Physical Sciences and Mathematics Commons^™

Applications Of Observational Seismology: Insights Into Volcanic And Near Surface Processes, Justin T. Wilgus

Earth and Planetary Sciences ETDs

The field of observational seismology has made tremendous progress in the past two decades. This progress has been multi-faceted in form, but significant contributions emanated from 1) increases in both the quality and the quantity of seismic data 2) advances in computational power 3) advances in algorithmic capability, including machine learning. In this dissertation I report on three distinctly different seismic applications made possible by the aforementioned progress and discuss the insights these applications have provided in understanding volcanic and near surface processes of the Earth.

In the first chapter titled, “Shear Velocity Evidence of Upper Crustal Magma Storage Beneath …

Seismic Analysis Of The Upper & Lower Falls Of The Yellowstone River, Loring Schaible

Earth and Planetary Sciences ETDs

Twelve years of concurrent hydrologic and continuous seismic data along with temporary seismic data demonstrate that the Upper and Lower Falls of the Grand Canyon of the Yellowstone River comprise a highly localized source of 0.5-5 Hz seismic energy that overwhelms anthropogenic contributions. In aggregate, seismic amplitude from 2008-2019 is linearly related to discharge with a correlation coefficient of 0.96. Repeated deviations from this linear relationship persist for 1-2 weeks prior to the date that Yellowstone Lake becomes clear of winter ice coverage. Seismic efficiency increases by ~50-250% during this period of ice-breakup, during which lake ice flows into the …

Seismic Shadow Zone Investigation In The Upper Magma Reservoir Of The Yellowstone Caldera, Sarah Nolt-Caraway

Earth and Planetary Sciences ETDs

This study investigates whether the Yellowstone Caldera has enough melt to mute S-waves, creating a seismic shadow zone. Using a dense nodal deployment of ~650 stations, 7-9 earthquakes during the nodal deployment, and 21 broadband stations with 3,000-4,000 events per station; amplitude and noise maps, seismograms, and automatic phase picks probabilities from a deep learning model were analyzed to assess the potential role of melt, crustal attenuation, and noise in affecting body waves, particularly S-phases. The results are inconclusive, with unclear evidence whether observed amplitude decay is normal signal decay due to distance, noise-related, melt, or from scattering and intrinsic …

A Seismic Investigation Of Uturuncu Volcano And The Lazufre Volcanic Complex, Heather L. Mcfarlin

USF Tampa Graduate Theses and Dissertations

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 …

Induced Seismicity In The Raton Basin And Global Variability Of The 410-Km Discontinuity, Margaret E. Glasgow

Earth and Planetary Sciences ETDs

Natural processes like mantle convection and plate tectonics dominate Earth’s seismic structure. Recently human activities have increasingly influenced the deformation of the shallow crust. In this dissertation, passive source seismology was used to constrain seismic discontinuities in the mantle transition zone and seismogenic structures in induced earthquake settings. Using a novel sampling method and uniform processing approach, I found the 410-km discontinuity is thermally and compositionally variable. Using a machine- learning approach, I found the three main zones of seismicity in the Raton Basin consist of short faults or fault segments with variable orientations. The zone that hosted a Mw …

Machine-Learning Reveals Aftershock Locations For Three Idaho Earthquake Sequences, Spencer F. Wilbur

Boise State University Theses and Dissertations

I explore spatial and temporal aftershock patterns related to three instrumentally recorded earthquakes in Idaho -- the Sulphur Peak, the Challis, and the Stanley earthquakes. These three M > 5 earthquakes border the eastern Snake River Plain and lie within the Intermountain Seismic Belt and Centennial Tectonic Belt. Using machine learning for event detection and phase picking from local and regional seismic networks, I generate new aftershock catalogs. I locate more aftershocks than in the USGS catalog due to lower signal-to-noise detections. Using my phase picks, I locate aftershocks using a range of velocity models and select a catalog that represents …

An Assessment Of The Performance Of The Earthscope Automated Receiver Survey: A User’S Guide To Ears., Erin L. Taxon

Theses and Dissertations

An Assessment of the Performance of the EarthScope Automatic Receiver Survey: A User's Guide to EARS.

