Physical Sciences and Mathematics Commons^™

Rhizobium Symbiotic Capacity Shapes Root-Associated Microbiomes In Soybean, Yuanhui Lu, Bin Ma, Wenfeng Chen, Klaus Schlaeppi, Matthias Erb, Erinne Stirling, Lingfei Hu, Entao Wang, Yunzeng Zhang, Kankan Zhao, Zhijiang Lu, Shudi Ye, Jianming Xu

Environmental Science and Geology Faculty Research Publications

Root-microbiome interactions are of central importance for plant performance and yield. A distinctive feature of legumes is that they engage in symbiosis with N₂-fixing rhizobia. If and how the rhizobial symbiotic capacity modulates root-associated microbiomes are still not yet well understood. We determined root-associated microbiomes of soybean inoculated with wild type (WT) or a noeI mutant of Bradyrhizobium diazoefficiens USDA 110 by amplicon sequencing. UPLC-MS/MS was used to analyze root exudates. The noeI gene is responsible for fucose-methylation of Nod factor secreted by USDA 110 WT strain. Soybean roots inoculated with the noeI mutant showed a significant decrease …

Combination Of High Specific Activity Carbon-14 Labeling And High Resolution Mass Spectrometry To Study Pesticide Metabolism In Crops: Metabolism Of Cycloxaprid In Rice, Dahang Shen, Zhijiang Lu, Jiayin Zhong, Sufen Zhang, Qingfu Ye, Wei Wang, Jay Gan

Environmental Science and Geology Faculty Research Publications

The study of pesticide metabolism in crops is critical for assessing the mode of action and environmental risks of pesticides. However, the study of pesticide metabolism in crops is usually complicated and it is often a daunting challenge to accurately screen the metabolites of novel pesticides in complex matrices. This study demonstrated a combined use of high-specific activity carbon-14 labeling and high-resolution mass spectrometry (HSA-¹⁴C-HRMS) for metabolism profiling of a novel neonicotinoid cycloxaprid in rice. By generating the characteristic radioactive peaks on the liquid chromatogram, the use of ¹⁴C can eliminate the severe interference of complex matrices …

Novel Application Of 210po-210pb Disequilibria To Date Snow, Melt Pond, Ice Core, And Ice-Rafted Sediments In The Arctic Ocean, Mark Baskaran, Katherine Krupp, Mark Baskaran

Environmental Science and Geology Faculty Research Publications

We collected surface ocean water, snow, grab ice, ice core, melt pond and ice-rafted sediment (IRS) from 5 ice stations during the Western Arctic US GEOTRACES cruise (USGCG Healy; August 10 – October 7, 2015) and analyzed for 210Po (T1/2 = 138.4 days) and 210Pb (T1/2 = 22.3 years) in dissolved and particulate phases (snow, grab ice, ice core, surface seawater) to investigate the 210Po:210Pb disequilibria in these matrices. Thirteen aerosol samples, using a large-volume aerosol sampler (PM10), from Dutch Harbor, AK to North Pole, were also collected and analyzed for 210Po/210Pb to quantify the atmospheric depositional input to the …

210po And 210pb As Tracers Of Particle Cycling And Export In The Western Arctic Ocean, Wokil Bam, Kanchan Maiti

Environmental Science and Geology Faculty Research Publications

The distribution and vertical fluxes of particulate organic carbon and other key elements in the Arctic Ocean are primarily governed by the spatial and seasonal changes in primary productivity, areal extent of ice cover, and lateral exchange between the shelves and interior basins. The Arctic Ocean has undergone rapid increase in primary productivity and drastic decrease in the areal extent of seasonal sea ice in the last two decades. These changes can greatly influence the biological pump as well as associated carbon export and key element fluxes. Here, we report the export of particulate organic and inorganic carbon, particulate nitrogen …

A Global Dataset Of Atmospheric 7be And 210pb Measurements: Annual Air Concentration And Depositional Flux, Fule Zhang, Jinlong Wang, Mark Baskaran, Qiangqiang Zhong, Yali Wang, Jussi Paatero, Jinzhou Du

Environmental Science and Geology Faculty Research Publications

7Be and 210Pb air concentration and depositional flux data provide key information on the origins and movements of air masses, as well as atmospheric deposition processes and residence time of aerosols. After their deposition onto the Earth's surface, they are utilized for tracing soil redistribution processes on land, particle dynamics in aquatic systems, and mixing processes in open ocean. Here we present a global dataset of air concentration and depositional flux measurements of atmospheric 7Be and 210Pb made by a large number of global research communities. Data were collected from published papers between 1955 and early 2020. It includes the …

