Showing papers in "Annals of Geophysics in 2011"
TL;DR: In this paper, the analytic expression of a linear dissipative mechanism whose Q is almost frequency independent over large frequency ranges was obtained by introducing fractional derivatives in the stress strain relation.
Abstract: Laboratory experiments and field observations indicate that tlie Q of many non ferromagnetic inorganic solids is almost frequency independent in the range 10' to 10~2 cps; although no single substance has been investigated over the entire frequency spectrum. One of the purposes of this investigation is to find the analytic expression of a linear dissipative mechanism whose Q is almost frequency independent over large frequency ranges. This will be obtained by introducing fractional derivatives in the stress strain relation. Since the aim of this research is to also contribute to elucidating the dissipating mechanism in the earth free modes, we shall treat the cases of dissipation in the free purely torsional modes of a shell and the purely radial vibration of a solid sphere. The theory is checked with the new values determined for the Q of the spheroidal free modes of the earth in the range between 10 and 5 minutes integrated with the Q of the Railegh waves in the range between 5 and 0.6 minutes. Another check of the theory is made with the experimental values of the Q of the longitudinal waves in an alluminimi rod, in the range between 10-5 and 10-3 seconds. In both clicks the theory represents the observed phenomena very satisfactory.
515 citations
TL;DR: In this article, the authors focus on the short-term prediction and forecasting of tectonic earthquakes and indicate guidelines for utilization of possible forerunners of large earthquakes to drive civil protection actions, including the use of probabilistic seismic hazard analysis in the wake of a large earthquake.
Abstract: Following the 2009 L'Aquila earthquake, the Dipartimento della Protezione Civile Italiana (DPC), appointed an International Commission on Earthquake Forecasting for Civil Protection (ICEF) to report on the current state of knowledge of short-term prediction and forecasting of tectonic earthquakes and indicate guidelines for utilization of possible forerunners of large earthquakes to drive civil protection actions, including the use of probabilistic seismic hazard analysis in the wake of a large earthquake. The ICEF reviewed research on earthquake prediction and forecasting, drawing from developments in seismically active regions worldwide. A prediction is defined as a deterministic statement that a future earthquake will or will not occur in a particular geographic region, time window, and magnitude range, whereas a forecast gives a probability (greater than zero but less than one) that such an event will occur. Earthquake predictability, the degree to which the future occurrence of earthquakes can be determined from the observable behavior of earthquake systems, is poorly understood. This lack of understanding is reflected in the inability to reliably predict large earthquakes in seismically active regions on short time scales. Most proposed prediction methods rely on the concept of a diagnostic precursor; i.e., some kind of signal observable before earthquakes that indicates with high probability the location, time, and magnitude of an impending event. Precursor methods reviewed here include changes in strain rates, seismic wave speeds, and electrical conductivity; variations of radon concentrations in groundwater, soil, and air; fluctuations in groundwater levels; electromagnetic variations near and above Earth's surface; thermal anomalies; anomalous animal behavior; and seismicity patterns. The search for diagnostic precursors has not yet produced a successful short-term prediction scheme. Therefore, this report focuses on operational earthquake forecasting as the principle means for gathering and disseminating authoritative information about time-dependent seismic hazards to help communities prepare for potentially destructive earthquakes. On short time scales of days and weeks, earthquake sequences show clustering in space and time, as indicated by the aftershocks triggered by large events. Statistical descriptions of clustering explain many features observed in seismicity catalogs, and they can be used to construct forecasts that indicate how earthquake probabilities change over the short term. Properly applied, short-term forecasts have operational utility; for example, in anticipating aftershocks that follow large earthquakes. Although the value of long-term forecasts for ensuring seismic safety is clear, the interpretation of short-term forecasts is problematic, because earthquake probabilities may vary over orders of magnitude but typically remain low in an absolute sense (< 1% per day). Translating such low-probability forecasts into effective decision-making is a difficult challenge. Reports on the current utilization operational forecasting in earthquake risk management were compiled for six countries with high seismic risk: China, Greece, Italy, Japan, Russia, United States. Long-term models are currently the most important forecasting tools for civil protection against earthquake damage, because they guide earthquake safety provisions of building codes, performance-based seismic design, and other risk-reducing engineering practices, such as retrofitting to correct design flaws in older buildings. Short-term forecasting of aftershocks is practiced by several countries among those surveyed, but operational earthquake forecasting has not been fully implemented (i.e., regularly updated and on a national scale) in any of them. Based on the experience accumulated in seismically active regions, the ICEF has provided to DPC a set of recommendations on the utilization of operational forecasting in Italy, which may also be useful in other countries. The public should be provided with open sources of information about the short-term probabilities of future earthquakes that are authoritative, scientific, consistent, and timely. Advisories should be based on operationally qualified, regularly updated seismicity forecasting systems that have been rigorously reviewed and updated by experts in the creation, delivery, and utility of earthquake information. The quality of all operational models should be evaluated for reliability and skill by retrospective testing, and they should be under continuous prospective testing against established long-term forecasts and alternative time-dependent models. Alert procedures should be standardized to facilitate decisions at different levels of government and among the public. Earthquake probability thresholds should be established to guide alert levels based on objective analysis of costs and benefits, as well as the less tangible aspects of value-of-information, such as gains in psychological preparedness and resilience. The principles of effective public communication established by social science research should be applied to the delivery of seismic hazard information.
