Young (E) and shear (G) moduli image a high rigidity body with an irregular shape, at 4-8 km depth. The body is characterized by G ≥ 3.2·1010 N·m-2, K ≥ 6.8·1010 N·m-2 and E ≥ 8.4·1010 N·m-2 and is associated to platform limestones and dolomitic rocks. The seismicity is mainly located along the sharp variations of the moduli pattern, in or adjacent to high rigidity zones. The most severe earthquakes (ML between 4.5 and 6.4), occurred in the study area from 1976 to the present day, are located in a transition zone from high to low rigidity patterns. Our interpretation is that the elastic moduli variations, closely related to variability in rock mechanical properties, influence the occurrence of earthquakes by processes of stress concentrations. The values of the elastic moduli recently obtained from laboratory measurements on the main lithologic units fall in the middlehigh range of the values obtained with the present investigation. Keywords: Seismic tomography, gravity anomalies, seismicity, elastic moduli, Friuli, NE Italy 2012-05-31T22:00:00Z http://hdl.handle.net/2122/7979 Title: Reference seismic velocity Earth model for Italy from local source tomography and 30 years of controlled source seismology data Authors: Di Stefano, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Kissling, E.; Institute of Geophysics, ETH, Zurich, Switzerland; Chiarabba, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Baccheschi, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: We present here a new high resolution regional P-wave velocity model for the lithosphere beneath the Italian region obtained by including information on the Moho topography, and integrating results from local earthquake tomography with 30 years of CSS data, applying the method of Waldhauser (1996). For the 3D moho map, we extended the crustal model, already available for the Alps by Lippitsch et al., 2003, to the Italian peninsula, Corsica, Sardinia, and Sicily. The tomographic model is obtained by inverting 166,000 Pg and Pn arrival times large part of which have been automatically picked and consistently weighted with an advanced automatic picking system (Aldersons, 2004). The resolution of the obtained velocity model is consistently higher and the grid spacing consistently smaller than in previous tomographic works targeting the same region. We are able to image the complex geometry of this part of the subduction-collision system between the Eurasian and African plates adding important details to the overview derived by the teleseismic tomography. Our results clearly show the plate boundary at Moho level from the Alps to the Southern Apennines and the Calabrian Arc in a volume unresolved in previous studies. The use of global 1D velocity models based on the flat Earth assumption is a pre-requisite to refine and interpret images and seismic responses of the earth obtained with geophysical studies (P and S tomography, surface wave tomography etc). Our model is suitable as a good starting point for a 3D velocity reference model of the crust and upper mantle beneath the Mediterranean area to be extended to the Adriatic Sea and to the Ionian Sea, with benefit for earthquakes location,teleseismic tomography, focal mechanisms and CMT 2005-04-23T22:00:00Z http://hdl.handle.net/2122/7971 Title: IMAGING THE ACTIVE STRESS FIELD OF THREE SEISMOGENIC AREAS ALONG THE APENNINES AS REVEALED BY CRUSTAL ANISOTROPY Authors: Pastori, Marina; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Margheriti, Lucia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Piccinini, Davide; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; De Gori, Pasquale; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Di Bucci, Daniela; Dipartimento della Protezione Civile; Barchi, Massimiliano R.; Università degli studi di Perugia Editors: seno, silvio; Università di Pavia Abstract: During the last decades, the study of seismic anisotropy has provided useful information for the interpretation and evaluation of the stress field and active crustal deformation. Seismic anisotropy can yield valuable information on upper crustal structure, fracture field, and presence of fluid-saturated rocks crossed by shear waves. Several studies worldwide demonstrate that seismic anisotropy is related to stress-aligned, filled-fluid micro-cracks (EDA model). An automatic analysis code, “Anisomat+”, was developed, tested and improved to calculate the anisotropic parameters: fast polarization direction (φ) and delay time (∂t). Anisomat+ has been compared to other two automatic analysis codes (SPY and SHEBA) and tested on three zones of the Apennines (Val d’Agri, Tiber Valley and L’Aquila surroundings). The anisotropic parameters, resulting from the automatic computation, have been interpreted to determine the fracture field geometries; for each area, we defined the dominant fast direction and the intensity of the anisotropy, interpreting these results in the light of the geological and structural setting and of two anisotropic interpretative models, proposed in the literature. In the first one, proposed by Zinke and Zoback, the local stress field and cracks are aligned by tectonics phases and are not necessarily related to the presently active stress field. Therefore the anisotropic parameters variations are only space-dependent. In the second, EDA model, and its development in the APE model fluid-filled micro-cracks are aligned or ‘opened’ by the active stress field and the variation of the stress field might be related to the evolution of the pore pressure in time; therefore in this case the variation of the anisotropic parameters are both space- and time- dependent. We recognized that the average of fast directions, in the three selected areas, are oriented NW-SE, in agreement with the orientation of the active stress field, as suggested by the EDA model, but also, by the proposed by Zinke and Zoback model; in fact, NW-SE direction corresponds also to the strike of the main fault structures in the three study regions. The mean values of the magnitude of the normalized delay time range from 0.005 s/km to 0.007 s/km and to 0.009 s/km, respectively for the L'Aquila (AQU) area, the High Tiber Valley (ATF) and the Val d'Agri (VA), suggesting a 3-4% of crustal anisotropy. In each area are also examined the spatial and temporal distribution of anisotropic parameters, which lead to some innovative observations, listed below. 1) The higher values of normalized delay times have been observed in those zones where most of the seismic events occur. This aspect was further investigated, by evaluating the average seismic rate, in a time period, between years 2005 and 2010, longer than the lapse of time, analyzed in the anisotropic studies. This comparison has highlighted that the value of the normalised delay time is larger where the seismicity rate is higher. 