With the advent of digital seismic recording, the ability to process and interpret large quantities of seismic data has become increasingly vital. EarthScope Automated Receiver Survey, EARS, was launched in 2005 to estimate bulk crustal properties in real time, at all broadband seismograph stations, globally. EARS utilizes the receiver function HK stacking method to estimate a station’s crustal thickness (H) and ratio of P wave velocity (Vp) and S wave velocity (Vs), known as Vp/Vs (K). Receiver function analysis observes the arrival times …

Observational Constraints On The 520 Km Mantle Discontinuity, Mantle Transition Zone Anisotropy, And Local Seismicity At Mount St. Helens, Han Zhang

Earth and Planetary Sciences ETDs

Seismology provides valuable observational constraints to thermal and compositional states at inaccessible depths via understanding how elastic wave propagating through them. While many of fundament questions regarding solid Earth structures have been addressed during its more than 100 years history, some details remain unfilled and carefully designed approaches are needed to complete the pictures. This dissertation contributes observational constraints on three topics with newly developed methods. 1) We detected a controversial mantle discontinuity at about 520 km and concluded a mean mantle composition close to the Pyrolite model based on its seismic properties. 2) We isolated anisotropic effects in mantle …

Analysis Of Aftershock Parameters For The Alaskan Subduction Zone Tectonic Region, Gabrielle M. Paris

Geology Undergraduate Honors Theses

Forecasting how many earthquakes will occur following a potentially damaging earthquake helps the public and emergency operators stay safe and make informed decisions. The U.S. Geological Survey issues aftershock forecasts following potentially damaging earthquakes, using models to predict the number of earthquakes that should occur within the next day, week, month, and year with 95% confidence to reflect the uncertainty in aftershock behavior. The USGS considers the forecast to be "successful" when the number of earthquakes observed within the forecasted time period is within the 95% confidence interval. For aftershock sequences that occur along the forearc of the Alaskan subduction …

Application Of Machine Learning In Geophysics: Ranking Teleseismic Shear Wave Splitting Measurements And Classifying Different Types Of Earthquakes, Yanwei Zhang

Doctoral Dissertations

"During the past decades, applications of Machine Learning have been explosively developed to solve various academic and industrial problems, and over-human performance has been shown in diverse areas. In geophysical research, Machine Learning, especially Convolutional Neural Network (CNN), has been applied in numerous studies and demonstrated considerable potential. In this study, we applied CNN to solve two geophysical problems, ranking teleseismic shear splitting (SWS) measurements and classifying different types of earthquakes.

For ranking teleseismic SWS measurements, we utilized a CNN-based method to automatically select reliable SWS measurements. The CNN was trained by human-verified teleseismic SWS measurements and tested using synthetic …

To Erupt Or Not To Erupt? That Is The Question: Extremely High Levels Of Background Seismicity And Lack Of Eruptivity From 2003-2019 At Gareloi Volcano, Aleutian Islands, Alaska, Kiana Tamarie Harris

WWU Graduate School Collection

Mount Gareloi, one of the westernmost volcanoes in the Aleutian arc, has not erupted since 1989, yet it continuously exhibits extremely high levels of background seismicity. Hundreds of volcanic earthquakes are recorded per day on the island since seismometer installation in 2003. I analyzed and classified seismic data collected from 2003-2019 to explore the geophysical processes causing this consistent seismicity with no subsequent eruptive activity. Analysis of waveform and corresponding spectra indicate the vast majority of Gareloi earthquakes are characterized by frequencies between 1 and 5 Hz, which are typical of long-period (LP) events, and these events are particularly dominant …

Seismic Attenuation, Time Delays And Raypath Bending Of Teleseisms Beneath Uturuncu Volcano, Bolivia, Alexandra K. Farrell

USF Tampa Graduate Theses and Dissertations

A set of 14 teleseismic earthquakes was studied to determine how wave propagation was affected by a presumed magma body beneath Uturuncu volcano, Bolivia. Teleseisms are suitable for study because they are relatively long period, contain purely P waves, and have near-vertical incidence angles. The number of events is small but the events have good signal-to-noise ratios and very similar waveforms for each event so that reliable measurements could be made of arrival times and amplitudes. Attenuation of amplitudes occurs in a NW-SE trend beneath the volcano, 14 by 34 km (long axis NW-SE). Calculated values of the quality factor …

