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Quantitative analysis of the tremor wavefield at Etna Volcano, Italy
Author(s)
Language
English
Status
Published
Peer review journal
Yes
Title of the book
Issue/vol(year)
136
Publisher
Elsevier
Pages (printed)
223-245
Issued date
2004
Alternative Location
Abstract
The properties of volcanic tremor wavefield at Mt. Etna Volcano, Italy, are investigated using data from two dense, smallaperture arrays of short-period seismometers deployed on the North and South flank of the volcano. Spectral analysis shows that most of the seismic energy is associated to several, narrow spectral peaks spanning the 1–5 Hz frequency band. Analysis of simultaneous recordings evidences that most of these peaks are common to different sites, thus suggesting a source effect as the origin of this energy. Frequency-slowness analyses evidence a complex wavefield, where body- and surface-waves alternatively dominate depending on the frequency band and component of motion taken into account. Surface waves are found to dominate at frequencies below 1 Hz and above 3 Hz. Conversely, the 0.8–2.3 Hz vertical- and radial-component wavefields at both arrays exhibit a nondispersive nature, with apparent velocities spanning the 1–2 s/km range. Particle motion analysis suggests these arrivals are associated to both P- and SV-waves inciding at shallow angles. At the northern array, back-azimuths of these waves encompass the whole summit crater area. At the southern array, back-azimuths are instead clustered around a direction pointing about 500 m east of the SE crater. At frequency around 4 Hz, the dominant
direction of wave propagation at the southern site shifts about 30jW, pointing to the Bocca-Nuova/Voragine craters, and
concordance of location is found with the source imaged by the northern array. The 0.8–2.3 Hz transverse-component of motion depicts velocities of about 0.5 km/s, a value which is about three times lower than those associated to the vertical and
radial components. Results from polarization analyses at the two array sites depict the dominance of horizontal, linear particle motion oriented transversally with respect to the source direction. Polarization ellipsoids at the stations of the sparse network all depict a quasi-horizontal setting. With two exceptions, the direction of particle motion is always oriented tangentially to
the summit volcanic edifice. The origin of the large transverse motion observed at the two array sites is thus attributed to SH
waves generated by free-surface interaction of waves impinging the concave topography. The correlation method is used to derive the dispersion properties of short-period (0.5–5 Hz) Rayleigh waves, from which the shallow shear-wave velocity structures are derived for beneath the two semicircular arrays. Using a probabilistic approach, we invert slowness data measured at the two dense arrays for retrieving source location and extent. The joint inversion of slowness data from the two arrays point to different sources. This observation is interpreted in terms of ray bending associated to lateral heterogeneity and/or strong topographic effects on wave propagation. Once the propagation effects are taken into account, the most probable source locations are associated to a shallow region encompassing the summit craters and the eruptive fissures active at the time of the experiment (September 1999).
direction of wave propagation at the southern site shifts about 30jW, pointing to the Bocca-Nuova/Voragine craters, and
concordance of location is found with the source imaged by the northern array. The 0.8–2.3 Hz transverse-component of motion depicts velocities of about 0.5 km/s, a value which is about three times lower than those associated to the vertical and
radial components. Results from polarization analyses at the two array sites depict the dominance of horizontal, linear particle motion oriented transversally with respect to the source direction. Polarization ellipsoids at the stations of the sparse network all depict a quasi-horizontal setting. With two exceptions, the direction of particle motion is always oriented tangentially to
the summit volcanic edifice. The origin of the large transverse motion observed at the two array sites is thus attributed to SH
waves generated by free-surface interaction of waves impinging the concave topography. The correlation method is used to derive the dispersion properties of short-period (0.5–5 Hz) Rayleigh waves, from which the shallow shear-wave velocity structures are derived for beneath the two semicircular arrays. Using a probabilistic approach, we invert slowness data measured at the two dense arrays for retrieving source location and extent. The joint inversion of slowness data from the two arrays point to different sources. This observation is interpreted in terms of ray bending associated to lateral heterogeneity and/or strong topographic effects on wave propagation. Once the propagation effects are taken into account, the most probable source locations are associated to a shallow region encompassing the summit craters and the eruptive fissures active at the time of the experiment (September 1999).
References
Allard, P., 1997. Endogenous magma degassing and storage at Mount Etna. Geophys. Res. Lett. 24, 2219–2222.
Almendros, J., Chouet, B.A., Dawson, P.B., 2001a. Spatial extent of a hydrothermal system at Kilauea Volcano, Hawaii, determined from array analyses of shallow long-period seismicity: 1. Method. J. Geophys. Res. 106, 13565– 13580.