363 citations
TL;DR: This work demonstrates how the ObsPy library can be used to develop custom graphical user interface applications and illustrates the general capabilities of ObsPy, and highlights some of its specific aspects that are relevant for seismological data centers and observatories.
Abstract: Data acquisition by seismic centers relies on real-time systems, like SeisComP3, Antelope and Earthworm. However, these are complex systems that are designed for fast and precisely defined standard real-time analyses. Therefore, it is not a simple task to access or modify internal routines, and to integrate them into custom-processing workflows or to perform in-depth data analyses. Often a library is necessary that provides convenient access to data and allows easy control over all of the operations that are to be performed on the data. ObsPy is such a library, which is designed to access and process seismological waveform data and metadata. We use short and simple examples here to demonstrate how effective it is to use Python for seismological data analysis. Then, we illustrate the general capabilities of ObsPy, and highlight some of its specific aspects that are relevant for seismological data centers and observatories, through presentation of real-world examples. Finally, we demonstrate how the ObsPy library can be used to develop custom graphical user interface applications.
185 citations
TL;DR: In this article, an effort is made to improve Benioff's method for investigation of strain release in aftershock sequences, which may be summarized as follows: 1. Earthquake volume increases with magnitude, instead of being constant.
Abstract: An effort is made to improve Benioff's method for investigation of strain release in aftershock sequences. The improvement may be summarized as follows: 1. Earthquake volume increases with magnitude, instead of being constant. A relation is given, relating volume to magnitude. 2. A revised energy-magnitude formula is used. 3. The seismic gain ratio, i. e. the ratio between seismic energy and elastic strain energy, probably increases with magnitude, instead of being constant. Likewise, the ratio of fault plane area of the main shock to the vertical section through the aftershock volume increases with magnitude. 4. The seismic energy density, the elastic strain energy density as well as strain are independent of magnitude. 5. The deformation, i. e. the total strain in the aftershock zone, increases with magnitude at the same rate as seismic energy and volume do. As a consequence of these improvements some earlier published strain release characteristics are reconstructed, this time as deformation characteristics instead.
101 citations
TL;DR: In comparison with the great number of disastrous earthquakes which have occurred from antiquity to the present time in Greece, largetsunamis are very rare on the coasts of Greece.
Abstract: In comparison with the great number of disastrous earthquakeswhich have occurred from antiquity to the present time in Greece, largetsunamis are very rare on the coasts of Greece. A really great tsunamimay have started in the Aegean Sea after the tremendous explosion ofSantorin volcano, which occurred 3370 ± 100 years ago (13). After thedeposit of a layer of pumice 20-30 m thick and the emptying of thevolcanic focus, the roof of the cavern thus formed collapsed. Thecentrai part, consisting of an area of 83 sq km, of the former islandStronghyb tlius became a gigantic caldera 300-400 m deep.Tliere is no evidence indicating whether the cobapse took placegraduaby or ab at once. In the second case a huge tsunami should havestarted greater by far than that generated by the explosion of Krakatoa,on August 27, 1883. At that time depths of 200-300 m were formed bythe sinking (24) of 2/3 of the former island of an area of 33 1/2 sq km.Thus the cavity formed by the explosion of Santorin is about 4 timesgreater than that of the Krakatoa.