Body Wave Analysis For Low-Angle Thrust Quakes On Titan: Implications For Dragonfly, John William Owens

Graduate Research Theses & Dissertations

Little is known of the structure and seismic nature of planetary bodies that have an outer shell of ice instead of a rocky crust. These bodies are called icy satellites and one such body, Saturn’s moon Titan, is unique because of its thick atmosphere, methane cycle, and assumed salty subsurface ocean. NASA’s Dragonfly mission, set to launch in 2026, will use a robotic rotorcraft to transport various instruments, including a seismometer, to the Shangri-La dune field on Titan. Until then, Titan’s seismic regime can be estimated by simulating wave propagation through assumed subsurface layers using source models. Ridge belts with …

A Broad Iceland Plume Associated With Two Phase Transitions At The 660 Km Discontinuity: Constraints From Receiver Functions, Dan Wang

Doctoral Dissertations

"In spite of the fact that Iceland is frequently regarded as the archetypal example of mantle plumes, the existence, depth extent, origin, dimension and excess temperature of the hypothesized plume remain enigmatic and hotly debated. The controversy mostly originates from the limited vertical resolution of seismic tomography techniques and the associated uncertainty in the depth and lateral extents of the lower wavespeed anomaly. Here we utilize a robust receiver-function-based technique to image the topography of the 410 and 660 km discontinuities bordering the mantle transition zone beneath Iceland and surrounding oceanic regions, and construct thermal and seismic wavespeed models of …

Exploring Dynamic Triggering Of Earthquakes Within The United States & Quaternary Faulting And Urban Seismic Hazards In The El Paso Metropolitan Area, Richard Alexander Alfaro-Diaz

Open Access Theses & Dissertations

Technological advances in combination with the onslaught of data availability allow for large seismic data streams to automatically and systematically be recorded, processed, and stored. Here, we develop an automated approach to identify small, local earthquakes within these large continuous seismic data records. Our aim is to automate the process of detecting small seismic events triggered by a distant large earthquake, recorded at a single station. Specifically, we apply time-domain short-term average (STA) to long-term average (LTA) ratio algorithms to three-component data to create a catalog of detections. We remove some of the false detections by requiring the detection be …

Seismic Structure Of Tanaga Island, Alaska, Kevin F. (Kevin Francis) Lally

WWU Graduate School Collection

Tanaga Island is located in the Central Aleutian Islands and includes four stratovolcanoes: Sajaka, Tanaga, and East Tanaga in the northwest, and Takawangha in the central part of the island. Of these volcanoes, only Tanaga has a record of historical eruptive activity (in 1914). Over 3,000 earthquakes have been recorded beneath the island and the surrounding offshore region since the six-station seismic network was emplaced in 2003. The origin of these earthquakes is not completely understood, and to arrive at this understanding, more accurate hypocenter locations and power spectra need to be determined. A better analyses including improved locations of …

Dense-Array Teleseismic Imaging Of The Southern Albuquerque Basin, Tori S. Finlay

Earth and Planetary Sciences ETDs

The southern Albuquerque basin is a complex area of high extension, multiple orogenies, and ongoing uplift from a midcrustal magma body in which geophysical coverage is sparse. In this thesis, I capitalize on recent innovations in dense-array processing techniques to create virtual source reflection profiles from five teleseismic events during the deployment of the Sevilleta array. The Sevilleta array consisted of ~800 vertical component nodes with ~300 m spacing deployed for 10 days in February of 2015. Virtual source reflection profiles are created by using the free surface of the earth as a virtual seismic source, yielding profiles that mimic …

Application Of Ps Scattering Kernels To Imaging The Mantle Transition Zone With Receiver Functions, Han Zhang, Brandon Schmandt

Earth and Planetary Sciences ETDs

Both the thermal structures and the hydrated level of the mantle transition zone are attractive to researchers in solid Earth science fields. Although some aspects of the questions have been answered based on current geophysical observations, a high resolution seismic map of such layer on a continental scale is still valuable for improving our understanding of the lateral variations inside the mantle transition zone. Here we extend a 3D pre-stacking migration method to make it more applicable for imaging the mantle transition zone depths. After the validation of the method with 1D synthetic data, two types of 2D structures are …

