Volcanic Tremors at ASO Volcano

Kubotera, Akira

doi:10.1016/b978-0-444-41141-9.50008-5

Cited by 66 publications

(36 citation statements)

References 5 publications

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“…Six events from the August eruption and five from the October eruption were studied. Kubotera [1974] studied particle motion of tremor recorded in the caldera at Aso volcano and concluded that the tremor waveform is composed of waves traveling in various directions, giving rise to a complicated particle motion. The vertical channel functioned very well, so a comparison can be made between signals recorded during the two eruptions.…”

Section: Description Of the Data Collectedmentioning

confidence: 99%

Observations of volcanic tremor at Mount St. Helens Volcano

Fehler¹

1983

J. Geophys. Res.

155

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Digital recordings of ground motion during tremor episodes accompanying eruptions at Mount St. Helens Volcano in the state of Washington on August 7 and October 16–18, 1980, are studied. The spectra of the vertical component waveforms contain at least two dominant peaks at 1.0 and 1.3 Hz for all events recorded during both eruptions that were studied. Spectra of horizontal ground motion show peaks at 0.9 and 1.1 Hz. The relative amplitude of the two peaks changes between tremor episodes and during single tremor episodes and shows no consistent relation to amplitude of ground motion. Spectra of long‐period earthquakes are very similar to those of tremor events, suggesting that tremor is composed of many long‐period earthquakes that occur over a period of time. The unique waveform of tremor events observed at Mount St. Helens must be due to a source effect, since the relative amplitude of the two dominant peaks changes during tremor episodes. The path effect on tremor waveforms is small since there are no peaks in the spectra of waveforms recorded during tectonic earthquakes occurring in the vicinity of Mount St. Helens. The consistency of the location of the spectral peaks for the wide range of tremor amplitudes means that there must be a physical length at the source that is constant, independent of the amplitude of motion at the source. Variations in amplitude of motion generated during tremor events must be due to variations in the force driving the tremor. Amplitudes of ground motion varies between 0.11 and 4.7 μm. Seismic moment rates during the two eruptions are calculated using the model of Aki et al. (1977) and found to vary between 6×1018 and 1×1020 dynes cm s−1, which are larger than values found by Aki et al. (1977), who studied amplitudes of shallow tremor events recorded during the October 1963 eruption of Kilauea volcano in Hawaii. Study of tremor amplitudes recorded at Corvallis, Oregon, leads to the conclusion that tremor accompanying the cataclysmic May 18, 1980, eruption was at least one order of magnitude larger in amplitude than tremor during August and October.

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Section: Description Of the Data Collectedmentioning

confidence: 99%

Observations of volcanic tremor at Mount St. Helens Volcano

Fehler¹

1983

J. Geophys. Res.

155

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“…For example Sassa (1936) and later Shima (1958) and Kubotera (1974) suggested that the observed 10-s-period tremor at Mt. Aso was caused by the oscillation of a spherical magma chamber beneath the volcano.…”