85 citations
TL;DR: In this paper, the authors designed and developed a volcano monitoring system that is called HOTSAT, which can elaborate both Moderate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) data.
Abstract: Spaceborne remote sensing of high-temperature volcanic features offers an excellent opportunity to monitor the onset and development of new eruptive activity. To provide a basis for real-time response during eruptive events, we designed and developed the volcano monitoring system that we call HOTSAT. This multiplatform system can elaborate both Moderate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) data, and it is here applied to the monitoring of the Etna volcano. The main advantage of this approach is that the different features of both of these sensors can be used. It can be refreshed every 15 min due to the high frequency of the SEVIRI acquisition, and it can detect smaller and/or less intense thermal anomalies through the MODIS data. The system consists of data preprocessing, detection of volcano hotspots, and radiative power estimation. To locate thermal anomalies, a new contextual algorithm is introduced that takes advantage of both the spectral and spatial comparison methods. The derivation of the radiative power is carried out at all ‘hot’ pixels using the middle infrared radiance technique. The whole processing chain was tested during the 2008 Etna eruption. The results show the robustness of the system after it detected the lava fountain that occurred on May 10 through the SEVIRI data, and the very beginning of the eruption on May 13 through the MODIS data analysis.
70 citations
TL;DR: In this article, a long time series of fluid pressure and temperature within a hydrothermal system feeding the Solfatara fumaroles are investigated, on the basis of the chemical equilibria within the CO2-H2O-CO gas system, and the agreement between geochemical signals and ground movements of the area (bradyseismic phenomena) suggests a direct relationship between the pressurization process and the ground uplift.
Abstract: Long time series of fluid pressure and temperature within a hydrothermal system feeding the Solfatara fumaroles are investigated here, on the basis of the chemical equilibria within the CO2–H2O–H2–CO gas system. The Pisciarelli fumarole external to Solfatara crater shows an annual cycle of CO contents that indicates the occurrence of shallow secondary processes that mask the deep signals. In contrast, the Bocca Grande and Bocca Nova fumaroles located inside Solfatara crater do not show evidence of secondary processes, and their compositional variations are linked to the temperature–pressure changes within the hydrothermal system. The agreement between geochemical signals and the ground movements of the area (bradyseismic phenomena) suggests a direct relationship between the pressurization process and the ground uplift. Since 2007, the gas geoindicators have indicated pressurization of the system, which is most probably caused by the arrival of deep gases with high CO2 contents in the shallow parts of the hydrothermal system. This pressurization process causes critical conditions in the hydrothermal system, as highlighted by the increase in the fumarole temperature, the opening of new vents, and the localized seismic activity. If the pressurization process continues with time, it is not possible to rule out the occurrence of phreatic explosions.
66 citations
TL;DR: The authors analyzed the structural features of eruptions from 1900 to the present, one of the most active periods in the documented eruptive history of Etna, which comprised 35 summit and 33 flank events.
Abstract: Mount Etna produces frequent eruptions from its summit craters and from fissures on its flanks. The flank fissures trend approximately radially to the summit, and are mainly concentrated in three rift zones that are located on the NE, S and W flanks. Many flank eruptions result from lateral magma transfer from the central conduit into fractures intersecting the flanks, although some eruptions are fed through newly formed conduits that are not directly linked to the central conduit. We analyzed the structural features of eruptions from 1900 to the present, one of the most active periods in the documented eruptive history of Etna, which comprised 35 summit and 33 flank events. Except for a small eruption on the W flank in 1974, all of the flank eruptions in this interval occurred on or near the NE and S rifts. Eruptions in the NE sector were generally shorter, but their fissure systems developed more rapidly and were longer than those in the S sector. In contrast, summit eruptions had longer mean durations, but generally lower effusion rates (excluding paroxysmal events characterized by very high effusion rates that lasted only a few hours). This database was examined considering the main parameters (frequency and strike) of the eruptive fissures that were active over the last ~2 ka. The distribution in time and space of summit and flank eruptions appears to be closely linked to the dynamics of the unstable E to S flank sector of Etna, which is undergoing periodic displacements induced by subvolcanic magma accumulation and gravitational pull. In this framework, magma accumulation below Etna exerts pressure against the unbuttressed E and S flanks, which have moved away from the rest of the volcano. This has caused an extension to the detachment zones, and has facilitated magma transfer from the central conduit into the flanks.
