Show simple item record

dc.contributor.authorAlvizuri, Celso R.
dc.date.accessioned2017-02-15T21:20:51Z
dc.date.available2017-02-15T21:20:51Z
dc.date.issued2016-12
dc.identifier.urihttp://hdl.handle.net/11122/7316
dc.descriptionThesis (Ph.D.) University of Alaska Fairbanks, 2016en_US
dc.description.abstractWe present a catalog 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 broadband 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 six-dimensional 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 catalog: (1) 6 isotropic events, (2) 5 tensional crack events, and (3) a swarm of 14 events southeast of the volcanic center 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. A seismic moment tensor is a 3×3 symmetric matrix that provides a compact representation of a seismic source. We develop an algorithm to estimate moment tensors and their uncertainties from observed seismic data. For a given event, the algorithm performs a grid search over the six-dimensional space of moment tensors by generating synthetic waveforms for each moment tensor and then evaluating a misfit function between the observed and synthetic waveforms. 'The' moment tensor M₀ for the event is then the moment tensor with minimum misfit. To describe the uncertainty associated with M₀, we first convert the misfit function to a probability function. The uncertainty, or rather the confidence, is then given by the 'confidence curve' P(V), where P(V) is the probability that the true moment tensor for the event lies within the neighborhood of M that has fractional volume V. The area under the confidence curve provides a single, abbreviated 'confidence parameter' for M0. We apply the method to data from events in different regions and tectonic settings: 63 small (Mw <2.5) events at Uturuncu volcano in Bolivia, 21 moderate (Mw >4) earthquakes in the southern Alaska subduction zone, and 12 earthquakes and 17 nuclear explosions at the Nevada Test Site. Characterization of moment tensor uncertainties puts us in better position to discriminate among moment tensor source types and to assign physical processes to the events.en_US
dc.language.isoen_USen_US
dc.titleEstimation of full moment tensors, including uncertainties, for earthquakes, volcanic events, and nuclear explosionsen_US
dc.typeThesisen_US
dc.type.degreephden_US
dc.identifier.departmentDepartment of Geosciencesen_US
dc.contributor.chairTape, Carl
dc.contributor.committeeChristensen, Douglas
dc.contributor.committeeWest, Michael
dc.contributor.committeeFreymueller, Jeffrey
refterms.dateFOA2020-03-06T01:57:54Z


Files in this item

Thumbnail
Name:
Alvizuri_C_2016.pdf
Size:
64.38Mb
Format:
PDF
Description:
Thesis
Thumbnail
Name:
Alvizuri_C_2016.zip
Size:
34.21Mb
Format:
Unknown

This item appears in the following Collection(s)

Show simple item record