Geophysics and Seismology Commons^™

Integrating Satellite Observations And Modeling Approaches To Study Tectonic And Land Surface Hazards, Jeng Hann Chong

Earth and Planetary Sciences ETDs

The increasing availability of Earth observation satellites, such as SAR and optical platforms, has improved our ability to study the ground deformation processes during, after, and leading up to these natural hazards, such as earthquakes and debris flows. In this dissertation, I analyze satellite geodetic interseismic velocities across the Rakhine-Bangladesh megathrust and the influence of having realistic modeling assumptions for subduction zones to better constrain seismic hazard. I also examined changes in post-fire debris flow likelihood four years after the 2020 Lake Fire in Southern California using a suite of satellite data and field observations. Together, these studies highlight how …

Paleoseismic Evidence Of Directivity For The 1976 Mw 7.5 Motagua Earthquake, Guatemala, Jonathan Obrist-Farner, Jeremy Maurer, Derek Gibson, Trenton Mcenaney, Andreas Eckert, William F. Kenney, Jeffrey Beeson, Nigel Wattrus, Quin Stangeland, Fatima Reyes

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

On 4 February 1976, a Mw 7.5 earthquake along the Motagua fault, Guatemala, ruptured ∼230 km of the North American and Caribbean plate boundary. Today, the plate boundary remains poorly monitored, and the 1976 earthquake is still not fully understood. Here, we present seismic reflection profiles and radiometrically dated sediment core data from six lakes around the Motagua fault, together with reports of destruction and a quasi-dynamic rupture model, which show that the 1976 earthquake experienced strong directivity that impacted the distribution of shaking. The earthquake left behind a detailed record of event deposits (EDs) in five of the six …

Comparative Analysis Of Different Magnetic Anomaly Datasets Using Navigation Performance With Flight Test Data, Aaron P. Nielsen, Brandon M. Blakely, Patrick Duff

Faculty Publications

Magnetic Anomaly Navigation (MagNav) is a map-based method of navigation which relies on accurately obtaining the anomaly field to a high level of precision to achieve good navigation results. This requires utilizing high quality sensors, accurately modeling disturbance fields from the aircraft & other sources, and creating high-fidelity maps. Aeromagnetic survey data or marine track survey data must be processed into a product that can be used as a reference for a magnetic navigator and a variety of techniques can be utilized for this processing. The data collection for different survey types reflects choices typically made to study the underlying …

Mantle Flow And Fault Zone Related Seismic Anisotropy Revealed By A Dense Linear Broadband Array In Southeast Tibet, Jing Wu, Yinshuang Ai, Stephen S. Gao, Peixi Huang, Fansheng Kong, Deke Xu, Jianguo Song, Xinyu Gao, Mengyi Wei, Long Li, Jien Zhang, Yanbin Zhang, Yingying Zhang

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Southeast Tibet, a key region for the southeastward extrusion of the Tibetan Plateau, remains debated in terms of its tectonic deformation in response to the ongoing collision between the Indian and Eurasian plates. In this study, we applied shear-wave splitting analysis of core-refracted phases recorded by a newly deployed dense seismic array and six permanent stations to delineate crustal and mantle deformation processes. The observed fast polarization directions are predominantly aligned NNW–SSE, while the splitting delay times vary across four sub-blocks. The anisotropy pattern suggests a dominantly asthenospheric origin, consistent with southeastward-directed mantle flow associated with the extrusion of the …

New Precipitation Is Scarce In Deep Soils: Findings From 47 Forest Plots Spanning Switzerland, Emily I. Burt, Scott T. Allen, Sabine Braun, Simon Tresch, James W. Kirchner, Gregory R. Goldsmith

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

As precipitation infiltrates into soils, it can recharge them, displace previously stored waters, or bypass already-filled pores. Using 3,697 δ2H and δ18O measurements of water collected nearly monthly over >3 years in 47 forest plots across Switzerland, we present a systematic investigation of the controls on mobile soil water transport. We quantified the lags and damping of water as it percolates downward using young water fraction analysis (Fyw), and the fractions of soil water composed by precipitation that fell within the previous month (new water fractions, Fnew). The Fnew of water sampled in surface soils ranged …