62 citations
TL;DR: A smoothed particle hydrodynamics (SPH) method for lava-flow modeling was implemented on a graphical processing unit (GPU) using the compute unified device architecture (CUDA) developed by NVIDIA, resulting in speed-ups of up to two orders of magnitude.
Abstract: A smoothed particle hydrodynamics (SPH) method for lava-flow modeling was implemented on a graphical processing unit (GPU) using the compute unified device architecture (CUDA) developed by NVIDIA. This resulted in speed-ups of up to two orders of magnitude. The three-dimensional model can simulate lava flow on a real topography with free-surface, non-Newtonian fluids, and with phase change. The entire SPH code has three main components, neighbor list construction, force computation, and integration of the equation of motion, and it is computed on the GPU, fully exploiting the computational power. The simulation speed achieved is one to two orders of magnitude faster than the equivalent central processing unit (CPU) code. This GPU implementation of SPH allows high resolution SPH modeling in hours and days, rather than in weeks and months, on inexpensive and readily available hardware.
56 citations
TL;DR: In this paper, the authors examined long-period seismic records at Umea (Sweden) of an intermediate-depth earthquake in Burma 011 27 February, 1964, exhibit an exceptionally clear case of 8-P conversion at the Mohorovicie discontinuity.
Abstract: Tlie long-period seismic records at Umea (Sweden) of an intermediate-depth earthquake in Burma 011 27 February, 1964, exhibit an exceptionally clear case of 8-P conversion at the Mohorovicie discontinuity. The records are examined from various points of view (arrival times, amplitude ratios, particle motions) and comparisons are made for each test between observations and theory. General aspects of mode conversions at the base of the crust are discussed, both their importance and why they are so seldom observed.
55 citations
TL;DR: In this paper, an approximate relation between the number of aftershocks and the magnitude and focal depth of the main shock has been found, and the probability for an earthquake to be preceded by a large foreshoek not much smaller than the main earthquake is 10%.
Abstract: Deformation characteristics, magnitude and time distribution of the aftershocks of the large earthquakes, occurred in the region of Greece from 1926 till 1964 are investigated. An approximate relation between the number of aftershocks and the magnitude and focal depth of the main shock has been found. Also, an approximate relation has been derived between the magnitude of the largest aftershock and the magnitude and focal depth of the main sliok. The largest aftershock occurs within fourteen days after the main shock. In many cases large " late aftershocks " occur one or more months after the main shock. One or more foreshocks of magnitude larger than 3.5 occurred in forty per cent of the cases. The probability for an earthquake to be preceded l>y a large foreshoek not much smaller than the main shock is 10%. It is shown that some properties of the Earth's material in the aftershock region can be derived by studying the magnitude distribution and deformation characteristics of the aftershocks.
TL;DR: In this article, the authors investigated the time and magnitude distribution of the foreshocks of the Cremasta lake earthquake which occurred on February 5, 1966 and the deformation characteristics and spatial distribution of these shocks.
Abstract: Investigation of the time and magnitude distribution of the fore- and aftershocks of the Cremasta lake earthquake which occurred on February 5, 1966 is made. The deformation characteristics and spatial distribution of these shocks is also studied. Strong evidence is presented that the foreshocks and the main shock have been triggered by the waterloading of the Cremasta artificial lake.
TL;DR: In this paper, the seismic activity in the Greek area is concentrated along the large fault zone bordering the western and southern coasts of Greece, and it is believed that this fault zone marks the trend of a marginai geosyncline, which is now in the course of development in the Eastern Mediterranean.
Abstract: For mapping the seismic activity tlie earthquake energy releaseil per square degree per liundred years was determined, and tlie values obtained were used for drawing isoenergetical lines. Two maps constructed in this way for the periods 1710-1959 and 1841-1959 show clearly tliat the earthquake activity in the Greek area is concentrated, for the most part, along the large fault zone bordering the western and southern coasts of Greece. It is believed tliat this fault zone marks the trend of a marginai geosyncline, which is now in the course of development in the Eastern Mediterranean. Tlie map of earthquake efflciency in Greece sliows clearly tliat the main part of the earthquake energy released in the Greek area comes frolli two well developed centres of higher seismic activity, located along the abovementioned large fault zone.