Section: Resonance Of Large Magma Bodiesmentioning

confidence: 99%

Nature, wavefield properties and source mechanism of volcanic tremor: a review

Konstantinou

Schlindwein

2003

Journal of Volcanology and Geothermal Research

182

129

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Volcanic tremor has attracted considerable attention by seismologists because of its potential value as a tool for forecasting eruptions and better understanding the physical processes that occur inside active volcanoes. However, unlike tectonic earthquakes where the dominant source process is brittle failure of rock, the driving mechanism of tremor seems to involve complex interactions of magmatic fluids with the surrounding bedrock. These interactions are responsible for the following distinct characteristics found in volcanic tremor recorded at many volcanoes worldwide: (a) the onset of tremor may be emergent or impulsive, with its amplitude showing in many cases a direct relationship to the volcanic activity; (b) in the frequency domain the spectra consist of a series of sharp peaks in the band 0.1^7 Hz, representing either a fundamental frequency and its harmonics, or a random distribution, while quite often they exhibit temporal variations in their content; (c) the depth of the source can vary considerably from one volcano to another in the range of a few hundred metres to 40 km; (d) tremor may occur prior to and/or after eruptions with a duration that ranges from several minutes to several days or months. The methods used to study tremor include spectral analysis using both the Fast Fourier Transform and the Maximum Entropy Method, polarisation analysis of the wavefield and methods that make use of array data to deduce the backazimuth and type of the seismic waves as well as the location of the source. Visual and/or recorded acoustic observations of the ongoing volcanic activity have assisted in many cases to further constrain proposed physical mechanisms for the generation of tremor. The models suggested as possible sources of tremor can be grouped as follows: (a) fluid-flow-induced oscillations of conduits transporting magmatic fluids; (b) excitation and resonance of fluid-filled cracks; (c) bubble growth or collapse due to hydrothermal boiling of groundwater; (d) a variety of models involving the oscillations of magma bodies with different geometries. It has been proposed by many authors that the source of tremor is not unique and may differ from one volcano to another, a fact that adds more difficulty in the source modelling efforts. As data quality, computer power and speed are improving, it may be possible in the near future to decipher and accurately model tremor source processes at different volcanic environments. ß 2002 Elsevier Science B.V. All rights reserved.

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“…Some of them consist of free oscillations of a magma chamber (Kubotera 1974;Sassa 1935;Shima 1958); oscillations of gas in a volcanic vent (Steinberg and Steinberg 1975); oscillations of volcanic layers from moving magma (Omer 1950); random opening of tensile cracks due to an excess of fluid pressures (Aki et al 1977;Aki and Koyanagi 1981;Chouet 1981) and unstable flow in a magmatic fluid, due to the interaction between gas and fluid phases (Seidl et al 1981). Schick (1981) proposed multiple origins for volcanic tremor: mechanical instability of solid parts of the volcano, non-stationary magma fluid flow, vibrations induced by gases and/or water or interactions between solid, fluid and gas.…”

Section: Volcanic Tremormentioning

confidence: 99%

Alert system to mitigate tephra fallout hazards at Mt. Etna Volcano, Italy

et al. 2007

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Volcanic eruptions may create a wide range of risks in inhabited areas and, as a consequence, major economic damage to the surrounding territory. An example of volcanic hazard was given between 1998 and 2001 by Mt. Etna volcano, in Italy, with its frequent paroxysmal explosive activity that caused more than a hundred fire-fountain episodes. In the period January-June 2000, in particular, 64 lava fountains took place at the Southeast Crater. During the most intense explosive phase of each episode, a sustained column often formed, reaching up to 6 km above the eruptive vent. Then, the column started to expand laterally causing more or less copious tephra fallout on the slopes of Etna; ash and lapilli, therefore, constituted a serious danger for vehicular and air traffic. A software and hardware warning system was developed to mitigate the volcanic hazard indicating the areas affected by potential ash and lapilli fallout. The alert system was mainly based on the good correspondence between the pattern of volcanic tremor amplitude and the evolution of explosive activity. When a fixed tremor threshold was exceeded, a semiautomatic process started to send faxes to Civil Defence and Municipalities directly affected by tephra fallout, together with information on wind directions from the Meteorological Office. The application of this methodology, during the last 14 eruptive episodes in 2000 and the 14 events occurred in 2001, demonstrated the good correspondence between the forecasts on the areas affected by tephra fallout and the effective tephra distribution on land. Despite the integrity of the performance provided by the alert system, small discrepancies occurred in the technical procedure of alerting, for which possible solutions have been discussed. The improvement of this type of system, could become basic for the Etnean region and be proposed for similar volcanic areas throughout the world.

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Volcanic Tremors at ASO Volcano

Cited by 66 publications

References 5 publications

Observations of volcanic tremor at Mount St. Helens Volcano

Observations of volcanic tremor at Mount St. Helens Volcano

Nature, wavefield properties and source mechanism of volcanic tremor: a review

Alert system to mitigate tephra fallout hazards at Mt. Etna Volcano, Italy

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