Self-sustained oscillator as a model for explosion quakes at Stromboli Volcano

International audienceWe analyze seismic signals produced by explosion-quakes at Stromboli Volcano. We use standard nonlinear procedures to search a low-order effective dynam-ics. The dimension of the reconstructed phase space depends on the number of samples. Namely larger time lengths cor-respond to dynamical systems of different complexity. If we restrict the analysis to the signal associated directly to the source (Chouet et al., 1997), we obtain a phase space dimen-sion equal to two. We reproduce this part of the signal with a simple single self-sustained oscillator

Characterization of GPS time series at the Neapolitan volcanic area by statistical analysis

The GPS time series recorded at the Neapolitan volcanic area reveals a very peculiar behavior. When a clear deformation is observed, the amplitude distribution evolves from a super‐Gaussian to a broader distribution. This behavior can be characterized by evaluating the kurtosis. Spurious periodic components were evidenced by independent component analysis and then removed by filtering the original signal. The time series for all stations was modeled with a fifth‐order polynomial fit, which represents the deformation history at that place. Indeed, when this polynomial is subtracted from the time series, the distributions again become super‐Gaussian. A simulation of the deformation time evolution was performed by superposing a Laplacian noise and a synthetic deformation history. The kurtosis of the obtained signals decreases as the superposition increases, enlightening the insurgence of the deformation. The presented approach represents a contribution aimed at adding further information to the studies about the deformation at the Neapolitan volcanic area by revealing geologically relevant data

ANALISI DELLE COMPONENTI INDIPENDETI (ICA) NELLO STUDIO DELLE DEFORMAZIONI DEL SUOLO IN AREE VULCANICHE

Independent component analysis (ICA) is a recent and well-known technique used to separate mixtures of signals. This technique has been applied to the ground deformation time-series recorded at the permanent GPS network of the Osservatorio Vesuviano-INGV in order to characterize the deformation background level in the Neapolitan volcanic area. The analysis revealed the presence of five independent periodic signals common at all the GPS stations; some of them are interpreted as effects of earth tides. The residual signal at each station represent the local ground deformation. Unfortunately the ICA cannot provide the absolute amplitude of the components, indeed we are not able to obtain a residual amplitude at each station. Then we used a stationarity analysis in order to investigate the eventual presence of local transient deformations. The ICA technique combined with the stationarity analysis has shown to be a very interesting tool for individuating ground deformation trends and could be very useful in volcanic areas monitoring

Spatial and temporal distribution of vertical ground movements at Mt. Vesuvius in the period 1973-2009

Since the early ’70s vertical ground movements at Mount Vesuvius area have been investigated and monitored by the Osservatorio Vesuviano (Istituto Nazionale di Geofisica Vulcanologia - Osservatorio Vesuviano since 2001). This monitoring began with the installation of a high-precision leveling line in the region at medium-high elevations on the volcano. The deformation pattern and expected strain field assessment methods in the volcanic structure induced by inner sources has demanded in subsequent years the expansion of the leveling network up to cover the whole volcanic area, enclosing part of leveling lines of other institutions. As a result of this expansion, the Mt. Vesuvius Area Leveling Network (VALN) has today reached a length of about 270 km and consists of 359 benchmarks. It is configured in 21 circuits and is connected, westward, to the Campi Flegrei leveling network and, northward, to the Campania Plain leveling network. The data collected have been carefully re-analyzed for random and systematic errors and for error propagation along the leveling lines to identify the areas affected by significant ground movements. For each survey, the data were rigorously adjusted and vertical ground movements were evaluated by differentiating the heights calculated by the various measurements conducted by the Osservatorio Vesuviano from 1973 to 2009

Universality in solar flare and earthquake occurrence

Earthquakes and solar flares are phenomena involving huge and rapid releases of energy characterized by complex temporal occurrence. By analysing available experimental catalogs, we show that the stochastic processes underlying these apparently different phenomena have universal properties. Namely both problems exhibit the same distributions of sizes, inter-occurrence times and the same temporal clustering: we find afterflare sequences with power law temporal correlations as the Omori law for seismic sequences. The observed universality suggests a common approach to the interpretation of both phenomena in terms of the same driving physical mechanism

