Investigating the spatial variability of the time-scaling properties in Italian seismicity

International audienceSignificant power-law long-range correlated structures have been identified in the Italian seismicity from 1983 to 2003. We performed the Allan Factor Analysis and the Detrended Fluctuation Analysis on both the full and the aftershock-depleted seismic data, extracted by the INGV (National Institute of Geophysics and Volcanology) instrumental catalog.Our findings suggest that (i) the time-scaling behaviour characterizes mainly the Apennine chain; (ii) the time-correlated behaviour of the seismicity is persistent, and this implies that the dynamics underlying the seismic phenomenology is characterized by the presence of "positive feedback mechanisms"; (iii) significant time correlation is not simply related with the mainshock/aftershock mechanisms

Multifractal variability in geoelectrical signals and correlations with seismicity: a study case in southern Italy

International audienceMultifractal fluctuations in the time dynamics of geoelectrical data, recorded in a seismic area of southern Italy, have been revealed using the Multifractal Detrended Fluctuation Analysis (MF-DFA), which allows to detect multifractality in nonstationary signals. Our findings show that the geoelectrical time series, recorded in the seismic area of southern Apennine Chain (Italy), is multifractal. The time evolution of the multifractality suggests that the multifractal degree increases prior the occurrence of earthquakes. This study aims to propose another approach to investigate the complex dynamics of earthquake-related geoelectrical signals

Fisher Information Analysis of earthquake-related geoelectrical signals

International audienceWe studied the time fluctuations in the dynamics of geoelectrical data, recorded in Tito site, which is located in a seismic area of southern Italy. We used the Fisher Information Measure, which is a powerful tool to investigate complex and nonstationary signals. The time evolution of the Fisher Information Measure calculated for our signal reveals links with the earthquakes occurring in the investigated area

Vertical dipoles to detect self potential signals in a seismic area of southern Italy: Tito station

International audienceSince 2000 the Institute of Methodologies for the Environmental Analysis (National Council of Research, Tito, Italy) installed a geophysical monitoring network able to detect geoelectric, geochemic and seismometric parameters in seismic areas of southern Italy. During this period a very large data-base of geophysical time series has been organized and it is actually available to assess robust statistical methodologies to identify geophysical anomalous patterns linked with local seismicity. To better understand the influence of rain and cultural noise on geoelectrical signals (Self Potential), during May 2004 we drilled in Tito station a 20 m-depth hole to measure the SP vertical component. The array is characterized by five Pb-PbCl2 electrodes put at different depths. The common electrode is fixed at 20 m. In this work we present some electrical anomalies probably correlated with local seismic activity on vertical dipoles recorded in Tito station

Principal component analysis of geoelectrical signals measured in the seismically active area of Basilicata Region (southern Italy)

International audienceGeoelectrical fluctuations are the end product of several geophysical phenomena. In particular geoelectrical signals measured in seismically active areas can be attributed to stress and strain changes, associated with earthquakes. The complexity of this problem has suggested the development of advanced statistical methods to investigate the heterogeneous nature of these fluctuations. In this paper we analysed the time dynamics of short-term variability of geoelectrical field measured at Giuliano station, located in Basilicata Region, one of the most seismically active areas of southern Italy. We applied the principal component analysis (PCA). The analysis has shown earthquake precursory patterns in the daily variation of the principal components, revealing that the PCA approach is promising for monitoring seismic areas

MONOFRACTAL AND MULTIFRACTAL ANALYSIS IN SHORT - TERM TIME DYNAMICS OF ULF GEOMAGNETIC FIELD MEASURED IN CRETE, GREECE

In this work, a monofractal and multifractal characterization of the short-term time dynamical fluctuations of the ultra low frequency (ULF) geomagnetic field, measured by one station installed in Creete, Greece, has been carried out. Time scale properties of the three ULF geomagnetic components, two horizontal (x, y) and one vertical (z) have been analyzed through the power spectral density, Higuchi method and Hurst R/S analysis. Results point out the presence of fractal features expressing long-range time correlation with scaling coefficients, which are the clue of persistent mechanism. Using a set of multifractal parameters, defined from the shape of the multifractal spectrum, it has been observed that the degree of multifractality, that characterizes the original signals, is "weaker" if compared to the residual signals, obtained from the original ones after removing the four observed periodicities (24-, 12-, 8- and 6-h periodicties). Furthermore the horizontal χ and y components have revealed to be less multifractal than the vertical z-component

