TY - JOUR

T1 - Volcanic tremor during eruptions

T2 - Temporal characteristics, scaling and constraints on conduit size and processes

AU - McNutt, Stephen R.

AU - Nishimura, Takeshi

N1 - Funding Information:
We are grateful to H. Hamaguchi for providing us the unpublished data of Volcano Nyiragongo and to K. Uhira for giving us information on tremor data of Mt. Miyake. An earlier draft of the paper was reviewed by J. Benoit, M. Garces, H. Shimozuru and B. Sturtevant. Matthias Hort and Silvio de Angelis kindly provided comments on the current draft. This study was partly supported by the foreign scientist invitation program of the Japan Society for Promoting Science, by the U.S. National Science Foundation under grant EAR-9418219, by the 21COE Program of Tohoku University, and by the U.S. Geological Survey as part of the Volcano Hazards Program, and by additional funds from the State of Alaska to the Alaska Volcano Observatory.

PY - 2008/11/30

Y1 - 2008/11/30

N2 - We investigated characteristics of eruption tremor observed for 24 eruptions at 18 volcanoes based on published reports. In particular, we computed reduced displacements (DR) to normalize the data and examined tremor time histories. We observed: (a) maximum DR is approximately proportional to the square root of the cross sectional area of the vent, however, with lower than expected slope; (b) about one half of the cases show approximately exponential increases in DR at the beginnings of eruptions, on a scale of minutes to hours; (c) one half of the cases show a sustained maximum level of tremor; (d) more than 90% of the cases show approximately exponential decay at the ends of eruptions, also on a scale of minutes to hours; and (e) exponential increases, if they occur, are commonly associated with the first large stage of eruptions. We estimate the radii of the vents using several methods and reconcile the topographic estimates, which are systematically too large, with those obtained from DR itself and theoretical considerations. We compare scaling of tremor DR with that for explosions and find that explosions have large absolute pressures and scale with vent radius squared, whereas tremor consists of pressure fluctuations that have lower amplitudes than the absolute pressure of explosions, and the scaling is different. We explore several methods to determine the appropriate scaling. This characteristic helps us to distinguish the type of eruptions: explosive (Vulcanian or Strombolian) eruptions versus sustained or continuous ash (e.g. Plinian) eruptions. Average eruption discharge, estimated from the total volume of tephra and the total duration of eruption tremor, is well correlated with peak discharge calculated from cross sectional area of the vent and velocity of volcanic ejecta. These results suggest similar scaling between different eruption types and the overall usefulness of monitoring tremor for evaluating volcanic activity.

AB - We investigated characteristics of eruption tremor observed for 24 eruptions at 18 volcanoes based on published reports. In particular, we computed reduced displacements (DR) to normalize the data and examined tremor time histories. We observed: (a) maximum DR is approximately proportional to the square root of the cross sectional area of the vent, however, with lower than expected slope; (b) about one half of the cases show approximately exponential increases in DR at the beginnings of eruptions, on a scale of minutes to hours; (c) one half of the cases show a sustained maximum level of tremor; (d) more than 90% of the cases show approximately exponential decay at the ends of eruptions, also on a scale of minutes to hours; and (e) exponential increases, if they occur, are commonly associated with the first large stage of eruptions. We estimate the radii of the vents using several methods and reconcile the topographic estimates, which are systematically too large, with those obtained from DR itself and theoretical considerations. We compare scaling of tremor DR with that for explosions and find that explosions have large absolute pressures and scale with vent radius squared, whereas tremor consists of pressure fluctuations that have lower amplitudes than the absolute pressure of explosions, and the scaling is different. We explore several methods to determine the appropriate scaling. This characteristic helps us to distinguish the type of eruptions: explosive (Vulcanian or Strombolian) eruptions versus sustained or continuous ash (e.g. Plinian) eruptions. Average eruption discharge, estimated from the total volume of tephra and the total duration of eruption tremor, is well correlated with peak discharge calculated from cross sectional area of the vent and velocity of volcanic ejecta. These results suggest similar scaling between different eruption types and the overall usefulness of monitoring tremor for evaluating volcanic activity.

KW - conduit radius

KW - eruptions

KW - explosions

KW - scaling

KW - volcanic tremor

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U2 - 10.1016/j.jvolgeores.2008.03.010

DO - 10.1016/j.jvolgeores.2008.03.010

M3 - Article

AN - SCOPUS:55749106077

SN - 0377-0273

VL - 178

SP - 10

EP - 18

JO - Journal of Volcanology and Geothermal Research

JF - Journal of Volcanology and Geothermal Research

IS - 1

ER -