Biis: The Last British Ice Sheet, A Review Of The Most Recent Major Glaciation Of Great Britain And Ireland, Benediktas Gaskevicius

Honors College Theses

The British Irish Ice Sheet was a substantial ice mass covering the British Isles during the most recent glaciation that ended around 11,700 years ago. Oftentimes referred to as the BIIS, it is subdivided into two sections, a western and eastern side that covered Great Britain and Ireland, with the Irish basin in the middle. Some notable areas of study around Great Britain and Ireland include the ’Bizzle’ in Northern England, which was transformed by the effects of the eastern margin of the BIIS, the Carstair Kames in Scotland, a locality known internationally for its esker system, The Minch region …

Bayesian Seismic Refraction Inversion For Critical Zone Science And Near-Surface Applications, Mong-Han Huang, Berit Hudson-Rasmussen, Scott Burdick, Vedran Lekić, Mariel D. Nelson, Kristen E. Fauria, Nicholas Schmerr

Environmental Science and Geology Faculty Research Publications

The critical zone (CZ) is the region of the Earth’s surface that extends from the bottom of the weathered bedrock to the tree canopy and is important because of its ability to store water and support ecosystems. A growing number of studies use active source shallow seismic refraction to explore and define the size and structure of the CZ across landscapes. However, measurement uncertainty and model resolution at depth are generally not evaluated, which makes the identification and interpretation of CZ features inconclusive. To reliably resolve seismic velocity with depth, we implement a Transdimensional Hierarchical Bayesian (THB) framework with reversible-jump …

Integrated Borehole, Radar, And Seismic Velocity Analysis Reveals Dynamic Spatial Variations Within A Firn Aquifer In Southeast Greenland, S. F. Killingbeck, N. C. Schmerr, L. N. Montgomery, A. D. Booth, P. W. Livermore, J. Guandique, O. L. Miller, S. Burdick, R. R. Forster, L. S. Koenig, A. Legchenko, S. R. M. Ligtenberg, C. Miège, D. K. Solomon, L. J. West

Environmental Science and Geology Faculty Research Publications

Perennial water storage in firn aquifers has been observed within the lower percolation zone of the southeast Greenland ice sheet. Spatially distributed seismic and radar observations, made ~50 km upstream of the Helheim Glacier terminus, reveal spatial variations of seismic velocity within a firn aquifer. From 1.65 to 1.8 km elevation, shear-wave velocity (Vs) is 1,290 ± 180 m/s in the unsaturated firn, decreasing below the water table (~15 m depth) to 1,130 ± 250 m/s. Below 1.65 km elevation, Vs in the saturated firn is 1,270 ± 220 m/s. The compressional-to-shear velocity ratio decreases in the downstream saturated zone, …

Direct P-Wave Anisotropy Measurements At Homestake Mine: Implications For Wave Propagation In Continental Crust, James Atterholt, Sarah J. Brownlee, Gary L. Pavlis

Environmental Science and Geology Faculty Research Publications

We measured anisotropic seismic properties of schists of the Homestake Formation located at a depth of 1478 m in the Sanford Underground Research Facility (SURF) in the Black Hills of South Dakota, USA. We deployed a 24-element linear array of three-component geophones in an area in the Homestake Mine called 19-ledge. An airless jackhammer source was used to shoot two profiles: (1) a walkaway survey to appraise any distance dependence and (2) a fan shot profile to measure variations with azimuth. Slowness estimates from the fan shot profile show a statistically significant deviation with azimuth with the expected 180° variation …

A Framework For Aquatic Invasive Species Surveillance Site Selection And Prioritization In The Us Waters Of The Laurentian Great Lakes, Andrew J. Tucker, W. Lindsay Chadderton, Gust Annis, Alisha D. Davidson, Joel Hoffman, Jon Bossenbroek, Stephen Hensler, Michael Hoff, Erika Jensen, Donna R. Kashian, Sarah Lesage, Timothy Strakosh

Environmental Science and Geology Faculty Research Publications

Risk-based prioritization for early detection monitoring is of utmost importance to prevent and mitigate invasive species impacts and is especially needed for large ecosystems where management resources are not sufficient to survey all locations susceptible to invasion. In this paper we describe a spatially-explicit and quantitative approach for identifying the highest risk sites for aquatic invasive species (AIS) introduction into the United States’ waters of the Laurentian Great Lakes, a vast inland sea with a surface area of 246,049 square km and a shoreline length of 16,431 km. We compiled data from geospatial metrics available across all of the US …

Understanding The Bioavailability Of Pyrethroids In The Aquatic Environment Using Chemical Approaches, Zhijiang Lu, Jay Gan, Xinyi Cui, Laura Delgado-Moreno, Kunde Lin

