1,721,222 research outputs found
The Tectonics and Physics of Volcanoes. Journal of Volcanology and Geothermal Research, 144
No full textThe tectonics and physics of volcanoes. Structural control of volcanism and caldera development in the transtensional Taupo Volcanic Zone, New Zealand. Structural setting of the Bicol Basin and kinematic analysis of fractures on Mayon Volcano, Philippines. The Managua Graben and Las Sierras-Masaya volcanic complex (Nicaragua); pull-apart localization by an intrusive complex: results from analogue modeling. On trapdoor faulting at Sierra Negra volcano, Galapagos. Graben structure in the Las Cañadas edifice (Tenerife, Canary Islands): implications for active degassing and insights on the caldera formation. Effects of changing stress states on the development of caldera-bounding faults: Geological evidence from Kumano caldera, Japan. Structural and rheological constraints on source depth and overpressure estimates at the Campi Flegrei caldera, Italy. Elliptical calderas in active tectonic settings: an experimental approach. Nested zones of instability in the Mount Etna volcanic edifice, Italy. The 1980 pressure response and flank failure of Mount St. Helens (USA) inferred from seismic scaling exponents. Landslides and spreading of oceanic hot-spot and arc shield volcanoes on Low Strength Layers (LS Stability of a collapsing volcano (Stromboli, Italy): Limit equilibrium analysis and numerical modelling Ls): an analogue modeling approach. Tectonic control on the eruptive dynamics at Mt. Etna Volcano (Sicily) during the 2001 and 2002-2003 eruptions. Contrasting triggering mechanisms of the 2001 and 2002-2003 eruptions of Mount Etna (It Finite element modelling of topographic effects on elastic ground deformation at Mt. Etna aly). Buoyancy-driven fracture ascent: Experiments in layered gelatine. Four-dimensional upper crustal construction at fast-spreading mid-ocean ridges: A perspective from an upper crustal cross-section at the Hess Deep Rift. Dyke emplacement in a layered and faulted rift zone
Volcanic systems. Geochemical and geophysical monitoring. Melt inclusions: Methods and Applications
No full textComment on ‘Are the source models of the M 7.1 1908 Messina Straits earthquake reliable? Insights from a novel inversion and sensitivity analysis of levelling data’ by M. Aloisi, V. Bruno, F. Cannav ` o, L. Ferranti, M. Mattia, C. Monaco and M. Palano
No full textIn a recent paper, important issues were raised about the identification of the fault responsible
for the 1908 Messina Straits earthquake. Starting with a reanalysis of the available original
geodetic data, the authors aimed to demonstrate that both of the fault–plane orientations
derived by the focal mechanism are compatible with the measurements. On these grounds, and
based on geological considerations, they argued in favour of the Armo fault—a high-angled
structure on the Calabrian side of the Messina Straits—as responsible for the 1908 earthquake.
We indicate here that their analysis has some pitfalls that produce questionable results, and that
render their conclusions unreliable. Moreover, especially when dealing with such old events
and data, we consider that it is more prudent not to derive conclusions on the basis of a single
data set, as all of the available information should be included in any interpretation. Indeed,
when the joint results of the seismological and geodetic analyses are taken into account, a
consistent and robust source model can be derived that indicates that a low-angle, east-dipping
fault is the most likely source of this 1908 Messina Straits earthquakePublished1399-14024T. Fisica dei terremoti e scenari cosismiciJCR Journalrestricte
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Focal mechanism determination for voIcanic microearthquakes
No full textClassical methods to infer focal mechanisms from first P wave motions are of limited use for the analysis of small magnitude events occurring in volcanic areas, due to structure complexity. This work presents an alternative way to compute focal mechanisms of earthquakes in volcanic areas, based on a Bayesian approach. The probability density on the whole space spanned by source parameters is graphically represented, by a method originally due to Bernard and Zollo (1989). The data used to infer the probability density function can be of various kinds, like P wave polarities, S wave polarizations and S/P direct wave amplitude ratios. S wave polarizations are left practically unchanged by smooth variations of velocity, and are only sensitive to strong discontinuities and/or seismic anisotropy. S/P amplitude ratios of direct waves are also good observables, not very sensitive to frequency independent amplification effects. They are still affected by differential S-P anelastic attenuation, although to a much lesser extent than absolute S and P amplitudes. In fact, the use of complete waveforms is not desiderable in volcanic areas because wave amplitudes may be strongly biased by not well known path and site effects, mainly for non direct waves which are most affected by medium heterogeneities. Such unmodeled elastic and anelastic features of the medium can be traded off for source characteristics, leading to bad results. The use of the probabilistic approach, and the seloction of robust observables, allow us to solve many problems of classical methods. The determination of the whole probability density on the parameter space visualizes all the information contained in the data set, checking completely the goodness of the solution, and its univoqueness. Furthermore, the use of different kinds of robust data sets helps to constrain the solution, and to minimize the influence of unmodeled medium heterogeneities. In the present method, it is possible to parameterize the source in terms of both double couple sources, and other kinds of sources generally hypothesized on volcanoes (tensile crack, CLVD, explosion) or generic sources characterized by five normalized independent components of the moment tensor. S/P amplitude ratios are shown to be those which most constrain the source mechanism. Furthermore, this paper analyzes the influence of anelastic attenuation on S and P absolute amplitudes, and on S/P amplitude ratios. An example of application to a small (ML = 2.0) earthquake which occurred at Campi Flegrei caldera is reported, showing how the different data sets constrain the solution. Finally, an example is reported of extensive application of the method to the analysis of small earthquakes which occurred at Campi Flegrei (Southern Italy) caldera during an unrest episode (1982-1984). It is shown how the accurate analysis of small earthquakes within a caldera has helped to solve important volcanological questions like: the caldera structure, the mechanism of earthquake generation during unrest episodes, and the features of ground deformations in calderas.JCR Journalope
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