1,721,133 research outputs found
Is there a correlation between larger local earthquakes and the end of eruptions at Mount Etna volcano, Sicily?
No full textThe correlation between destructive shallow local earthquakes (Io≧IX) and the largest eruptions (volume ≧ 107 m3), has been tested at Mount Etna volcano for the period 1600 to the present. These seismic events are found to be linked at a statistically significant level lower than 0.01 to the end of eruptions confirming previous results by Nercessian, Hirn & Sapin (1991). Copyright © 1994, Wiley Blackwell. All rights reserve
Current stress and strain-rate fields across the Dead Sea Fault System: Constraints from seismological data and GPS observations
Full text linkThe stress and strain-rate fields characterizing the Dead Sea Fault System are investigated by using seismological and geodetic observations. In order to assess spatial variations in the regional stress field, we compiled a multidisciplinary dataset of well-constrained horizontal indicators, by merging all available data reported in literature with the data obtained in this study through weighted stress inversions of focal plane solutions. Our findings indicate that the state of stress is characterized by the coexistence of a normal faulting stress regime with the primarily strike-slip one, according to the regional frame illustrated by previous geological and seismological observations. An updated velocity field computed from new observations and earlier published data depicts the general left-lateral motion of the Dead Sea Fault System well. In agreement with previous studies, we detected some differences in the slip-rate pattern between the northern and the southern sectors of the fault system. The geodetic strain-rate field highlights how much of the deformation is accommodated along the fault system itself in a narrow region. The comparison between the stress and the strain-rate directions reveals that both orientations are near-parallel, clearly indicating that present-day crustal stress and ground deformation patterns are chiefly driven by the same tectonic processes. (C) 2013 Elsevier B.V. All rights reserved
Time variation of spectral and wavefield features of volcanic tremor at Mt. Etna (January-June 1999)
No full textStatistical analysis of seismic and eruptive activities at Mt. Etna during 1978-1987
No full textSeismic and eruptive activities that occurred at Etna volcano during the decade 1978-1987 have been analyzed statistically. The seismic activity consists of about 7500 events. This catalog has been found complete above the magnitude threshold 2.8. On the basis of the complete catalog (1458 earthquakes), the clustering features of seismicity have been investigated. The hypothesis of a Simple Poisson process is rejected. Applying a Generalized Poisson process of the Shlien and Toksoz (1970) type, the "E" parameter of cluster size appears to be strongly dependent on the chosen time interval. The application of Gasperini and Mulargia (1989) algorithm for identifying the single earthquake sequences indicates that the whole period is composed of only three sequences. Etnean seismicity appears therefore characterized by a "diffuse" low-magnitude (less than about 3.0) earthquake occurrence. From the volcanological point of view, two time series of eruptions (flank and flank + summit) have been analyzed in order to identify different regimes in both magma output and inter-event time. No change-points are apparent in the magma output series, while both inter-event time series of flank and flank + summit eruptions are characterized by one change-point each. No evident relation between the series of eruptions and the identified earthquake sequences is apparent. © 1990
Analysis of the intermittent volcanic tremor observed at Mt. Etna, Sicily during March-May 1987
No full textVolcanic activity at the summit craters of Mt. Etna includes phreatic eruptions which jeopardize tourists and other people who sporadically approach the top of the volcano. To date no appreciable precursors of this kind of activity are known. Solely intermittent volcanic tremor might be considered a short-term seismic forerunner. The pattern of volcanic tremor amplitude at Mt. Etna during springtime 1987 was investigated and revealed significant periodicities before both phreatic explosions occurring at the summit craters during that time span. Results are in agreement with a boiling mechanism as the source of intermittent volcanic tremor, even if the lack of data on the ground water table in the upper part of the volcano did not allow the formulation of quantitative models
Magma intrusion mechanisms and redistribution of seismogenic stress at Mt. Etna volcano (1997-1998)
No full textSeveral volcanoes worldwide have shown changes in their stress state as a consequence of the deformation produced by the pressurization of a magmatic body. This study investigated seismic swarms occurring on the western flank of Mt. Etna in January 1997-January 1998. Integrating seismic observations and geodetic data, we constrained the seismogenic fault system, and on the basis of stress tensor inversion and SH(MAX) analyses, we inferred an inflating pressure source located at 5.5 km b.s.l. beneath the west portion of summit area. Evaluation of Coulomb failure stress related to the proposed model showed how a large part of the seismogenic fault underwent a significant Coulomb failure stress increase (500 kPa). We inferred the presence of a sub-vertical faulted region, potentially weak, N50 degrees E-oriented beneath the western sector of Mt. Etna. This structure could be brought closer to failure, thereby generating seismic swarms as the effect of elastic stress transfer induced by movement and/or overpressure of magmatic masses within the upper crust under the volcano
