Temporal change in coda Q at Nevado Del Ruiz Volcano, Colombia

Londoño, John Makario

doi:10.1016/0377-0273(95)00084-4

Cited by 18 publications

(26 citation statements)

References 25 publications

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“…Using the diffusion model for single mode, Wegler and Luhr [2001] estimated a mean free path of the order of 0.1 km for S wave at shallow depth of the Merapi volcano in the frequency band of 4-20 Hz from an active seismic experiment. Using the multiple lapse time analysis, Londono [1996] estimated a mean free path of about 10 km in the frequency band of 6-24 Hz at Nevado Del Ruiz volcano, Colombia, using volcanotectonic earthquakes.…”

Section: Estimation Of the Scattering Coefficientsmentioning

confidence: 99%

Multiple scattering and mode conversion revealed by an active seismic experiment at Asama volcano, Japan

Yamamoto¹,

Sato²

2010

J. Geophys. Res.

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[1] Volcanoes are one of the most heterogeneous fields in the Earth's crust, and the understanding of such inhomogeneities may provide us important information on various volcanic processes. In the previous studies on the seismic wave propagation at active volcanoes, the diffusion model has been widely used to model the energy transportation and the contribution of P and S waves and their mode conversion have not been well recognized partly due to lack of dense observations capturing spatiotemporal pattern of energy propagation. In this study, we present observational evidence of mode conversions and multiple scattering at Asama volcano, Japan, revealed by an active seismic experiment with a dense seismic network. The observed spatial distribution of propagating energy emitted from the explosive P source shows a wavefront of direct P wave and a pattern exhibiting two slopes which is indicative of multiple scattering and conversion scattering of two modes having different scattering coefficients. These facts suggest that the radiative transfer theory is more preferable than the diffusion theory to explain the observed characteristics. We thus modeled the energy propagation using the radiative transfer theory assuming multiple isotropic scattering including conversion scatterings and quantitatively estimated scattering parameters. Estimated total scattering coefficients for P-to-S and S-to-S scattering are about three times larger than that of P-to-P scattering, and the mean free path of S wave is about 1 km for an 8-16 Hz band. These results suggest that the mode conversion and multiple scattering have an indispensable effect on the seismic energy propagation in heterogeneous volcanic environments.Citation: Yamamoto, M., and H. Sato (2010), Multiple scattering and mode conversion revealed by an active seismic experiment at Asama volcano, Japan,

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Section: Estimation Of the Scattering Coefficientsmentioning

confidence: 99%

Multiple scattering and mode conversion revealed by an active seismic experiment at Asama volcano, Japan

Yamamoto¹,

Sato²

2010

J. Geophys. Res.

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“…Many authors reported local-earthquake coda attenuation (Q c ) varying over time scales from several weeks to a few years, such as Chouet (1976Chouet ( , 1979, Aki (1980), Stewart et al (1983), Rhea (1984), Novelo-Casanova et al (1985), , Jin and Aki (1986), Peng et al (1986), ), Fehler et al (1988, Londono (1996), Gusev (1997), Del Pezzo et al (2004, Moncayo et al (2004), Novelo-Casanova et al (2006). The results were invariably interpreted by using the single-and multiple-scattering coda models, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…By contrast to non-volcanic regions where strong frequency dependencies with  ≈ 1 are common (e.g., Roecker et al 1982), frequency dependencies of the volcanic Q c vary from weak (Chouet, 1976;Fehler et al, 1988) to strong (e.g., Londono, 1996;Moncayo et al, 2004). No widely accepted theory exists to explain these variations, and particularly the weak frequency dependence of Q c at volcanoes.…”

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confidence: 99%

“…In many studies, temporal variations of coda Q c were studied at volcanoes (e.g., Chouet, 1976;Fehler et al, 1988;Londono, 1996;Moncayo et al, 2004, NoveloCasanova et al, 2006Del Pezzo et al 2004). In these cases, the key observed coda characteristics are usually the temporal variations of the values of Q c at selected frequencies and also the dependencies of Q c on frequency.…”

