Geometric and kinematic variations along the active Pernicana fault: Implication for the dynamics of Mount Etna NE flank (Italy)

Geological and structural analyses and ground deformation measurements performed along the eastern portion of the Pernicana fault system and its splay segments allow the structural setting and the kinematic behaviour of the fault to be defined. In addition, the interrelationship between the deformation style of fault segments and the variations of the volcanic pile thickness along the fault strike are investigated using detailed sedimentary basement data. Brittle deformation dominates the N105 degrees fault segment, where the volcanic pile is more than 200 m thick, with the development of a well-defined fault plane characterised by main left-lateral kinematics. The transtensive deformation of the N105 degrees fault is partitioned eastward at Rocca Campana to a main N120 degrees segment. Here, this segment crosses a culmination of the sedimentary basement close to Vena village where the deformation pattern of the thin volcanic pile, less than 100 m thick, is influenced by the more ductile behaviour of the basement generating local short structures with different orientation and kinematics in the southern block of the fault. On the northern one, short E-W trending faults show left-lateral displacements with a minor reverse component on south-dipping planes. This kinematics is related to the oblique orientation of the N120 degrees segment with respect to the seaward motion of the NE flank of Etna. On the whole, the compressive component of the deformation affecting the N120 degrees segment of the Pernicana fault system generates a positive flower structure. (c) 2006 Elsevier B.V All rights reserved

Remote Sensing and Geodetic Measurements for Volcanic Slope Monitoring: Surface Variations Measured at Northern Flank of La Fossa Cone (Vulcano Island, Italy)

Abstract: Results of recent monitoring activities on potentially unstable areas of the NW volcano flank of La Fossa cone (Vulcano Island, Italy) are shown here. They are obtained by integration of data by aerial photogrammetry, terrestrial laser scanning (TLS) and GPS taken in the 1996–2011 time span. A comparison between multi-temporal models built from remote sensing data (photogrammetry and TLS) highlights areas characterized by ~7–10 cm/y positive differences (i.e., elevation increase) in the upper crown of the slope. The GPS measurements confirm these results. Areas characterized by negative differences, related to both mass collapses or small surface lowering, also exist. The higher differences, positive and negative, are always observed in zones affected by higher fumarolic activity. In the 2010–2012 time span, ground motions in the northern part of the crater rim, immediately above the upper part of observed area, are also observed. The results show different trends for both vertical and horizontal displacements of points distributed along the rim, with a magnitude of some centimeters, thus revealing a complex kinematics. A slope stability analysis shows that the safety factors estimated from these data do not OPEN ACCESS Remote Sens. 2013, 5 2239 indicate evidence of possible imminent failures. Nevertheless, new time series are needed to detect possible changes with the time of the stability conditions, and the monitoring has to go on

Seismic potential in the Italian Peninsula from integration and comparison of seismic and geodetic strain rates.

Seismological and geodetic data provide key information about the kinematics and active tectonics of plate margins. Focal solutions enable determining the directions in which the current tectonic stress acts when fault rupturing occurs; GPS measurements provide information on the crustal velocity field and on current interseismic strain rates. The comparison of the strain rates resulting from the two datasets provides further insight into how large an area is affected by aseismic deformation, which is a valuable indicator for seismic hazard mitigation and estimating the seismic potential. In this work, we investigate both seismic and geodetic strain rates and the combined field resulting from the joint inversion of the geodetic and seismic datasets, providing a picture of the overall deformation field and its variation during the last decades. In this way, we seek to give an overview of the seismic potential distribution across the Apennines and southern Italy, as a qualitative analysis of space-time variations in the released seismic strain rate, compared to the space-time distribution of the cumulated geodetic strain rate. The results show a variable distribution of the seismic efficiency over the peninsula. The Southern Apennines shows the greatest seismic potential, highlighting a significantly lower seismicity in the last two decades over an area affected by the highest total strain rates. The Messina Straits and eastern Sicily have a significant seismic potential, together with the Calabrian arc (from the Tindari-Letojanni and central Aeolian islands to the Mt. Pollino area), as a result of seismic gaps with respect to the combined strain rates in the investigated period. This long gap highlights the longer recurrence periods for the strongest earthquakes on this area. The central-northern Apennines and off-shore northern Sicily, show a lower seismic potential than central-southern Apennines, probably due to the more recent seismicity affecting these areas

