Search

We study whether the shallow volcanic seismic tremors related to the bradyseism observed at the Phlegraean Fields (Campi Flegrei, Pozzuoli, and Naples) from 2008 to 2020 by the Osservatorio Vesuviano could be partially triggered by local rainfall events. We use the daily rainfall record measured at the nearby Meteorological Observatory of San Marcellino in Naples and develop two empirical models to simulate the local seismicity starting from the hypothesized rainfall-water effect under different scenarios. We found statistically significant correlations between the volcanic tremors at the Phlegraean Fields and our rainfall model during years of low bradyseism. More specifically, we observe that large amounts and continuous periods of rainfall could trigger, from a few days to 1 or 2 weeks, seismic swarms with magnitudes up to M = 3. The results indicate that, on long timescales, the seismicity at the Phlegraean Fields is very sensitive to the endogenous pressure from the deep magmatic system causing the bradyseism, but meteoric water infiltration could play an important triggering effect on short timescales of days or weeks. Rainfall water likely penetrates deeply into the highly fractured and hot shallow-water-saturated subsurface that characterizes the region, reduces the strength and stiffness of the soil and, finally, boils when it mixes with the hot hydrothermal magmatic fluids migrating upward. The structural collapse of the saturated fractured soil and the mixing of the meteoric fluid with the hot deep fluids triggers the local seismic activity.

We analyze hourly seismic data measured at the Osservatorio Vesuviano Ovest (OVO, 1972-2014) and at the Bunker Est (BKE, 1999-2014) stations on the Mt. Vesuvius. The OVO record is complete for seismic events with magnitude M > 1.9. We demonstrate that before 1996 this record presents a daily oscillation that nearly vanishes afterwards. To determine whether a daily oscillation exists in the seismic activity of the Mt. Vesuvius, we use the higher quality BKE record that is complete for seismic events with magnitude M > 0.2. We demonstrate that BKE confirms that the seismic activity at the Mt. Vesuvius is higher during nighttime than during day-time. The amplitude of the daily oscillation is enhanced during summer and damped during winter. We speculate possible links with the cooling/warming diurnal cycle of the volcanic edifice, with external geomagnetic field and with magnetostriction that should also stress the rocks. We find that the amplitude of the seismic daily cycle changes in time and has been increasing since 2008. Finally, we propose a seismic activity index to monitor the 24-hour oscillation that could be used to complement other methodologies currently adopted to determine the seismic status of the volcano and to prevent the relative hazard., 31 pages, 10 figures, 9 tables

By applying fractal geometry analysis to the drainage network of three large watercourses in America and Europe, we have calculated for the first time their fractal dimension. The aim is to interpret the geomorphologic characteristics to better understand the morphoevolutionary processes of these fluvial morphotypes; to identify and discriminate geomorphic phenomena responsible for any difference or convergence of a fractal dimension; to classify hydrographic patterns, and finally to compare the fractal degree with some geomorphic-quantitative indexes. The analyzed catchment of Russian (California, USA), Ebro (Spain), and Volturno (Italy) rivers are situated in Mediterranean-climate regions sensu Ko¨ppen, but with different geologic context and tectonic styles. Results show fractal dimensions ranging from 1.08 to 1.50. According to the geological setting and geomorphic indexes of these basins, the lower fractal degree indicates a prevailing tectonics, active or not, while the higher degree indicates the stronger erosion processes on inherited landscapes.

The El Nino phenomenon is the Earth’s strongest climatic fluctuation on an interannual timescale and has a quasi-global impact, although originating in the tropical Pacific Ocean. A very strong El Nino is recognized to cause extreme dryness and wetness in different parts of the world. We show that all the eight well-documented influenza pandemics, starting from the first certain one documented in ad 1580, originated in China and in Russia, a few years after the occurrence of a very strong or after a prolonged strong/moderate El Nino event. At present, the next El Nino will probably occur at the beginning of 2013 (Mazzarella et al. Theor Appl Climatol 100:23–27, 2010), and this forecast may suggest to be well prepared to take appropriate precautionary epidemiological measures.

Two strong heat waves in the summer of 2003 determined elevated heat discomfort conditions all across the Western Europe. In this context, the analysis of hourly Heat Index values in the city of Naples (Southern Italy) showed prolonged heat discomfort conditions during the second half of June 2003 and from the second half of July 2003 up to the first week of September 2003, resulting in highest mortality rate for persons 75 years or more.

The floods that have occurred in the upper valley of the Po river (northern Italy) were classified according to an index of strength on the basis of documentary sources available at the meteorological observatory of Moncalieri since 1780. The catalogue was ascertained to be complete only for events classified at least as moderate. Application of Cantor dust statistics and rank-ordering statistics to time-occurrences of floods provided significant evidence of scale-invariance laws that might be very helpful in assessing and reducing future hazards. The increase in the fractal dimension for floods occurring after 1890 is here related to the significant increase in the number of very heavy rainfall episodes measured all over Italy.

Here we study the Arctic and Antarctic sea-ice area records provided by the National Snow and Ice Data Center (NSIDC). These records reveal an opposite climatic behavior: since 1978 the Arctic sea-ice area index decreased, that is, the region has warmed, while the Antarctic sea-ice area index increased, that is, the region has cooled. During the last 7 years the Arctic sea-ice area has stabilized while the Antarctic sea-ice area has increased at a rate significantly higher than during the previous decades; that is, the sea-ice area of both regions has experienced a positive acceleration. This result is quite robust because it is confirmed by alternative temperature climate indices of the same regions. We also found that a significant 4-5-year natural oscillation characterizes the climate of these sea-ice polar areas. On the contrary, we found that the CMIP5 general circulation models have predicted significant warming in both polar sea regions and failed to reproduce the strong 4-5-year oscillation. Because the CMIP5 GCM simulations are inconsistent with the observations, we suggest that important natural mechanisms of climate change are missing in the models.

