Analyses of unusual long-period earthquakes with extended coda recorded at Katmai National Park, Alaska, USA

Silvio De Angelis

doi:10.1029/2005gl025581

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Analyses of unusual long-period earthquakes with extended coda recorded at Katmai National Park, Alaska, USA

Silvio De Angelis

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Abstract

A swarm of six long-period (LP) events with slowly decaying coda wave amplitudes and durations up to 120 s, was recorded by seismic stations located in the proximity of Mt. Griggs, a fumarolically active volcano in the Katmai National Park, Alaska, during December 8–21, 2004. Spectral analyses reveal the quasi-monochromatic character of the waveforms, dominated by a 2.5 Hz mode frequently accompanied by a weaker high-frequency onset (6.0–9.0 Hz). Particle motion azimuths and inclination angles show a dominant WNW-ESE direction of polarization for all the signals, and suggest that seismic energy is radiated by a stable source at shallow depth. Damping coefficients between 0.0014 and 0.0063 are estimated by fitting an exponential decay model to the signal's coda; corresponding quality factors range from 78 to 351. The source of the waveforms is modelled as a resonant cavity filled with a fluid/gas mixture.

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Source-reported bounding extent: 58.1° to 58.5° latitude; -155.4° to -154.8° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Silvio De Angelis. 2006-04-05. Analyses of unusual long-period earthquakes with extended coda recorded at Katmai National Park, Alaska, USA. https://doi.org/10.1029/2005gl025581

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