Rate of Convergence to Barenblatt Profiles for the Fast Diffusion Equation

We study the asymptotic behaviour of positive solutions of the Cauchy problem for the fast diffusion equation near the extinction time. We find a continuum of rates of convergence to a self-similar profile. These rates depend explicitly on the spatial decay rates of initial data

Ground deformations related to the effusive eruptions of Stromboli: the 2002-2003 case

Stromboli volcano erupted suddenly on 28 December 2002 after a long period of typically persistent and moderate explosive activity. Lava flows outpoured from the northern wall of the NE crater and descended into the Sciara del Fuoco (SdF). On December 30th, 2002, two landslides occurred on the northern part of the SdF, producing a tsunami that caused significant damage. This event led to the upgrading of the ground deformation monitoring system. The new requisite was the real-time detection of the deformation related both to the magma movements within the eruptive feeding system and to potential slope failures of the SdF. To this end, a remotely controlled monitoring system, based both on high-frequency (1 Hz) instantaneous GPS and terrestrial geodetic techniques (manual EDM measurements, transformed in automated terrestrial geodetic measurements) was planned and set up in a few months. During the recorded eruptive phases, the new monitoring system aided the Department of Civil Protection in making decisions related to hazards from landslides and volcanic activity and, more generally, on the evolution of volcanic phenomena throughout the eruption. The measurements carried out on the benchmarks located on the high flank allowed us to make some hypotheses on the dynamics of the craters. In particular, the behaviour of the EDM baselines, showing alternating periods of increase and periods of stop in length variation, could be linked to movements of the magmatic column within the craters. Moreover, the monitoring system gave us the opportunity to observe the effects of an effusive vent opening on February 16th. The new geodetic network provided, for the first time, useful information on ground deformations due to shallow and very shallow volcanic sources at Stromboli

Atmospheric anomalies over Mt.Etna using GPS signal delays and tomography of radio wave velocities

Due to the prominent topography of Mt. Etna, the use of satellite geodetic techniques may significantly suffer from atmospheric heterogeneities. This problem mainly affects the DInSAR technique. To overcome these drawbacks the present study attempts to make headway in measuring and interpreting atmospheric anomalies. We used the GAMIT software to obtain the ZTD (Zenith Total Delay) values for the GPS sessions performed on 1996-97, during ERS-2 passes at Mt. Etna. GAMIT software also allows to characterize the statistical behaviour of the tropospheric effects, by using residuals for each station-satellite pair, and to locate the atmospheric anomalies, present mostly at low altitudes. The attempt at using these results to produce a tomography of radio waves velocity of the troposphere suggests that the number of GPS stations used to investigate atmosphere is a critical point in such a study. The three stations are too few to invert anomalies eventually existing in the lower atmosphere. This result is a good starting point for better direct future study to verify the applicability of this tomographic technique to a geodetic network with a higher number of stations, with the aim of characterizing the lower atmosphere of Mt. Etna for a more accurate monitoring of ground deformations

Ground deformation modeling of flank dynamics prior to the 2002 eruption of Mt. Etna

