Source and path effects in the wave fields of tremor and explosions at Stromboli Volcano, Italy

Abstract

Abstract. The wave fields generated by Strombolian activity are investigated using data from small-aperture seismic arrays deployed on the north flank of Stromboli and data from seismic and pressure transducers set up near the summit crater. Measurements of slowness and azimuth as a function of time clearly indicate that the sources of tremor and explosions are located beneath the summit crater at depths shallower than 200 rn with occasional bursts of energy originating from sources extending to a depth of 3 km. Slowness, azimuth, and particle motion measurements reveal a complex composition of body and surface waves associated with topography, structure, and source properties. Body waves originating at depths shallower than 200 rn dominate the wave field at frequencies of 0.5-2.5 Hz, and surface waves generated by the surficial part of the source and by scattering sources distributed around the island dominate at frequencies above 2.5 Hz. The records of tremor and explosions are both dominated by SH motion. Far-field records from explosions start with radial motion, and near-field records from those events show dominantly horizontal motion and often start with a low-frequency (1-2 Hz) precursor characterized by elliptical particle motion, followed within a few seconds by a highfrequency radial phase (1-10 Hz) accompanying the eruption of pyroclastics. The dominant component of the near-and far-field particle motions from explosions, and the timing of air and body wave phases observed in the near field, are consistent with a gaspiston mechanism operating on a shallow (<200 rn deep), vertical crack-like conduit. Models of a degassing fluid column suggest that noise emissions originating in the collective oscillations of bubbles ascending in the magma conduit may provide an adequate self-excitation mechanism for sustained tremor generation at Stromboli.

Self-sustained oscillator as a model for explosion quakes at Stromboli Volcano

“…Here we evaluate d a first in a moving window of 3.5 s. This choice of window length is due to our capability to model only about 3. of the evaluation for d a , these values contain some information on the evolution of dynamics and on the stationarity of our signal. The choice of the window length is also determined from the results of Chouet et al (1997) who suggest that the source is limited to the first 10 s of the signal while the other part is affected by strong scattering. The analogue of Fig.…”

“…An accurate description of the deployed network and the instrumentation can be found in Chouet et al (1997). We are specifically interested in the following: the wavefield effectively comes from craters and it is composed of body waves in the first few seconds (see also Del Pezzo et al, 1992).…”

Radon mapping, automatic measurements and extremely high 222Rn emissions during the 2002–2007 eruptive scenarios at Stromboli volcano

“…Seismic data indicate that its source is confined within the magma column at relatively shallow depths (< 300 m) (Chouet et al, 1997). Moreover, seismic tremor and infrasonic puffing seem to have a common source likely related to in-conduit degassing Ripepe and Gordev, 1999).…”

Self-sustained vibrations in volcanic areas extracted by Independent Component Analysis: a review and new results

“…Sometimes, it is interrupted by effusive phases and/or by big explosive The seismic wavefield at Stromboli has been extensively studied by using advanced signal processing techniques. In particular, Del Pezzo et al (1992), Chouet et al (1997), and Acernese et al (2003Acernese et al ( , 2004 studied the composition of the high-frequency wavefield (> 0.5Hz) associated with the explosion quakes. Chouet et al (2003) investigated the seismic wavefield associated with very long period events (VLP), and retrieved the equivalent elastic source mechanism which includes both moment tensor and single force components.…”