TL;DR: LAV@HAZARD is a web-based geographic information system that provides an interface for the collection of all of the products coming from the LAVA project research activities, based on Google Maps application programming interface.
Abstract: Satellite data, radiative power of hot spots as measured with remote sensing, historical records, on site geological surveys, digital elevation model data, and simulation results together provide a massive data source to investigate the behavior of active volcanoes like Mount Etna (Sicily, Italy) over recent times The integration of these heterogeneous data into a coherent visualization framework is important for their practical exploitation It is crucial to fill in the gap between experimental and numerical data, and the direct human perception of their meaning Indeed, the people in charge of safety planning of an area need to be able to quickly assess hazards and other relevant issues even during critical situations With this in mind, we developed LAV@HAZARD, a web-based geographic information system that provides an interface for the collection of all of the products coming from the LAVA project research activities LAV@HAZARD is based on Google Maps application programming interface, a choice motivated by its ease of use and the user-friendly interactive environment it provides In particular, the web structure consists of four modules for satellite applications (time-space evolution of hot spots, radiant flux and effusion rate), hazard map visualization, a database of ca 30,000 lava-flow simulations, and real-time scenario forecasting by MAGFLOW on Compute Unified Device Architecture
TL;DR: The present scope of QuakeML 1.2 covers a basic description of seismic events including picks, arrivals, amplitudes, magnitudes, origins, focal mechanisms, and moment tensors.
Abstract: QuakeML is an XML-based data exchange standard for seismology that is in its fourth year of active community-driven development. Its development was motivated by the need to consolidate existing data formats for applications in statistical seismology, as well as setting a cutting-edge, community-agreed standard to foster interoperability of distributed infrastructures. The current release (version 1.2) is based on a public Request for Comments process and accounts for suggestions and comments provided by a broad international user community. QuakeML is designed as an umbrella schema under which several sub-packages are collected. The present scope of QuakeML 1.2 covers a basic description of seismic events including picks, arrivals, amplitudes, magnitudes, origins, focal mechanisms, and moment tensors. Work on additional packages (macroseismic information, ground motion, seismic inventory, and resource metadata) has been started, but is at an early stage. Several applications based on the QuakeML data model have been created so far. Among these are earthquake catalog web services at the European Mediterranean Seismological Centre (EMSC), GNS Science, and the Southern California Earthquake Data Center (SCEDC), and QuakePy, an open-source Python-based seismicity analysis toolkit. Furthermore, QuakeML is being used in the SeisComP3 system from GFZ Potsdam, and in the Collaboratory for the Study of Earthquake Predictability (CSEP) testing center installations, developed by Southern California Earthquake Center (SCEC). QuakeML is still under active and dynamic development. Further contributions from the community are crucial to its success and are highly welcome.
TL;DR: In this article, gas samples collected from fumaroles and bubbling pools at Irruputuncu, Putana, Olca and Alitar volcanoes located in the central Andes volcanic zone (northern Chile).
Abstract: We analyzed gas samples collected from fumaroles and bubbling pools at Irruputuncu, Putana, Olca and Alitar volcanoes located in the central Andes volcanic zone (northern Chile). The Irruputuncu and Putana fumarolic discharges showed outlet temperatures ranging from 83 ˚C to 240 ˚C and from 82 ˚C to 88 ˚C, respectively. The chemical and isotopic ( 3 He/ 4 He, d 13 C-CO 2 , d 18 O-H 2 O and dD-H 2 O) compositions of these discharges were similar to medium-to-high temperature volcanic gases from other active volcanoes in this sector of the Andean volcanic chain (e.g. Lascar volcano). Inorganic and organic gas geothermometers for the H 2 O-CO 2 -CO-H 2 , CO 2 -CH 4 and C 2 -C 3 alkenes-alkanes systems indicated equilibrium temperatures that exceed 500 ˚C at the gas sources. These relatively high temperatures are in agreement with the presence of relevantly high concentrations of magmatic gas emissions, including SO 2 . Olca and Alitar volcano fluid chemistries indicated lower amounts of magmatic-derived gas species, while both the helium and the water isotopic compositions suggested significant fractions of shallow, crustal/meteoric-originated fluids. These indicate contributions from a hydrothermal environment with temperatures <400 ˚C. The geochemical and isotopic features derived from the present study show that the Irruputuncu, Putana, Olca and Alitar volcanoes should be considered as active and thus warrant periodic geochemical monitoring to determine the evolution of these systems and their potential hazards.