Receiver Function Imaging Of The Mantle Transition Zone Beneath The East Sayan Mountains And Adjacent Area In Central Asia: Implications For Lithospheric Drip And Intraplate Cenozoic Volcanism, Yangyang Liao, Kelly H. Liu, Stephen S. Gao

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

To provide constraints on the formation mechanisms of intracontinental volcanisms and intriguing lithospheric thickness variations in the East Sayan Mountains and surrounding areas, we stack P-to-s receiver functions to image the 410-km and 660-km discontinuities. Mantle transition zone (MTZ) thickening observed in a continuous area is attributable to ancient slab remnants, and Cenozoic volcanisms in the peripheral area can be explained by slab dehydration. The thinning of the MTZ in the Tuva-Mongolian Massif can be explained by mantle upwelling branches induced by slab subduction. Our results reveal an approximately circular area in the MTZ that is significantly thicker than usual, …

The Compositional And Dynamical Properties Of Exoplanets, Cody James Shakespeare

UNLV Theses, Dissertations, Professional Papers, and Capstones

The solid surface density profile of protoplanetary discs, and the composition of these solids, can be formed through sequential condensation models of dust precipitating from the cooling gas of the solar nebula. I continue developing a code that reproduces the chemical compositions of most chondrites as well as the bulk compositions of the rocky planets using our partial condensation model with an evolving disc. I extend this validated code to exoplanet systems with different initial elemental ratios, like the carbon-to-oxygen ratio and estimated stellar abundances over the age of the universe. I have improved this dust condensation code to include …

Mantle Flow And Crustal Deformation Revealed By Seismic Anisotropy In The Subduction Zone Beneath Myanmar, Enbo Fan, Mingming Jiang, Yinshuang Ai, Stephen S. Gao, Kelly H. Liu, Yumei He, Yiming Bai, Guangbing Hou, Yuan Ling, Chit Thet Mon, Myo Thant, Kyaing Sein

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The oblique convergence of the Indian and Eurasian plates drives significant deformation in the crust and mantle beneath Myanmar. However, the crustal deformation in the Indo-Burman Ranges (IBR) and mantle flow beneath Myanmar and adjacent areas remain unclear due to limited studies. We utilized data from the newly deployed second phase of the China-Myanmar Geophysical Survey of the Myanmar Orogen array to perform shear wave splitting analysis of PKS, SKKS, and SKS (XKS) phases. Our results, together with previous findings, provide new insights into mantle flow and crustal deformation across central Myanmar. In the IBR, we observed a transition from …

Mapping Sedimentary And Crustal Thicknesses In The Northern Atlantic Ocean From Public Domain Geophysical Data, Hermione Lofton

College of Arts and Sciences: Undergraduate Theses and Other Student Projects

The Northern Atlantic Ocean is a complex region that contains many inactive and active tectonic features. These features include the Jan Mayen Microcontinent, Jan Mayen Fracture Zone, Aegir Ridge, Kolbeinsey Ridge, the Greenland-Iceland-Faroe Ridge, the Voring Plateau, the Voring Spur, and the Iceland Hotspot. This project is motivated by the region’s complex geology and its highly debated tectonic history and disputed crustal affinity. This study aims to evaluate tectonic elements of the Northern Atlantic Ocean with three major objectives. The first objective is to develop a map of crustal thickness from publicly available seismic refraction data. For the second objective, …

High-Frequency Seismic Noise In Desert Environments, Alexis Hernandez

Open Access Theses & Dissertations

This study investigates the generation and modulation of ambient seismic noise in arid environments, with a focus on aeolian processes such as saltation, wind shear, and precipitation events. Using a dense array of three-component seismic nodes co-located with meteorological sensors and a novel particle transport instrument (SANTRI), high-frequency seismic signatures were examined within the Jornada Experimental Range in southern New Mexico. Time-frequency analysis reveals that wind-driven saltation events produce measurable seismic energy enhancements, particularly within the 100-300 Hz band, with clear spectral distinctions between wind-only forcing and particle-laden transport. Additionally, rainfall events were identified by elevated seismic amplitudes in the …