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confidence: 99%

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Temporal variations of coda Q: An attenuation-coefficient view

Morozov

2011

Physics of the Earth and Planetary Interiors

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Spatial and temporal variations of coda wave attenuation were identified in many studies, and particularly in relation to major earthquakes and volcanic eruptions. Both the coda quality factor, Q c , and its frequency dependence often change following such events, which is often attributed to variations in the properties of large volumes of the subsurface. However, Q c is also strongly sensitive to the assumed theoretical models, which are usually insufficiently accurate for constraining the actual relationships between the geometrical spreading, anelastic dissipation, and scattering. This inaccuracy often leads to significant exaggeration of attenuation effects and complicates the interpretation of temporal variations. To resolve this problem, this study uses a phenomenological approach based on the temporal attenuation coefficient  instead of Q c . The attenuation coefficient often linearly depends on frequency f, with intercept  = (0) related to the geometrical spreading and slope giving the "effective quality" factor Q e as d/df = Q e and Q e changed from 400 before the eruption to 750 after it. The observed temporal variations are explained by the near-surface changes caused by seasonal variations in the non-volcanic case and gas-, magma-, and geothermal-system related in the volcanic case.Scattering attenuation does not appear to be a significant factor in these areas, or otherwise it may be indistinguishable due to its fundamental trade-off with the background structure and anelastic attenuation in the data.

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“…Studies of coda Q have been made at Nevado del Ruiz Volcano (NRV), suggesting that the coda Q seems to be a good premonitory tool for volcanic activity (Londoño 1996;Londoño et al 1998). However, the use of Q as part of a warning model before the occurrence of a volcanic crisis has not yet been analyzed.…”

Section: Introductionmentioning

confidence: 99%

A warning model based on temporal changes of coda Q for volcanic activity at Nevado Del Ruiz Volcano, Colombia

Londoño

Sudo

2002

Bull Volcanol

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The coda Q has been calculated for Nevado del Ruiz Volcano, Colombia (NRV) from 1985 to 1999 by using a single scattering model. During this period, the inverse of Q (Q -1 proportional to attenuation) exhibited a long-term decrease with time, as well as shorterterm variations related to the volcanic activity. Q -1 increased prior to volcanic crises and decreased afterward. Based on these observations, a seismic warning criterion has been developed. The parameters (frequency band, size of moving average window, and threshold levels) necessary to evidence clear and significant short-term changes in Q -1 have been investigated and appropriated values are proposed. We suggest a phenomenological model with three stages for the short-term temporal changes in Q -1 at NRV. Firstly, Q -1 increases before a volcanic crises because of accumulation of gas and/or liquid, which decreases the aspect ratio of fluid pockets and increases the fractional volume of fluid in the rocks and the pore aspect ratio. Secondly, Q -1 starts to decrease during the crises by the discharging of fluids such as gas, water, etc. from the volcano. Finally, Q -1 becomes more stable after the crisis at a lower value because of the degassing and/or increasing of rigidity of the medium because of the long-term crystallization and cooling processes. Q -1 seems to be a promising monitoring tool at NRV. It is possible that the observed temporal changes of Q -1 , combined with other parameters, may help to predict with greater accuracy a volcanic crisis at NRV.Keywords Coda Q · Fluid aspect ratio · Pore aspect ratio · Seismicity · Volcanic activity Method, data, and processingThe method used to calculate coda Q in this study is based on the assumption that coda waves are single S to Editorial responsibility: J.-F. Lénat

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Temporal change in coda Q at Nevado Del Ruiz Volcano, Colombia

Cited by 18 publications

References 25 publications

Multiple scattering and mode conversion revealed by an active seismic experiment at Asama volcano, Japan

Multiple scattering and mode conversion revealed by an active seismic experiment at Asama volcano, Japan

Temporal variations of coda Q: An attenuation-coefficient view

A warning model based on temporal changes of coda Q for volcanic activity at Nevado Del Ruiz Volcano, Colombia

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