TL;DR: The results of geodynamic investigations, in a space of ten years (1953-1963) obtained in the Vajont's gorge during and after construction of the Carlo Semenza dam, are here resumed as mentioned in this paper.
Abstract: The results of geodynamic investigations, in a space of ten years (1953-1963) obtained in the Vajont's gorge during and after construction of the « Carlo Semenza » dam, they are here resumed. On their basis, it is examined the probable reasons of the October 9th 1963 tragic event. It is taken into consideration the seismic activity's awaking -towards the eastern zone of the dam- in the first ten days of September 1965 occurred.
TL;DR: In this article, the authors presented a methodology to validate a long-term hazard map related to lava-flow invasion at Mount Etna, the most active volcano in Europe, using the MAGFLOW cellular automata model.
Abstract: This report presents a retrospective methodology to validate a long-term hazard map related to lava-flow invasion at Mount Etna, the most active volcano in Europe. A lava-flow hazard map provides the probability that a specific point will be affected by potential destructive volcanic processes over the time period considered. We constructed this lava-flow hazard map for Mount Etna volcano through the identification of the emission regions with the highest probabilities of eruptive vents and through characterization of the event types for the numerical simulations and the computation of the eruptive probabilities. Numerical simulations of lava-flow paths were carried out using the MAGFLOW cellular automata model. To validate the methodology developed, a hazard map was built by considering only the eruptions that occurred at Mount Etna before 1981. On the basis of the probability of coverage by lava flows, the map was divided into ten classes, and two fitting scores were calculated to measure the overlap between the hazard classes and the actual shapes of the lava flows that occurred after 1981.
TL;DR: The present study describes the efforts and results obtained by porting the original serial code to the parallel computational platforms offered by modern video cards, and in particular to the NVIDIA Compute Unified Device Architecture (CUDA).
Abstract: The MAGFLOW lava simulation model is a cellular automaton developed by the Sezione di Catania of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and it represents the peak of the evolution of cell-based models for lava-flow simulation. The accuracy and adherence to reality achieved by the physics-based cell evolution of MAGFLOW comes at the cost of significant computational times for long-running simulations. The present study describes the efforts and results obtained by porting the original serial code to the parallel computational platforms offered by modern video cards, and in particular to the NVIDIA Compute Unified Device Architecture (CUDA). A number of optimization strategies that have been used to achieve optimal performance on a graphic processing units (GPU) are also discussed. The actual benefits of running on the GPU rather than the central processing unit depends on the extent and duration of the simulated event; for large, long-running simulations, the GPU can be 70-to-80-times faster, while for short-lived eruptions with a small extents the speed improvements obtained are 40-to-50 times.
TL;DR: In this article, a generalized box model approach is presented for geochemical monitoring of active crater lakes, as highly dynamic natural systems, taking into account all the internal and external chemical-physical factors that affect the crater lake system.
Abstract: In the past, variations in the chemical contents (SO42−, Cl−, cations) of crater lake water have not systematically demonstrated any relationships with eruptive activity. Intensive parameters (i.e., concentrations, temperature, pH, salinity) should be converted into extensive parameters (i.e., fluxes, changes with time of mass and solutes), taking into account all the internal and external chemical–physical factors that affect the crater lake system. This study presents a generalized box model approach that can be useful for geochemical monitoring of active crater lakes, as highly dynamic natural systems. The mass budget of a lake is based on observations of physical variations over a certain period of time: lake volume (level, surface area), lake water temperature, meteorological precipitation, air humidity, wind velocity, input of spring water, and overflow of the lake. This first approach leads to quantification of the input and output fluxes that contribute to the actual crater lake volume. Estimating the input flux of the "volcanic" fluid (Qf- kg/s) –– an unmeasurable subsurface parameter –– and tracing its variations with time is the major focus during crater lake monitoring. Through expanding the mass budget into an isotope and chemical budget of the lake, the box model helps to qualitatively characterize the fluids involved. The (calculated) Cl− content and dD ratio of the rising "volcanic" fluid defines its origin. With reference to continuous monitoring of crater lakes, the present study provides tips that allow better calculation of Qf in the future. At present, this study offers the most comprehensive and up-to-date literature review on active crater lakes.