Magnusiomyces clavatus infection in a child after allogeneic hematotopoetic stem cell transplantation: Diagnostic and therapeutic implications

Magnusiomyces clavatus is an ascomycetous fungus causing invasive disease in immuno-compromised patients. Neutropenia, contaminated venous catheters, previous antifungal treatment are risk factors for this infection. We report a case of Magnusiomyces clavatus fungemia with pulmonary, renal and skin localizations in a 6-year-old boy with prolonged neutropenia because of three allogeneic hematopoietic stem cell transplantations. The infection was controlled by aggressive and strictly monitored combination therapy with voriconazole and liposomial-ampthotericine-B along with durable recover from neutropeni

The Corinth Rift Laboratory, Greece (CRL): A Multidisciplinary Near Fault Observatory (NFO) on a Fast Rifting System

The western rift of Corinth (Greece) is one of the most active tectonic structures of the euro-mediterranean area. Its NS opening rate is 1.5 cm/yr ( strain rate of 10-6/yr) results into a high microseismicity level and a few destructive, M>6 earthquakes per century, activating a system of mostly north dipping normal faults. Since 2001, monitoring arrays of the European Corinth Rift Laboratory (CRL, www.crlab.eu) allowed to better track the mechanical processes at work, with short period and broad band seismometers, cGPS, borehole strainmeters, EM stations, …). The recent (300 kyr) tectonic history has been revealed by onland (uplifted fan deltas and terraces) and offshore geological studies (mapping, shallow seismic, coring), showing a fast evolution of the normal fault system. The microseismicity, dominated by swarms lasting from days to months, mostly clusters in a layer 1 to 3 km thick, between 6 and 9 km in depth, dipping towards north, on which most faults are rooting. The diffusion of the microseismicity suggests its triggering by pore pressure transients, with no or barely detected strain. Despite a large proportion of multiplets, true repeaters seem seldom, suggesting a minor contribution of creep in their triggering, although transient or steady creep is clearly detected on the shallow part of some majors faults. The microseismic layer may thus be an immature, downward growing detachment, and the dominant rifting mechanism might be a mode I, anelastic strain beneath the rift axis , for which a mechanical model is under development. Paleoseismological (trenching, paleoshorelines, turbidites), archeological and historical studies completed the catalogues of instrumental seismicity, motivating attempts of time dependent hazard assessment. The Near Fault Observatory of CRL is thus a multidisciplinary research infrastructure aiming at a better understanding and modeling of multiscale, coupled seismic/aseismic processes on fault systems.Grant for Researchers (CC) ID 188753

THE CHAOTICITY DEGREE OF THE CAMPI-FLEGREI SEISMICITY, SOUTHERN ITALY

In the present paper we use the general technique of Grassberger & Procaccia (1983) which allows us t o reconstruct the phase space of the seismicity at Campi Flegrei from its time series and quantify the degree of chaoticity of such seismicity. W e find that the seismic energy released in the Campi Flegrei area as a function of time does not exhibit a chaotic behaviour. On the contrary we determine that this phenomenon is quasi-periodic with fundamental periods of about 1.3 and 0.3 weeks

On-Off Intermittency in Earthquakes Occurrence

The clustered occurrence of earthquakes is viewed as an intermittent phenomenon, interpreting the clusters of events as chaotic bursts combined to the Poissonian occurrence of background seismicity. In particular, we suggest that it can be interpreted as an example of on-off intermittency. This kind of intermittency is parameter driven and exhibits certain universal statistical properties. The study of a Californian catalogue allows to interpret earthquake occurrence as an on-off intermittent phenomenon. Our results suggest the existence of a branching mechanism in earthquake occurrence well explained by epidemic type models