Almendros, J., Chouet, B.A., Dawson, P.B., 2001b. Spatial extent of a hydrothermal system at Kilauea Volcano, Hawaii, determined from array analyses of shallow long-period seismicity: 2. Results. J. Geophys. Res. 106, 13581–13597.
Almendros, J., et al., 2002. Mapping the sources of the seismic wavefield at Kilauea Volcano, Hawaii, using data recorded on multiple seismic antenna. Bull. Seismol. Soc. Am. 92, 2333–2351.
Aki, K., 1957. Space and time spectra of stationary stochastic waves, with special reference to microtremors. Bull. Earthq.
Res. Inst. Univ. Tokyo 25, 415–457.
Aki, K., 1959. Correlation study of near earthquake waves. Bull. Earthq. Res. Inst. Univ. Tokyo 37, 207– 232.
Aki, K., Chouet, B., Fehler, M., Zandt, G., Koyanagi, R., Colp, J., Hay, R.G., 1978. Seismic properties of a shallow magma reservoir in Kilauea Iki by active and passive experiments. J. Geophys. Res. 83, 2273–2282.
Benoit, J., McNutt, S.R., 1997. New constraints on the source processes of volcanic tremor at Arenal volcano, Costa Rica, using broadband seismic data. Geophys. Res. Lett. 24, 449– 452.
Calvari, S., Neri, M., Pinkerton, H., 2002. Effusion rate estimations during the 1999 summit eruption on Mount Etna, and growth of two distinct lava flow fields. J. Volcanol.Geotherm. Res. 119, 107– 123.
Castellano, M., Capello, M., Del Pezzo, E., Giudicepietro, F., La Rocca, M., Martini, M., Petrosino, S., Saccorotti, G., Ibanez, J., Abril, M., Almendros, J., Carmona, E., Martinez, C., Vilchez, J., Privitera, E., Alparone, S., Di Grazia, G., Gresta, S., 2000. A double seismic array experiment on Mt. Etna. Osservatorio Vesuviano Open file report n. 2-2000, 30 pp. (available on line at Http://www.ov.ingv.it/italiano/pubblicazioni/openfile/ofr_02_00.htm).
Chiou, S.J., Bolt, B.A., 1993. Seismic wave slowness-vector estimation from broad-band array data. Geophys. J. Int. 114, 234– 248.
Chouet, B.A., 1988. Resonance of a fluid-driven crack: radiation properties and implications for the source of long-period events and harmonic tremor. J. Geophys. Res. 93, 4375– 4400.
Chouet, B.A., Saccorotti, G., Martini, M., Dawson, P.B., De Luca, G., Milana, G., Scarpa, R., 1997. Source and path effects in the wavefields of tremor and explosions at Stromboli volcano, Italy. J. Geophys. Res. 102, 15129– 15150.
Del Pezzo, E., De Martino, S., Gresta, S., Martini, M., Milana, G., Patane`, D., Sabbarese, C., 1993. Velocity and spectral characteristics of the volcanic tremor at Etna deduced by a small seismometer array. J. Volcanol. Geotherm. Res. 56, 369–378.
Del Pezzo, E., La Rocca, M., Ibanez, J., 1997. Observation of highfrequency scattered waves using dense arrays at Teide volcano. Bull. Seismol. Soc. Am. 87, 1637–1647.
Ferrucci, F., Godano, C., Pino, N.A., 1990. Approach to the volcanic tremor by the covariance analysis: application to the 1989 eruption of Mt. Etna (Sicily). Geophys. Res. Lett. 17, 2425–2428.
Frankel, A., Hough, S., Friberg, P., Busby, R., 1991. Observations of Loma Prieta aftershocks from a dense array in Sunnywale. Bull. Seismol. Soc. Am. 80, 1900–1922.
Goldstein, P., Archuleta, R.J., 1987. Array analysis of seismic signals. Geophys. Res. Lett. 14, 13– 16.
Goldstein, P., Archuleta, R.J., 1991. Deterministic frequencywavenumber methods and direct measurements of rupture propagation during earthquakes using a dense array: theory and methods. J. Geophys. Res. 96, 6173– 6185.
Goldstein, P., Chouet, B., 1994. Array measurements and modelling of a source of shallow volcanic tremor at Kilauea Volcano,
Hawaii. J. Geophys. Res. 99, 2637– 2652.
Gresta, S., Imposa, S., Patane`, D., Patane`, G., 1987. Volcanic tremor at Mt. Etna: state-of-the-art and perspectives. Pure Appl. Geophys. 125, 255– 271.