TL;DR: Vulcamera as discussed by the authors is a stand-alone program for the determination of volcanic SO2 fluxes using ultraviolet cameras, which enables field image acquisition and all the required post-processing operations.
Abstract: We report here on Vulcamera, a stand-alone program for the determination of volcanic SO2 fluxes using ultraviolet cameras. The code enables field image acquisition and all the required post-processing operations.
TL;DR: Galanopoulos as mentioned in this paper derived a linear relation of the earthquake intensity to the acceleratimi at the epicenter from the empiri cai equation: ara ǫ R = GE, which was proved to be appropriate for M-determination from macroseismic data.
Abstract: In the first paper (Galanopoulos, 1961), it was assumed that there is a linear relation of the earthquake intensity to the acceleratimi at the epicenter. On this assumption the magnitude formula: M = Oi log I0r + C2 [1] was derived from the empiri cai equation: ara„ R = GE [2] found by Gutenberg and Ricliter (1942). The formula [1] was proved to be appropriate for M-determination from macroseismic data. By using the basic relation: I = p log a + q [3] applied in ali macroseismic computations, the magnitude formula:
TL;DR: In this article, evidence was presented which supported the theory that the earthquake activity in the area of Greece should be attributed to horizontal currents flowing off to the side of the secondary sedimentary arc, from a minor mantle current rising under the primary volcanic arc of the Southeastern section of the Dinaric Alps.
Abstract: Evidence is presented which favours the theory that the earthquake activity in the area of Greece should bo ascribed to horizontal currents flowing off to the side of the secondary sedimentary arc, from a minor mantle current rising under the primary volcanic arc of the Southeastern section of the Dinaric Alps.
TL;DR: In this article, the authors propose that the seismic crisis of 1999 marked the arrival of the magmatic fluids into the hydrothermal system, which caused the observed geochemical variations that started in 1999 and culminated in 2002.
Abstract: Long time-series of chemical and isotopic compositions of Vesuvius fumaroles were acquired in the framework of the volcanic surveillance in the 1998-2010 period. These allow the identification of processes that occur at shallow levels in the hydrothermal system, and variations that are induced by deep changes in volcanic activity. Partial condensation processes of fumarolic water under near-discharge conditions can explain the annual 18O and deuterium variabilities that are observed at Vesuvius fumaroles. Significant variations in the chemical compositions of fumaroles occurred over the 1999-2002 period, which accompanied the seismic crisis of autumn 1999, when Vesuvius was affected by the most energetic earthquakes of its last quiescence period. A continuous increase in the relative concentrations of CO2 and He and a general decrease in the CH4 concentrations are interpreted as the consequence of an increment in the relative amount of magmatic fluids in the hydrothermal system. Gas equilibria support this hypothesis, showing a PCO2 peak that culminated in 2002, increasing from values of ~40 bar in 1998 to ~55-60 bar in 2001-2002. We propose that the seismic crisis of 1999 marked the arrival of the magmatic fluids into the hydrothermal system, which caused the observed geochemical variations that started in 1999 and culminated in 2002.
TL;DR: In this paper, a triangular network covering the surface of the Earth was constructed based on the spherical Delaunay approach, and average-weighted vertical variations in the Earth surface were estimated.