Deformation And Earthquake Potential On The North America - Caribbean - Cocos Triple Junction In Guatemala, Jeremy Maurer, Andreas Eckert, Qiaoqi Sun, Jonathan Obrist-Farner

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The triple junction between the Cocos (CO), North American (NA), and Caribbean (CA) tectonic plates in Guatemala is a region of high seismic risk and includes many large faults and historic earthquakes. Previous analyses of the tectonic system have been overly simplified, resulting in discrepancies between geologically derived and geodetic models of fault slip rate. This study leverages available geodetic, seismic, and geologic data to develop new strain rate maps and faulting models for the region. We find that locking on the regional faults matches historic reports of large earthquakes and that multiple minor fault segments are active and accommodate …

Magnetic Reconnection In Space: From Two-Dimensional Magnetohydrodynamic (Mhd) Simulations To Three-Dimensional Particle-In-Cell (Pic) Simulations, Shan-Chang Lin

Dartmouth College Ph.D Dissertations

Magnetic reconnection is a physical process in plasmas that converts magnetic energy into plasma kinetic energy and thermal energy. It plays an important role in the generation of solar flares, interactions between the solar wind and Earth's magnetosphere, and magnetic confinement fusion devices. This thesis focuses on studying magnetic reconnection using computational methods, including two-dimensional (2D) magnetohydrodynamics (MHD) simulations to study Petschek-type reconnection, estimating the timescale from a thin current sheet to fully developed reconnection using 2D particle-in-cell (PIC) simulations, and magnetic reconnection X-line spreading in the current direction using three-dimensional (3D) PIC simulations.

This thesis contributes to the understanding …

Leveraging Weekly Snow Cover Time Series For Improved Glacier Monitoring And Modeling, Rainey Aberle, Ellyn M. Enderlin, David R. Rounce, Shad O'Neel, Brandon Tober, Alexandra Friel

Boise State University Publications and Presentations

Seasonal snow and ice melt strongly influence glacier mass balance, yet sparse sub-annual observations limit our understanding of seasonal dynamics. Here we construct and analyze weekly snow cover time series for 200 glaciers across western North America from 2013 to 2023 using an automated image processing pipeline. Snow cover varied widely across the region: snow minima timing varied with latitude — from August from 62 to 64N to October from 48 to 50N—and accumulation area ratios ranged from near-zero to 0.92 (median of 0.52). A comparison of snowlines from observations and the PyGEM glacier mass balance model revealed seasonally evolving …

Seeking Structure In Complex Systems: From Feature Analysis To Space-Time Causal Discovery With Earth Science Applications, Jeffrey J. Nichol

Computer Science ETDs

Complex systems are difficult to study because of their many interacting parts, emergent phenomena, and feedback loops. These systems underpin all life on Earth. We need improved tools for seeking an understanding of them. This body of research presents my investigations into data-driven methods for understanding complex systems, including my invention of a novel causal discovery meta-algorithm for space-time gridded data. I demonstrated machine learning feature importance and causal discovery capabilities for comparing simulated and observed climate data. I developed a new benchmark for modeling space-time dynamics of locally driven phenomena and examined a prominent causal discovery algorithm. Finding that …

Retraction: A Database Of Teleseismic Shear-Wave Splitting Measurements For The Ordos Block And Adjacent Areas(Seismological Research Letters (2022), 93, 5, (2731–2739), 10.1785/0220210310), Lin Liu, Stephen S. Gao, Kelly H. Liu, Tu Xue, Yan Jia, Sanzhong Li

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

An earlier version of this article (Liu et al., 2022) included private data from the Himalayan-III program which should not have been made public. The authors acknowledge and regret their negligence during the selection of the measurements. The impacted data represent only 2.7% of the total data published in this article, and after review, the authors and the editors agree that this unintentional error has no bearing on the work's scientific conclusions. Therefore, we are retracting the impacted data and have made corrections to remove any Himalayan-III program data from the article's text, figures, and supplemental tables.