Guerra, I., Lo Bascio, D., Luongo, G., Scarpa, R., 1976. Seismic activity accompanying the 1974 eruption of Mt. Etna. J. Volcanol. Geotherm. Res. 1, 347– 362.
Herrmann, R.B., 1987. Surface Waves Inversion Programs St. Louis University, Missouri.
Kanasewich, E.R., 1981. Time Sequence Analysis in Geophysics. University of Alberta Press, Edmonton, pp. 1 – 532.
Metaxian, J.P., Lesage, P., Dorel, J., 1997. Permanent tremor of Masaya volcano, Nicaragua: wave field analysis and source location. J. Geophys. Res. 102, 22529– 22545.
Metaxian, J.P., Lesage, P., Valette, B., 2002. Locating sources of volcanic tremor and emergent events by seismic triangulation: application to Arenal Volcano, Costa Rica. J. Geophys. Res. 107
10. 1029/2001JB000559.
Neuberg, J., Luckett, R., Ripepe, M., Braun, T., 1994. Highlights from a seismic broadband array on Stromboli Volcano. Geophys. Res. Lett. 21, 749–752.
Ohminato, T., Chouet, B.A., 1997. A free-surface boundary condition for including 3D topography in the finite-difference method. Bull. Seismol. Soc. Am. 87, 494–515.
Privitera, E., Sgroi, T., Gresta, S., 2003. Statistical analysis of intermittent volcanic tremor associated with the September 1989 summit explosive eruptions at Mt. Etna, Sicily. J. Volcanol. Geotherm. Res. 120, 235– 247.
Ripepe, M., Coltelli, M., Privitera, E., Gresta, S., Moretti, M., Piccinini, D., 2001. Seismic and infrasonic evidences for an impulsive source of the shallow volcanic tremor at Mt. Etna, Italy. Geophys. Res. Lett. 28, 1701–1704.
Ripperger, J., Igel, H., Wassermann, J., 2003. Seismic wave simulation in the presence of real volcano topography. J. Volcanol. Geotherm. Res. 128, 31– 44.
Riuscetti, M., Schick, R., Seidl, D., 1977. Spectral parameters of volcanic tremor at Etna. J. Volcanol. Geotherm. Res. 2, 289–298.
Saccorotti, G., Chouet, B.A., Martini, M., Scarpa, R., 1998. Bayesian Statistics applied to the location of the source of explosions at Stromboli volcano, Italy. Bull. Seismol. Soc. Am. 5, 1099– 1111.
Saccorotti, G., Chouet, B.A., Dawson, P.B., 2001a. Wavefield properties of a shallow long-period event and tremor at Kilauea Volcano, Hawaii. J. Volcanol. Geotherm. Res. 109, 163– 189.
Saccorotti, G., Almendros, J., Carmona, E., Ibanez, J., Del Pezzo, E., 2001b. Slowness anomalies from two dense seismic arrays at
Deception Island Volcano, Antarctica. Bull. Seismol. Soc. Am. 91, 561– 571.
Saccorotti, G., Chouet, B.A., Dawson, P.B., 2003. Shallow velocity models at Kilauea Volcano, Hawaii, determined from array analyses of tremor wavefield. Geophys. J. Int. 152, 633– 648.
Schick, R., Riuscietti, M., 1973. An analysis of volcanic tremors at South Italian volcanoes. Z. Geophys. 39, 247–262.
Schick, R., Cosentino, M., Lombardo, G., Patane`, G., 1982. Volcanic tremor at Mt. Etna. A brief description. Mem. Soc. Geol. Ital. 23, 191–196.
Schmidt, R.O., 1986. Multiple emitter location and signal parameter estimation. IEEE Trans. Antennas Propag. 34, 276–280.
Seidl, D., Schick, R., Riuscetti, M., 1981. Volcanic tremors at Etna: a model for hydraulic origin. Bull. Volcanol. 44, 43– 56.
Wang, H., Kaveh, M., 1985. Coherent signal-subspace processing for the detection and estimation of angles of arrival of multiple
wide-band sources. IEEE Trans. ASSP 33, 823– 831.
Wassermann, J., Ohrnberger, M., 2001. Automatic hypocenter. determination of volcano induced seismic transients based on wavefield coherence—an application to the 1998 eruption of Mt. Merapi, Indonesia. J. Volcanol. Geotherm. Res. 110, 57– 77.
Wegler, U., Seidl, D., 1997. Kinematic parameters of the tremor wavefield at Mt. Etna (Sicily). Geophys. Res. Lett. 24, 759–762.
Almendros, J., Chouet, B.A., Dawson, P.B., 2001a. Spatial extent of a hydrothermal system at Kilauea Volcano, Hawaii, determined from array analyses of shallow long-period seismicity: 1. Method. J. Geophys. Res. 106, 13565– 13580.