Abstract: The Earth expansion problem has attracted great interest, and the present study demonstrates that the Earth has been expanding, at least over the recent several decades. Space-geodetic data recorded at stations distributed globally were used (including global positioning system data, very-long-baseline interferometry, satellite laser ranging stations, and stations for Doppler orbitography and radiopositioning integrated by satellite), which covered a period of more than 10 years in the International Terrestrial Reference Frame 2008. A triangular network covering the surface of the Earth was thus constructed based on the spherical Delaunay approach, and average-weighted vertical variations in the Earth surface were estimated. Calculations show that the Earth is expanding at present at a rate of 0.24 ± 0.04 mm/yr. Furthermore, based on the Earth Gravitational Model 2008 and the secular variation rates of the second-degree coefficients estimated by satellite laser ranging and Earth mean-pole data, the principal inertia moments of the Earth (A, B, C) and in particular their temporal variations, were determined: the simple mean value of the three principal inertia moments (i.e., [A+B+C]/3) is gradually increasing. This clearly demonstrates that the Earth has been expanding, at least over the recent decades, and the data show that the Earth is expanding at a rate ranging from 0.17 ± 0.02 mm/yr to 0.21 ± 0.02 mm/yr, which coincides with the space geodetic evidence. Hence, based on both space geodetic observations and gravimetric data, we conclude that the Earth has been expanding at a rate of about 0.2 mm/yr over recent decades.
TL;DR: In this article, the effects of the forces that act on the volcanic system are discussed, and the time variations of high-temperature fumaroles acquired by continuous monitoring are presented.
Abstract: Fumarole temperatures are the ultimate results of many processes that are encountered by deep fluids during their passage to the surface. Here, the time variations of high-temperature fumaroles acquired by continuous monitoring are presented, to show the effects of the forces that act on the system. Data acquired by continuous monitoring of fumaroles and the time relationships with the different parameters related to the activity of the volcanic system are discussed. From 1998 to 2010, the temperature and compositional changes of fumarolic gases were monitored at the same time as variations in the number of volcanoseismic events, which indicate frequent variations of energy release (heat and mass flow, and seismic strain release). Geochemical modeling applied to the volcanic system of Vulcano Island suggests that the overall expansion of magmatic gas through the fractured system is an almost iso-enthalpic process at depth, which shifts to an adiabatic process at shallow depth, where the rock permeability increases. Thus, the time variations of the fumarole temperatures reflect various physical variations of the system that can either occur at depth or close to the surface. The temperature monitoring performed in the fumarolic area of La Fossa Cone showed short-term effects related to rain events, and negligible effects related to other external agents (ambient temperature and atmospheric pressure variations). At the same time, the long-term monitoring highlighted some mean-term and long-term variations. These last are the main characters observed in the time-series, and they both appear to be related to endogenous forces that perturb the equilibrium of this complex geochemical system.
TL;DR: The largest dataset ever recorded during a normal fault seismic sequence was acquired during the 2009 seismic emergency triggered by the damaging earthquake in L'Aquila (Italy) This was possible through the coordination of different rapid-response seismic networks in Italy, France and Germany.
Abstract: The largest dataset ever recorded during a normal fault seismic sequence was acquired during the 2009 seismic emergency triggered by the damaging earthquake in L'Aquila (Italy) This was possible through the coordination of different rapid-response seismic networks in Italy, France and Germany A seismic network of more than 60 stations recorded up to 70,000 earthquakes Here, we describe the different open-data archives where it is possible to find this unique set of data for studies related to hazard, seismotectonics and earthquake physics Moreover, we briefly describe some immediate and direct applications of emergency seismic networks At the same time, we note the absence of communication platforms between the different European networks Rapid-response networks need to agree on common strategies for network operations Hopefully, over the next few years, the European Rapid-Response Seismic Network will became a reality
TL;DR: The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized by evident morphological scarps and normal and right-lateral type movements that directly affect roads and buildings as discussed by the authors.
Abstract: The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized by evident morphological scarps and normal and right-lateral type movements that directly affect roads and buildings. The TF has an important role in the instability that affects the south-eastern flank of Mt. Etna, and it represents part of the southern boundary of the unstable sector. Starting from 2005, the TF has been monitored using continuous wire extensometers and by carrying out periodic direct measurements across the northern and central sectors. From 2005 to September 2009, the measurements show that the TF has undergone continuous extension of about 2-3 mm/yr. During the October 2009 to January 2010 period, the creep rate of the TF reached up to 5.5 to 7.0 mm/yr, and this was accompanied by several shallow, low magnitude earthquakes that were felt by local people. This episode appears to be linked to the increase in the sliding velocity of the eastern flank that occurred during 2009.