Journal Article

Full moment tensors for small events (Mw < 3) at Uturuncu volcano, Bolivia

Celso Alvizuri and Carl Tape

in Geophysical Journal International

Volume 206, issue 3, pages 1761-1783
ISSN: 0956-540X
Published online July 2016 | e-ISSN: 1365-246X | DOI:

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We present a catalogue of full seismic moment tensors for 63 events from Uturuncu volcano in Bolivia. The events were recorded during 2011–2012 in the PLUTONS seismic array of 24 broad-band stations. Most events had magnitudes between 0.5 and 2.0 and did not generate discernible surface waves; the largest event was Mw 2.8. For each event we computed the misfit between observed and synthetic waveforms, and we used first-motion polarity measurements to reduce the number of possible solutions. Each moment tensor solution was obtained using a grid search over the 6-D space of moment tensors. For each event, we show the misfit function in eigenvalue space, represented by a lune. We identify three subsets of the catalogue: (1) six isotropic events, (2) five tensional crack events, and (3) a swarm of 14 events southeast of the volcanic centre that appear to be double couples. The occurrence of positively isotropic events is consistent with other published results from volcanic and geothermal regions. Several of these previous results, as well as our results, cannot be interpreted within the context of either an oblique opening crack or a crack-plus-double-couple model. Proper characterization of uncertainties for full moment tensors is critical for distinguishing among physical models of source processes.

Keywords: Inverse theory; Earthquake source observations; Volcano seismology; South America

Journal Article.  14084 words.  Illustrated.

Subjects: Volcanology and Seismology