Almendros, J., Chouet, B.A., Dawson, P.B., 2001b. Spatial extent of a hydrothermal system at Kilauea Volcano, Hawaii, determined from array analyses of shallow long-period seismicity: 2. Results. J. Geophys. Res. 106, 13581–13597.
Almendros, J., et al., 2002. Mapping the sources of the seismic wavefield at Kilauea Volcano, Hawaii, using data recorded on multiple seismic antenna. Bull. Seismol. Soc. Am. 92, 2333–2351.
Aki, K., 1957. Space and time spectra of stationary stochastic waves, with special reference to microtremors. Bull. Earthq.
Res. Inst. Univ. Tokyo 25, 415–457.
Aki, K., 1959. Correlation study of near earthquake waves. Bull. Earthq. Res. Inst. Univ. Tokyo 37, 207– 232.
Aki, K., Chouet, B., Fehler, M., Zandt, G., Koyanagi, R., Colp, J., Hay, R.G., 1978. Seismic properties of a shallow magma reservoir in Kilauea Iki by active and passive experiments. J. Geophys. Res. 83, 2273–2282.
Benoit, J., McNutt, S.R., 1997. New constraints on the source processes of volcanic tremor at Arenal volcano, Costa Rica, using broadband seismic data. Geophys. Res. Lett. 24, 449– 452.
Calvari, S., Neri, M., Pinkerton, H., 2002. Effusion rate estimations during the 1999 summit eruption on Mount Etna, and growth of two distinct lava flow fields. J. Volcanol.Geotherm. Res. 119, 107– 123.
Castellano, M., Capello, M., Del Pezzo, E., Giudicepietro, F., La Rocca, M., Martini, M., Petrosino, S., Saccorotti, G., Ibanez, J., Abril, M., Almendros, J., Carmona, E., Martinez, C., Vilchez, J., Privitera, E., Alparone, S., Di Grazia, G., Gresta, S., 2000. A double seismic array experiment on Mt. Etna. Osservatorio Vesuviano Open file report n. 2-2000, 30 pp. (available on line at Http://www.ov.ingv.it/italiano/pubblicazioni/openfile/ofr_02_00.htm).
Chiou, S.J., Bolt, B.A., 1993. Seismic wave slowness-vector estimation from broad-band array data. Geophys. J. Int. 114, 234– 248.
Chouet, B.A., 1988. Resonance of a fluid-driven crack: radiation properties and implications for the source of long-period events and harmonic tremor. J. Geophys. Res. 93, 4375– 4400.
Chouet, B.A., Saccorotti, G., Martini, M., Dawson, P.B., De Luca, G., Milana, G., Scarpa, R., 1997. Source and path effects in the wavefields of tremor and explosions at Stromboli volcano, Italy. J. Geophys. Res. 102, 15129– 15150.
Del Pezzo, E., De Martino, S., Gresta, S., Martini, M., Milana, G., Patane`, D., Sabbarese, C., 1993. Velocity and spectral characteristics of the volcanic tremor at Etna deduced by a small seismometer array. J. Volcanol. Geotherm. Res. 56, 369–378.
Del Pezzo, E., La Rocca, M., Ibanez, J., 1997. Observation of highfrequency scattered waves using dense arrays at Teide volcano. Bull. Seismol. Soc. Am. 87, 1637–1647.
Ferrucci, F., Godano, C., Pino, N.A., 1990. Approach to the volcanic tremor by the covariance analysis: application to the 1989 eruption of Mt. Etna (Sicily). Geophys. Res. Lett. 17, 2425–2428.
Frankel, A., Hough, S., Friberg, P., Busby, R., 1991. Observations of Loma Prieta aftershocks from a dense array in Sunnywale. Bull. Seismol. Soc. Am. 80, 1900–1922.
Goldstein, P., Archuleta, R.J., 1987. Array analysis of seismic signals. Geophys. Res. Lett. 14, 13– 16.
Goldstein, P., Archuleta, R.J., 1991. Deterministic frequencywavenumber methods and direct measurements of rupture propagation during earthquakes using a dense array: theory and methods. J. Geophys. Res. 96, 6173– 6185.
Goldstein, P., Chouet, B., 1994. Array measurements and modelling of a source of shallow volcanic tremor at Kilauea Volcano,
Hawaii. J. Geophys. Res. 99, 2637– 2652.
Gresta, S., Imposa, S., Patane`, D., Patane`, G., 1987. Volcanic tremor at Mt. Etna: state-of-the-art and perspectives. Pure Appl. Geophys. 125, 255– 271.