How a complex basaltic volcanic system works: Constraints from integrating seismic, geodetic, and petrological data at Mount Etna volcano during the July-August 2014 eruption
Full text linkIntegrating geodetic, seismic, and petrological data for a recent eruptive episode at Mount Etna has enabled us to define the history of magma storage and transfer within the multilevel structure of the volcano, providing spatial and temporal constraints for magma movements before the eruption. Geodetic data related to the July-August 2014 activity provide evidence of a magma reservoir at similar to 4kmbelow sea level. This reservoir pressurized from late March 2014 and fed magmas that were then erupted from vents on the lower eastern flank of North-East Crater (NEC) and at New South-East Crater (NSEC) summit crater during the July eruptive activity. Magma drainage caused its depressurization since mid-July. Textural and microanalytical data obtained from plagioclase crystals indicate similar disequilibrium textures and compositions at the cores in lavas erupted at the base of NEC and NSEC, suggesting comparable deep histories of evolution and ascent. Conversely, the compositional differences observed at the crystal rims have been associated to distinct degassing styles during storage in a shallow magma reservoir. Seismic data have constrained depth for a shallow part of the plumbing system at 1-2kmabove sea level. Timescales of magma storage and transfer have also been calculated through diffusion modeling of zoning in olivine crystals of the two systems. Our data reveal a common deep history of magmas from the two systems, which is consistent with a recharging phase by more mafic magma between late March and early June 2014. Later, the magma continued its crystallization under distinct chemical and physical conditions at shallower levels
An improved evaluation of the seismic/geodetic deformation-rate ratio for the Zagros Fold-and-Thrust collisional belt
No full textWe present an improved picture of the ongoing crustal deformation field for the Zagros Fold-and-Thrust Belt continental collision zone by using an extensive combination of both novel and published GPS observations. The main results define the significant amount of oblique Arabia-Eurasia convergence currently being absorbed within the Zagros: right-lateral shear along theNWtrending Main Recent fault inNWZagros and accommodated between fold-andthrust structures and NS right-lateral strike-slip faults on Southern Zagros. In addition, taking into account the 1909-2016 instrumental seismic catalogue, we provide a statistical evaluation of the seismic/geodetic deformation-rate ratio for the area. On Northern Zagros and on the Turkish-Iranian Plateau, a moderate to large fraction (~49 and >60 per cent, respectively) of the crustal deformation occurs seismically. On the Sanandaj-Sirjan zone, the seismic/geodetic deformation-rate ratio suggests that a small to moderate fraction (<40 per cent) of crustal deformation occurs seismically; locally, the occurrence of large historic earthquakes (M ≥ 6) coupled with the high geodetic deformation, could indicate overdue M ≥ 6 earthquakes. On Southern Zagros, aseismic strain dominates crustal deformation (the ratio ranges in the 15-33 per cent interval). Such aseismic deformation is probably related to the presence of the weak evaporitic Hormuz Formation which allows the occurrence of large aseismic motion on both subhorizontal faults and surfaces of décollement. These results, framed into the seismotectonic framework of the investigated region, confirm that the fold-and-thrust-dominated deformation is driven by buoyancy forces; by contrast, the shear-dominated deformation is primary driven by plate stresse
Magma transport and storage at Mt. Etna (Italy): a review of geodetic and petrological data for the 2002-03, 2004 and 2006 eruptions
Full text linkA detailed reconstruction of magma movements within the plumbing system of Mt. Etna volcano has been made by reviewing the eruptions occurring during the October 2002–December 2006 period. The availability of continuous GPS data allowed detecting at least ten different ground deformation stages, highlighting deflationary and inflationary episodes as well as the occurrence of a shallow dike intrusion. These data have been coupled with the available petrological datasets including major/trace elements and Sr-Nd-Pb isotope compositions for the volcanic rocks erupted in the 2002–2006 period. We identified two main magmatic reservoirs located at different depths along the plumbing system of the volcano. The former is located at a depth of ~ 7 km bsl and fed the 2001 and 2002–03 eruptions, while the latter, located from 3.5 to 5.5 km bsl, fed the 2004–05 and 2006 eruptions. Petrological characteristics of emitted products have been correlated with the inflation vs. deflation cycles related to the identified sources, providing evidence for changes through time of the evolutionary degree of the erupted magmas along with variations in their geochemical feature. Finally, we suggest that a modification of the deep plumbing system of the volcano might have occurred during the 2002–03 eruption, as a consequence of the major seaward motion of the eastern flank of the volcano
- …