Classifying Microseismicty At Mount St. Helens Using A Large-N Array, Margaret E. Glasgow

Earth and Planetary Sciences ETDs

A dense array of ~1,000 continuously recording, short-period geophones was deployed in the summer of 2014 within ~15 km of Mount St. Helens. Two earthquake catalogs created using reverse time imaging and template detection techniques, increase the detection rate and completeness of the earthquake catalog when compared to the permanent network, Pacific Northwest Seismic Network, catalog. An investigation into event type for ~200 of the earthquake detections leads to the discrimination of two major classification groups, volcano-tectonic and long period. Previous to this study, long period earthquakes had not been identified in the upper crust during a volcanically inactive period …

Seismic Array Studies Of Antarctica And Madagascar, Martin James Pratt

Arts & Sciences Electronic Theses and Dissertations

The scope of this dissertation is broad, involving seismic array studies from Antarctica and Madagascar, and includes aspects of glaciology and oceanography as well as solid Earth geophysics. Chapter 2 focuses on the study of stickslip motion of the Whillans Ice Stream, West Antarctica. It includes methods combining seismic array and GPS time series, from ice stream based-sensors, to determine source dynamics in the framework of an earthquake source. The source characteristics are then analyzed to explain far-field seismic observations of ice stream- sourced surface waves detected throughout West Antarctica. Locations of asperities, or sticky- spots, that cause the Whillans …

Dynamic Triggering In The Coso Geothermal Field, 2004-2013, Richard A. Alfaro-Diaz

Open Access Theses & Dissertations

We take advantage of EarthScope’s USArray Transportable Array (TA), regional seismic networks to investigate 154 M ≥ 7 earthquakes over a ten-year period (2004- 2013), in search of remotely triggered seismicity within the continental United States. We conduct an automated search to detect high frequency signals (which may indicate triggering of small local earthquakes) using a time window of 5 hours before and after each mainshock. The automated detection applies a short-term average (STA) to long-term-average (LTA) algorithms, to create a catalogue of detections. Using the catalog we search for an increase in detection rates after each main-shock. Sharp increases …

Doing More With Short Period Data: Determining Magnitudes From Clipped And Over-Run Seismic Data At Mount St. Helens, John J. Wellik Ii

Dissertations, Master's Theses and Master's Reports - Open

How can we calculate earthquake magnitudes when the signal is clipped and over-run? When a volcano is very active, the seismic record may saturate (i.e., the full amplitude of the signal is not recorded) or be over-run (i.e., the end of one event is covered by the start of a new event). The duration, and sometimes the amplitude, of an earthquake signal are necessary for determining event magnitudes; thus, it may be impossible to calculate earthquake magnitudes when a volcano is very active. This problem is most likely to occur at volcanoes with limited networks of short period seismometers. This …

Effects Of High-Impedance-Contrast Boundary Upon Multi-Modal Seismic Surface Wave Data, Prajwol Tamrakar

UNLV Theses, Dissertations, Professional Papers, and Capstones

Synthetic studies and analyses of an experimental dataset were conducted to address the use of Rayleigh-type surface waves for estimation of shear wave velocity (VS) profiles of shallow bedrock sites. The shallow bedrock presents a high impedance contrast boundary which causes surface wave energy to be partitioned to higher modes. Idealized studies of hypothetical datasets and root-mean-squared calculations of error surfaces showed that if reliable dispersion data are available over a broad frequency spectrum, the VS profile can be recovered using the fundamental mode alone. However, when dispersion data are limited to a relatively narrow frequency band representing what might …

Characterizing The Deformation Of Reservoirs Using Interferometry, Gravity, And Seismic Analyses, Cara Schiek

Open Access Theses & Dissertations

In this Dissertation, I characterize how reservoirs deform using surface and subsurface techniques. The surface technique I employ is radar interferometry, also known as InSAR (Interferometric Synthetic Aperture Radar). The subsurface analyses I explore include gravity modeling and seismic techniques consisting of determining earthquake locations from a small-temporary seismic network of six seismometers. These techniques were used in two different projects to determine how reservoirs deform in the subsurface and how this deformation relates to its remotely sensed surface deformation.

The first project uses InSAR to determine land subsidence in the Mimbres basin near Deming, NM. The land subsidence measurements …