Guerra, I., Lo Bascio, D., Luongo, G., Scarpa, R., 1976. Seismic activity accompanying the 1974 eruption of Mt. Etna. J. Volcanol. Geotherm. Res. 1, 347– 362.
Herrmann, R.B., 1987. Surface Waves Inversion Programs St. Louis University, Missouri.
Kanasewich, E.R., 1981. Time Sequence Analysis in Geophysics. University of Alberta Press, Edmonton, pp. 1 – 532.
Metaxian, J.P., Lesage, P., Dorel, J., 1997. Permanent tremor of Masaya volcano, Nicaragua: wave field analysis and source location. J. Geophys. Res. 102, 22529– 22545.
Metaxian, J.P., Lesage, P., Valette, B., 2002. Locating sources of volcanic tremor and emergent events by seismic triangulation: application to Arenal Volcano, Costa Rica. J. Geophys. Res. 107
10. 1029/2001JB000559.
Neuberg, J., Luckett, R., Ripepe, M., Braun, T., 1994. Highlights from a seismic broadband array on Stromboli Volcano. Geophys. Res. Lett. 21, 749–752.
Ohminato, T., Chouet, B.A., 1997. A free-surface boundary condition for including 3D topography in the finite-difference method. Bull. Seismol. Soc. Am. 87, 494–515.
Privitera, E., Sgroi, T., Gresta, S., 2003. Statistical analysis of intermittent volcanic tremor associated with the September 1989 summit explosive eruptions at Mt. Etna, Sicily. J. Volcanol. Geotherm. Res. 120, 235– 247.
Ripepe, M., Coltelli, M., Privitera, E., Gresta, S., Moretti, M., Piccinini, D., 2001. Seismic and infrasonic evidences for an impulsive source of the shallow volcanic tremor at Mt. Etna, Italy. Geophys. Res. Lett. 28, 1701–1704.
Ripperger, J., Igel, H., Wassermann, J., 2003. Seismic wave simulation in the presence of real volcano topography. J. Volcanol. Geotherm. Res. 128, 31– 44.
Riuscetti, M., Schick, R., Seidl, D., 1977. Spectral parameters of volcanic tremor at Etna. J. Volcanol. Geotherm. Res. 2, 289–298.
Saccorotti, G., Chouet, B.A., Martini, M., Scarpa, R., 1998. Bayesian Statistics applied to the location of the source of explosions at Stromboli volcano, Italy. Bull. Seismol. Soc. Am. 5, 1099– 1111.
Saccorotti, G., Chouet, B.A., Dawson, P.B., 2001a. Wavefield properties of a shallow long-period event and tremor at Kilauea Volcano, Hawaii. J. Volcanol. Geotherm. Res. 109, 163– 189.
Saccorotti, G., Almendros, J., Carmona, E., Ibanez, J., Del Pezzo, E., 2001b. Slowness anomalies from two dense seismic arrays at
Deception Island Volcano, Antarctica. Bull. Seismol. Soc. Am. 91, 561– 571.
Saccorotti, G., Chouet, B.A., Dawson, P.B., 2003. Shallow velocity models at Kilauea Volcano, Hawaii, determined from array analyses of tremor wavefield. Geophys. J. Int. 152, 633– 648.
Schick, R., Riuscietti, M., 1973. An analysis of volcanic tremors at South Italian volcanoes. Z. Geophys. 39, 247–262.
Schick, R., Cosentino, M., Lombardo, G., Patane`, G., 1982. Volcanic tremor at Mt. Etna. A brief description. Mem. Soc. Geol. Ital. 23, 191–196.
Schmidt, R.O., 1986. Multiple emitter location and signal parameter estimation. IEEE Trans. Antennas Propag. 34, 276–280.
Seidl, D., Schick, R., Riuscetti, M., 1981. Volcanic tremors at Etna: a model for hydraulic origin. Bull. Volcanol. 44, 43– 56.
Wang, H., Kaveh, M., 1985. Coherent signal-subspace processing for the detection and estimation of angles of arrival of multiple
wide-band sources. IEEE Trans. ASSP 33, 823– 831.
Wassermann, J., Ohrnberger, M., 2001. Automatic hypocenter. determination of volcano induced seismic transients based on wavefield coherence—an application to the 1998 eruption of Mt. Merapi, Indonesia. J. Volcanol. Geotherm. Res. 110, 57– 77.
Wegler, U., Seidl, D., 1997. Kinematic parameters of the tremor wavefield at Mt. Etna (Sicily). Geophys. Res. Lett. 24, 759–762.
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