2) In the Alto Tiberina Fault area the higher values of normalised delay time are not only related to the presence of a high seismicity rate but also to the presence of a tectonically doubled carbonate succession. Therefore, also the lithology, plays a important role in hosting and preserving the micro-fracture network responsible for the anisotropic field. 3) The observed temporal variations of anisotropic parameters, have been observed and related to the fluctuation of pore fluid pressure at depth possibly induced by different mechanisms in the different regions, for instance, changes in the water table level in Val D’Agri, occurrence of the April 6th Mw=6.1 earthquake in L’Aquila.Since these variations have been recognized, it is possible to affirm that the models that better fit the results, both in term of fast directions and of delay times, seems to be EDA and APE models. 2011-09-22T22:00:00Z http://hdl.handle.net/2122/7970 Title: crustal fracturing field and presence of fluid as revealed by seismic anisotropy: case-histories from seismogenic areas in the Apennines Authors: Pastori, Marina; Università degli studi di Perugia Abstract: During the last decades, the study of seismic anisotropy has provided useful information for the interpretation and evaluation of the stress field and active crustal deformation. Seismic anisotropy can yield valuable information on upper crustal structure, fracture field, and presence of fluid-saturated rocks crossed by shear waves. Several studies worldwide demonstrate that seismic anisotropy is related to stress-aligned, filled-fluid micro-cracks (EDA model, Crampin et al., 1984b; Crampin, 1993). The seismic anisotropy is an almost ubiquitous property of the Earth and the Shear Wave Splitting is the most unambiguous indicator of anisotropy, but the automatic estimation of the splitting parameters is difficult because the effect of the anisotropy on a seismogram is a second order, not easily detectable effect. Different researchers developed automated techniques aimed to study the Shear Wave Splitting: in this study, the results of different codes are compared in order to evaluate the best method for automatic anisotropy evaluation. In the last three years, an automatic analysis code, “Anisomat+”, was developed, tested and improved to calculate the anisotropic parameters: fast polarization direction () and delay time (∂t). “Anisomat+” consists of a set of MatLab scripts able to retrieve automatically crustal anisotropy parameters from three-component seismic recordings of local earthquakes. It needs waveforms and hypocentral parameters in the format routinely archived by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The code uses horizontal component cross-correlation method: a mathematical algorithm aimed to measure the similarity of the pulse shape between two shear waves. Anisomat+ has been compared to other two automatic analysis codes (SPY and SHEBA) and tested on three zones of the Apennines (Val d’Agri, Tiber Valley and L’Aquila surroundings). It was observed that, if the number of measures is large enough, at each station the average values of the parameters (fast direction and delay time) are comparable. The main goal in developing of an automatic code was to have tool able to work on a big amount of data, in a short time, by reducing the errors due to the subjectivity. These two acquirements are very useful and are the basis to develop a quasi real-time monitoring of the anisotropic parameters. The anisotropic parameters, resulting from the automatic computation, have been interpreted to determine the fracture field geometries; for each area, I defined the dominant fast direction and the intensity of the anisotropy, interpreting these results in the light of the geological and structural setting and of two anisotropic interpretative models, proposed in the literature. In the first one, proposed by Zinke and Zoback (2000), the local stress field and cracks are aligned by tectonics phases and are not necessarily related to the presently active stress field. Therefore the anisotropic parameters variations are only space-dependent. In the second, EDA model (Crampin, 1993), and its development in the APE model (Zatsepin and Crampin, 1995) fluid-filled micro-cracks are aligned or ‘opened’ by the active stress field and the variation of the stress field might be related to the evolution of the pore pressure in time; therefore in this case the variation of the anisotropic parameters are both space- and time- dependent. I recognized that the average of fast directions, in the three selected areas, are oriented NW-SE, in agreement with the orientation of the active stress field, as suggested by the EDA model, proposed by Crampin (1993), but also, by the proposed by Zinke and Zoback model; in fact, NW-SE direction corresponds also to the strike of the main fault structures in the three study regions. The mean values of the magnitude of the normalized delay time range from 0.005 s/km to 0.007 s/km and to 0.009 s/km, respectively for the L'Aquila (AQU) area, the High Tiber Valley (ATF) and the Val d'Agri (VA), suggesting a 3-4% of crustal anisotropy (Piccinini et al., 2006). In each area are also examined the spatial and temporal distribution of anisotropic parameters, which lead to some innovative observations, listed below. o The higher values of normalized delay times have been observed in those zones where most of the seismic events occur. This aspect was further investigated, by evaluating the average seismic rate, in a time period, between years 2005 and 2010, longer than the lapse of time, analyzed in the anisotropic studies. This comparison has highlighted that the value of the normalised delay time is larger where the seismicity rate is higher. o In the Alto Tiberina Fault area the higher values of normalised delay time are not only related to the presence of a high seismicity rate but also to the presence of a tectonically doubled carbonate succession. Therefore, also the lithology, plays a important role in hosting and preserving the micro-fracture network responsible for the anisotropic field. o The observed temporal variations of anisotropic parameters, have been observed and related to the fluctuation of pore fluid pressure at depth possibly induced by different mechanisms in the different regions, for instance, changes in the water table level in Val D’Agri (Valoroso et al., GJI submitted), occurrence of the April 6th Mw=6.1 earthquake in L’Aquila (Lucente et al., 2010). Since these variations have been recognized, it is possible to affirm that the models that better fit my results, both in term of fast directions and of delay times, seems to be those proposed by Crampin (1993) and Zatsepin & Crampin (1995), respectively EDA and APE models. 2011-02-16T23:00:00Z