Graduation Year

2023

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

School of Geosciences

Major Professor

Stephen R. McNutt, Ph.D.

Co-Major Professor

Glenn Thompson, Ph.D.

Committee Member

Jochen Braunmiller, Ph.D.

Committee Member

Aurelie Germa, Ph.D.

Committee Member

Michael E. West, Ph.D.

Keywords

Lastarria, PLUTONS Project, seismology, volcano

Abstract

The following dissertation is a study of three seismological techniques used to determine the geophysical properties of two large, inflating magma bodies in the upper crust in South America: one under Uturuncu volcano and one beneath Lastarria and Cordon del Azufre volcanoes. First, I use the method of teleseismic receiver functions to image the top and bottom of the magma body beneath Uturuncu volcano. Depths to the top of this body vary between 6 and 12 km below sea level, while depths to the bottom vary between 13 and 22 km below sea level, with the thickness ranging from 6 to 15 km. Then, I compute hypocenters and classify the earthquakes occurring between Lastarria and Cordon del Azufre volcanoes to determine if a magma body between them is priming for eruption or if it may be feeding a shallower magma chamber beneath Lastarria. My classification scheme consisted of five types of seismic events: volcano-tectonic, long period type 1, long period type 2, hybrid, and unknown. The majority of these events are above 10 km below sea level, and most are near Lastarria. I determine that this seismic activity is due to mobile gases and fluids. Finally, I use an attenuation method to study the heterogeneity of the crust between Uturuncu volcano and the magma body beneath it. The assumptions of the method used are undermined by the variability of the earthquake sources and their spectra as well as by extreme geological heterogeneity of this location.

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