Date of Award

2016

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Geophysics (MS)

Administrative Home Department

Department of Geological and Mining Engineering and Sciences

Advisor 1

Gregory Waite

Committee Member 1

Chad Deering

Committee Member 2

Rudiger Escobar-Wolf

Abstract

Pacaya volcano is a basaltic complex in the Central American Volcanic Arc in Guatemala. Pacaya has been in an open vent condition since 1961. During January 2015 we deployed 19 short period seismometer stations on Pacaya at distances less than 1.5 kilometers from the summit. The resulting data consisted of tremor and thousands of discrete events associated with ongoing outgassing. Where possible, individual events were identified and located. They were found to be high in the edifice near the vent. We used the decaying codas of these events to model the attenuation structure of the Pacaya edifice, following the energy density decay method of Aki and Chouet [1975]. We attempted to model the attenuation coda quality factor, Qc, at 482 events that were well recorded by the temporary network. After investigating a range of frequencies, we found a range of 2-10 Hz to be the best frequency range in terms of the frequency ranges analyzed. We found that there was not a significant dependence of Qc on P or S wave amplitude, so did not attempt to include a source term correction. Median Qc, selected using thresholds, ranged from as low as 146 at station PS12 to 194 at station PS06. In general, attenuation was lower at the western-most stations. We also interpreted that higher attenuation to the north and on the north summit may result from fracturing or magmatic sources and that the lower attenuation to the west may be related to the slide and subsidence that occurred.

Download

Share

COinS