On 22 September 2002, 1 month before the beginning of the flank eruption on the NE Rift, an M-3.7 earthquake struck the northeastern part of Mt. Etna, on the westernmost part of the Pernicana fault. In order to investigate the ground deformation pattern associated with this event, a multi-disciplinary approach is presented here. Just after the earthquake, specific GPS surveys were carried out on two small sub-networks, aimed at monitoring the eastern part of the Pernicana fault, and some baselines belonging to the northeastern EDM monitoring network of Mt. Etna were measured. The leveling route on the northeastern flank of the volcano was also surveyed. Furthermore, an investigation using SAR interferometry was performed and also the continuous tilt data recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation. The results of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano, clearly shaped by the Pernicana fault, but too strong and wide to be related only to an M-3.7 earthquake. Leveling and DInSAR data highlight a local strong subsidence, up to 7 cm, close to the Pernicana fault. Significant displacements, up to 2 cm, were also detected on the upper part of the NE Rift and in the summit craters area, while the displacements decrease at lower altitude, suggesting that the dislocation did not continue further eastward. Three-dimensional GPS data inversions have been attempted in order to model the ground deformation source and its relationship with the volcano plumbing system. The model has also been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by SAR interferometry

Ground deformation modeling of flank dynamics prior to the 2002 eruption of Mt. Etna

On 22 September 2002, 1 month before the beginning of the flank eruption on the NE Rift, an M-3.7 earthquake struck the northeastern part of Mt. Etna, on the westernmost part of the Pernicana fault. In order to investigate the ground deformation pattern associated with this event, a multi-disciplinary approach is presented here. Just after the earthquake, specific GPS surveys were carried out on two small sub-networks, aimed at monitoring the eastern part of the Pernicana fault, and some baselines belonging to the northeastern EDM monitoring network of Mt. Etna were measured. The leveling route on the northeastern flank of the volcano was also surveyed. Furthermore, an investigation using SAR interferometry was performed and also the continuous tilt data recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation. The results of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano, clearly shaped by the Pernicana fault, but too strong and wide to be related only to an M-3.7 earthquake. Leveling and DInSAR data highlight a local strong subsidence, up to 7 cm, close to the Pernicana fault. Significant displacements, up to 2 cm, were also detected on the upper part of the NE Rift and in the summit craters area, while the displacements decrease at lower altitude, suggesting that the dislocation did not continue further eastward. Three-dimensional GPS data inversions have been attempted in order to model the ground deformation source and its relationship with the volcano plumbing system. The model has also been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by SAR interferometry

Magma storage, eruptive activity and flank instability: inferences from ground deformation and gravity changes during the 1993-2000 recharging of Mt. Etna volcano

A long recharging period characterized Mount Etna volcano during 1993-2000 before the main explosive-effusive 2001 and 2002-03 flank eruptions. The joint analysis of ground deformation and gravity data over this entire period revealed that different phenomena occurred within Etna's plumbing system and clearly inferred two phases spanning 1993-97 and 1994-2000, respectively. The first phase was characterized by magma storage and accumulation at an intermediate depth (2-6 km below sea level), which provoked an overall inflation and positive gravity changes. During the second phase, the magma started to rise and intrude at shallower levels favouring the movement of the unstable eastern flank, which accelerated its sliding toward the East. The shallower magma accumulation also caused the gas exolution, associated with increasing explosive activity at the summit craters, detected by a gravity negative variation. The gravity measurements, independently of the same result obtained by geochemical studies, confirm that only 20-30% of the magma volumes supplied in the plumbing system were then erupted. The complex dynamic of rising magma beneath Mount Etna makes ground deformation and gravity measurements complementary, being able to detect different effects of magma emplacements beneath the surface. Our results also highlight how the joint use of ground deformation and gravity observations may be crucial in identifying the nature and rate of an impending season of volcanic eruptions

On the asymptotic behaviour of solutions to the fractional porous medium equation with variable density

We are concerned with the long time behaviour of solutions to the fractional porous medium equation with a variable spatial density. We prove that if the density decays slowly at infinity, then the solution approaches the Barenblatt-type solution of a proper singular fractional problem. If, on the contrary, the density decays rapidly at infinity, we show that the minimal solution multiplied by a suitable power of the time variable converges to the minimal solution of a certain fractional sublinear elliptic equation.Comment: To appear in DCDS-