The Surface Water And Ocean Topography (Swot) Mission For River And Lake Ice Application, Sunwoo Yoon

Earth Sciences Theses and Dissertations

The Surface Water and Ocean Topography (SWOT) mission, launched in December 2022, is designed for global survey of Earth’s surface water. However, the seasonal freezing of lakes and rivers combined with SWOT’s unique interferometric radar characteristics presents a valuable opportunity to assess its potential for river and lake ice applications. In this dissertation, I first compare backscatter characteristics over open water and frozen lakes and rivers. I demonstrate strong contrast in backscatter between water and ice while accounting for incidence angle, highlighting SWOT’s capability to discriminate between surface cover types. However, overlapping backscatter signatures suggest further investigation of drivers of …

Deciphering A Quantitative Relationship Between Rifting And Crustal Melt Fraction: Insights From The Incipient Okavango Rift Zone, Tuo Wang, Ling Chen, Stephen S. Gao, Kelly H. Liu

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Rifting and magmatism are fundamental geological processes in the evolution of the lithosphere; however, quantitative investigations of their relationship are rare. The Okavango Rift Zone (ORZ) is in the early stages of rifting and magmatic activity and thus is an ideal locale to study this relationship. We examine the relationship using two primary crustal structure parameters: crustal thickness and average Vp/Vs ratio obtained from receiver functions. Our large Vp/Vs estimates indicate the existence of melts within the crust of the ORZ. Comparing our results with those of other continental rifts, we identify a quantitative relationship between rifting and crustal melt …

Characterization Of The Quaternary Active Twin Lakes Fault, Mount Hood, Oregon, Johnathan Peterson

University Honors Theses

The High Cascades chain of volcanoes results from Cascade Arc volcanism and is responsible for the generation of the highest topography in the state of Oregon. Surrounding Mt. Hood at the crest of the Cascade chain in northern Oregon is the Mt. Hood Fault Zone, an extensional fault zone of generally north-south trending normal faults that down-drop this high volcanic topography. The Twin Lakes Fault is located just south of Mt. Hood and is one of the southernmost faults in the Mt. Hood Fault Zone, previously mapped as approximately 12-13 km in length. This study provides the first in-depth characterization …

Calculating Moment Magnitude Using The Coda Calibration Technique To Update The Earthquake Catalog Of Iraq (1900-2021), Muntadher Al-Kaabi

Theses and Dissertations

The first comprehensive earthquake catalog for Iraq based on moment magnitude (Mw) ‎was compiled by Onur et al. (2017). It spanned the period from 1900 until the end of ‎‎2009, covered the region between 26°–40° N latitudes and 36°–51° E longitudes, and ‎included more than 18,000 earthquakes, of which roughly 4,000 are of Mw 4.0 or larger. ‎With the ongoing efforts of updating the probabilistic seismic hazard assessment ‎‎(PSHA) and the Iraqi building code, the need for an updated earthquake catalog for Iraq ‎in terms of moment magnitude (Mw) has been raised. Robust estimation of moment ‎magnitude (Mw) can be …

Seismological Applications To Crustal Deformation And Explosion Discrimination, Olumide Adedeji

Earth and Planetary Sciences ETDs

There are many outstanding questions in seismology and plate tectonics that remain unresolved due to the complexity of seismic wave propagation, fault system evolution, and sedimentary-tectonic interactions. In this dissertation, I analyze seismic and acoustic data to improve event discrimination, understand strain partitioning along a transpressive plate boundary, and investigate the influence of tectonic deformation on sedimentary processes. Using seismic arrays, I assess the detectability of Ground Coupled Airwaves (GCA) generated by shallow borehole explosions and earthquakes, demonstrating that GCA detections are highly dependent on source type, environmental conditions and sensor distribution. Along the Queen Charlotte Plate Boundary, I analyze …