Spatial mapping of the b value at Mount Etna, Italy, using earthquake data recorded from 1999 to 2005

Abstract

The spatial pattern of the b value of the frequency‐magnitude relation has been analyzed using gridding techniques beneath Mount Etna, Italy. A regional data set of 2900 events with Md (duration magnitude) ≥1.5 up to 15 km depth occurring between August 1999 and December 2005 has been used. Two regions with an abnormally high b value have been found, one centered beneath the southern part of the Valle del Bove, above the 6 km below sea level (bsl) deep basement, and the other beneath the summit region 2 km bsl east of the Central Craters. We can infer that these high b value anomalies are regions of increased crack density, and/or high pore pressure, related to the presence of nearby magma storage. This interpretation is supported by all the available geophysical evidence, such as tomographic studies and geodetic deformation measurements. The data set has also been subdivided into five periods, corresponding to different phases of volcanic activity: 2001 preeruption, 2001 eruptive, 2002–2003 preeruption, 2002–2003 eruptive, and 2002–2003 posteruption. The minimum magnitude of completeness, Mc, and the b value were computed for each period. A volume of anomalously high b values can be observed in each of these periods (except for the 2002–2003 preeruption interval). This approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated.

When probabilistic seismic hazard climbs volcanoes: the Mt. Etna case, Italy – Part 1: Model components for sources parameterization

“…This overall picture shows analogies with the pattern found by Murru et al (1999Murru et al ( , 2007 on a temporally different earthquake dataset (1999)(2000)(2001)(2002)(2003)(2004)(2005), highlighting two areas characterized by higher b values than other surrounding areas: (i) beneath the central craters and (ii) in the eastern flank, at a depth range of 5-7 km. Although the b values cannot be compared as absolute numbers because they were calculated from two different magnitude scales -M L in this study, M d in the Murru et al (2007) paper -the aforementioned spatial variations remain constant during time though the datasets cover contiguous time windows.…”

“…This overall picture shows analogies with the pattern found by Murru et al (1999Murru et al ( , 2007 on a temporally different earthquake dataset (1999)(2000)(2001)(2002)(2003)(2004)(2005), highlighting two areas characterized by higher b values than other surrounding areas: (i) beneath the central craters and (ii) in the eastern flank, at a depth range of 5-7 km. Although the b values cannot be compared as absolute numbers because they were calculated from two different magnitude scales -M L in this study, M d in the Murru et al (2007) paper -the aforementioned spatial variations remain constant during time though the datasets cover contiguous time windows. The spatial distribution of the statistical parameters obtained from the IET analysis (Sicali et al, 2014) also displays similar lateral variations, indicating that the characteristics of earthquake occurrence in the central sector are very different from PF or SZ Timpe, the latter being more similar to the IET distribution observed in purely tectonic settings.…”

“…It is true that historical destructive earthquakes in the Timpe area did occur both during flank eruptions and during periods of volcanic quiescence; correlation studies of major seismic events and volcanic activity have not produced univocal results (Gasperini et al, 1990;Nercessian et al, 1991;Gresta et al, 1994). The inter-event time (IET) statistical analysis (Sicali et al, 2014) shows that the occurrence of low-magnitude (M < 3) shallow earthquakes in the central sector of the volcano, beneath the summit craters, depends mainly on the volcanic activity and produces a seismicity clustered in space and time.…”

The dyke swarm of Mount Calanna (Etna, Italy): an example of the uppermost portion of a volcanic plumbing system

“…Geophysics can provide information on the geometry of plumbing system, magma chamber/s, mechanisms of emplacement of dykes, etc. (e.g., Murru et al 1999;Iuliano et al 2002;De Gori et al 2005;Mattia et al 2008), but another way to understand the mechanism of emplacement of dykes swarm is to study subvolcanic bodies (i.e., magma chambers, dykes, and sills), which reside in the upper Editorial responsibility: R. Cioni Electronic supplementary material The online version of this article (doi:10.1007/s00445-010-0398-z) contains supplementary material, which is available to authorized users. crustal levels and commonly crop out in the deeply eroded roots of many volcanic edifices characterized by basic volcanism.…”

Medium condition variations beneath Klyuchevskaya volcano group assessment with seismic tomography and frequency-magnitude relation analysis

“…Стоит отметить, что проведен ряд успешных ис-следований вариаций этого параметра в других вулка-нических областях -например, исследования таких вулканов как Пинатубо [Sánchez et al, 2004], Галерас [Sánchez et al, 2005] Этны [Murru et. al., , 2007, вулканов Аляски [Wiemer, McNutt, 1997;Bridges, Gao, 2006], вулкано-тектонической системы Йеллоустоуна [Farrel et al, 2009] и др.…”