The up^down motion at Campi Flegrei may be due to the internal dynamics of the system and does not necessarily require a push, such as a new input of magma, from outside. The different eruptive phases which have occurred at Campi Flegrei might be related to deterministic chaotic magma flows, similar to those studied in simple experimental systems and theoretically well schematized by the so-called Lorenz equations. Here, different convective cells are hypothesized to operate at decreasing time and spatial scales; they are found to reasonably explain the volcanic history of Campi Flegrei starting from the Campanian Ignimbrite phase, through the Yellow Tuff, up to the Monte Nuovo event and the recent bradyseismic crises. 3 2002 Elsevier Science B.V. All rights reserved.

The volcanic seismicity occurring in Campi Flegrei during the 1983–1984 volcanic crisis is quantitatively analyzed by means of fractal (scale invariant) geometry in all its five dimensional set (magnitude, time and space). The significant power laws, relating the number of earthquakes to magnitude, time and space, within a limited range of scales, show that the Campi Flegrei region is in a critical state during the whole crisis.

Selected records from hundreds of raingauges located along the river basins of the largest Italian rivers, throughout the whole of Italy, show a fairly similar interannual variability. Analysis of the historical time series of these data determined very significant 11-yr, 22-yr and 44-yr variabilities that are possibly linked to coherent fluctuations in the high-speed solar wind precipitation into the atmosphere. The combined effect of such signals is found to explain 60% of the yearly rainfall variance.

Volcanic events have been, up to now, traditionally predicted through deterministic or probabilistic linear methods. Here a new non-linear approach is carried out, based on artificial neural networks (ANN), a non-linear physical mathematical model to interconnect data emulating animal brain behaviour. Being an artificial intelligence system, this model is able, once both the observed data records and starting values of the network’s parameters have been entered, to self-guide itself and supply the best outputs with respect to the input parameters. On varying the starting values, the exit values change too, the degree of improvement being measurable quantitatively. This model has been applied to four different volcanoes (Vesuvius, Phlegraean Fields, Etna, Hawaii) with different volcanic characteristics, in order to measure the effectiveness of the method as a general one. For this purpose, data regarding seismicity or ground displacements (vertical, radial, tangential components) were processed and predicted by means of ANN. The results are encouraging and, in many cases, in very fair agreement with the observed data.

At Vesuvius, the intervals between final effusive eruptions since 1631 AD and those between successive plinian eruptions since 25 000 yr BP follow the same power law, when separately ranked in decreasing order. So, shifts from small to large scales are possible and this might be very helpful for the assessment of hazards of future strong volcanic activity.

Allo scopo di catturare i processi dinamici non lineari intrinseci al Vesuvio su scale temporali di lungo periodo, si è realizzato un sistema ibrido costituito da una Rete Neurale Artificiale di tipo Multi-Layer Perceptron e da un Algoritmo Evolutivo di tipo Breeder, e lo si è applicato alla ben documentata attività eruttiva esibita dal Vesuvio a partire dal 1631, in termini di serie temporale del Volcanic Explosivity Index (VEI). I valori previsti dal sistema nel periodo di train e in quello di test ben si adattano a quelli storici.

The catalogue of eruptions occurring at Vesuvio during the period 1631–1944 is shown to be complete for the range Volcanic Explosivity Index (VEI) between 1.5 and 4.0. The time clustering of eruptive events, as indicated by the catalogue, shows a fractal dimension and a scaling region largely dependent on VEI. This might reflect the turbulence of the magma flowing under the volcano which is responsible for cascading of energy from large to small eddies.

The digitized lava-flow margins of well-defined extended eruptions occurring at Vesuvio in 1760, 1794, 1861, 1906, 1929 and 1944 are found to follow fractal behaviours inside a scaling region enclosed between 50 and 400 m. Although the invariance region is well respected, the fractal dimension D varies from one lava flow to another: the more irregular the lava-flow margin, the larger the value of D. The ascertained dependence of D on the duration of premonitory activity, preceding the emission of lavas, might provide some insight into the inner volcanic processes before the eruption and into the dynamical processes operating during flow emplacement.

The catalogue of volcanic earthquakes recorded at Vesuvio (1972–1993) is shown to be complete for events with magnitude enclosed between 1.8 and 3.0. Such a result is converted in significant fractal laws (power laws) relating the distribution of earthquakes to the distribution of energy release, seismic moment, size of fractured zone and linear dimension of faults. The application of the Cantor dust model to time sequence of Vesuvio seismic and eruptive events allows the determination of significant time-clustering fractal structures. In particular, the Vesuvio eruptive activity shows a double-regime process with a stronger clustering on short-time scales than on long-time scales. The complexity of the Vesuvio system does not depend on the number of geological, geophysical and geochemical factors that govern it, but mainly on the number of their interconnections, on the intensity of such linkages and on the feed-back processes. So, all the identified fractal features are taken as evidence that the Vesuvio system is in a self-organized critical state i.e., in a marginally stable state in which a small perturbation can start a chain reaction that can lead to catastrophe. After the catatrophe, the system regulates itself and begins a new cycle, not necessarily periodic, that will end with a successive catastrophe. The variations of the fractal dimension and of the specific scale ranges, in which the fractal behaviour is found to hold, serve as possible volcanic predictors reflecting changes of the same volcanic process.

An 11-yr modulation of worldwide large volcanic and seismic activity has been successfully identified and significantly linked to sunspot activity, using cross-spectral analysis.