Multifractality in local geomagnetic field at Etna volcano, Sicily (southern Italy)

International audienceWe applied the Multifractal Detrended Fluctuation Analysis (MF-DFA), which allows to detect multifractality in nonstationary signals, to the hourly means of local geomagnetic field recorded at Mt. Etna volcano (southern Italy). We studied the signal measured at one geomagnetic station, installed at the summit of volcano, which was characterized by a strong eruption on 27 October 2002. We analyzed two frames of signals, one measured before the eruption and the other after, in order to evaluate dynamical changes induced by the eruptive event. Our findings show that: i) the geomagnetic time series is multifractal; ii) the multifractal degree of the signal decreases after the occurrence of eruption. This study aims to propose another approach to investigate the complex dynamics of volcano-related geomagnetic field

A preliminary studyof the site-dependence of the multifractalfeatures of geoelectric measurements

Multifractal analysis was performed to characterize the fluctuations in dynamics of the hourly time variability of self-potential signals measured from January 2001 to September 2002 by three stations installed in the Basilicata region (Southern Italy). Two stations (Giuliano and Tito) are located in a seismic area, and one (Laterza) in an aseismic area. Multifractal formalism leads to the identification of a set of parameters derived from the shape of the multifractal spectrum (the maximum a0, the asymmetry B and the width W) and measuring the «complexity» of the signals. Furthermore, the multifractal parameters seem to discriminate self-potential signals measured in seismic areas from those recorded in aseismic areas

Investigating correlations between earthquakes and extreme eventsin self-potential data recorded in a seismicarea of Southestern Appennine Chain (Italy)

The Normalized Wavelet Cross-Correlation Function (NWCCF) was used to study correlations between the series of extreme events in self-potential data and earthquakes, both modelled as stochastic point processes. This method gives objective results, robust to the presence of nonstationarities that often affect observational time series. Furthermore, the NWCCF identifies the timescales involved in the cross-correlated behaviour between two point processes. In particular, we analyzed the cross-correlation between the sequence of extreme events in selfpotential data measured at the monitoring station Tito, located in a seismic area of Southern Italy, and the series of earthquakes which occurred in the same area during 2001. To evaluate the influence of rain on the dynamics of geoelectrical variations, we applied the same approach between the selected extreme values and the rain data. We find that the anomalous geoelectrical values seem to cross-correlate with the rain at short and intermediate timescales (t< 500 h), while they significantly cross-correlate only with earthquakes (M = 2.5) at long timescales (t> 500 h)

Magnetic and ground penetrating radar for the research of Medieval buried structures in Marche Region

A magnetic and Ground Penetrating Radar joint survey was carried out in the framework of the R.I.M.E.M. project that has the aim of supporting the archaeological prospections and drive the selection of the excavation areas related to the Late Roman Period and Early Middle Ages in the Central and Southern Italy. In particular, this papers deals with the magnetic surveys acquired near “Madonna della Valle” and GPR and magnetic joint surveys carried out in “Monastero”site. Most of magnetic maps carried out in “Madonna della Valle” site shown the absence of structured magnetic anomalies, despite of the presence of archaeological signs. Several hypothesis were given to explain this evidence. Joint interpretation performed in “Monastero” site shown more intense magnetic anomalies related with shallower reflections due to probably to buried pipes. Other reflections are related with magnetic anomalies compatible with archaeological targets, but some significant reflections do not correspond to any magnetic anomaly, indicating magnetic method could be “blind” respect the archaeological target. New field surveys including the electrical resistivity tomography could be carried out in order to overcome these acquisition and interpretation difficulties