Environmental Science and Geology Faculty Research Publications

Pyrethroids are a class of commonly used insecticides and are ubiquitous in the aquatic environment in various regions. Aquatic toxicity of pyrethroids was often overestimated when using conventional bulk chemical concentrations because of their strong hydrophobicity. Over the last two decades, bioavailability has been recognized and applied to refine the assessment of ecotoxicological effects of pyrethroids. This review focuses on recent advances in the bioavailability of pyrethroids, specifically in the aquatic environment. We summarize the development of passive sampling and Tenax extraction methods for assessing the bioavailability of pyrethroids. Factors affecting the bioavailability of pyrethroids, including physicochemical properties of pyrethroids, …

Evaluation Of An Educational Campaign To Improve The Conscious Consumption Of Recreationally Caught Fish, Corey A. Krabbenhoft, Susan Manente, Donna R. Kashian

Environmental Science and Geology Faculty Research Publications

Consumption guidelines are a common way of improving conscious consumption behaviors in areas where game fish are known to contain contaminants. However, guideline information can be difficult to distribute, and effectiveness difficult to measure. To increase the distribution and effectiveness of guideline information for the Detroit River, an educational campaign was launched in 2010, which included distribution of pamphlets with consumption information, posting of permanent signs at popular fishing locations, and hiring River Walkers to personally communicate with anglers. In 2013 and 2015, we conducted in-person surveys of active shoreline anglers to determine the effectiveness of education and outreach efforts. …

Iron Fertilization With Enhanced Phytoplankton Productivity Under Minimal Sulfur Compounds And Grazing Control Analysis In Hnlc Region, Tai-Jin Kim, G. H. Hong, D. G. Kim Kim, Mark Baskaran

Environmental Science and Geology Faculty Research Publications

The present study investigated quantitatively the significance of HNLC (high-nutrient low-chlorophyll) regions and its grazing control with the im- proved iron fertilization for climate change. The limitation of iron (Fe) for phytoplankton growth in HNLC regions was confirmed by sulfur compounds (S) such as volcanic ash and hydrogen sulfide (H2S) in batch cultures, whose chemical sediment of Fe3S4 showed 4.06 wt%. The technologies developed for iron fertilization since 1993 till now were not practical to provide sufficient amounts of bioavailable iron due to sedimentary iron sulfides induced by undersea volcanic sulfur compounds. The proposed technology for iron fertilization was improved …

Flux Of Particulate Elements In The North Atlantic Ocean Constrained By Multiple Radionuclides, Christopher T. Hayes, Erin E. Black, Robert F. Anderson, Mark Baskaran, Ken O. Buesseler, Matthew A. Charette, Hai Cheng, J. Kirk Cochran, R. Lawrence Edwards, Patrick Fitzgerald, Phoebe J. Lam, Yanbin Lu, Stephanie O. Morris, Daniel C. Ohnemus, Frank J. Pavia, Gillian Stewart, Yi Tang

Environmental Science and Geology Faculty Research Publications

Sinking particles strongly regulate the distribution of reactive chemical substances in the ocean, including particulate organic carbon and other elements (e.g., P, Cd, Mn, Cu, Co, Fe, Al, and 232Th). Yet, the sinking fluxes of trace elements have not been well described in the global ocean. The U.S. GEOTRACES campaign in the North Atlantic (GA03) offers the first data set in which the sinking flux of carbon and trace elements can be derived using four different radionuclide pairs (238U:234Th ;210Pb:210Po; 228Ra:228Th; and 234U:230Th) at stations co-located with sediment trap fluxes for comparison. Particulate organic carbon, particulate P, and particulate Cd …

Fingerprinting Sediment Transport In River-Dominated Margins Using Combined Mineral Magnetic And Radionuclide Methods, Jinlong Wang, Weigou Zhang, M. Baskaran, Jinzhou Du, Feng Zhou, Hui Wu

Environmental Science and Geology Faculty Research Publications

Both magnetic properties and radionuclides are widely used to trace sediment transport in aquatic environments; however, these methods have not been used in combination. In this study, the East China Sea (ECS), a typical river-dominated margin, was chosen to demonstrate the advantages of combining these two methods to track sediment movements on a seasonal to annual timescale. The ratios between saturation isothermal remnant magnetization and anhysteretic remnant magnetization (χARM/SIRM) and 7Be/210Pbex activity ratios as well as mass balance of 7Be provide information on the seasonal transport of sediment from the Changjiang Estuary to the neighboring shelf. Both 210Pb budget and …

Shear Wave Tomography Beneath The United States Using A Joint Inversion Of Surface And Body Waves, E. M. Golos, H. Fang, H. Yao, H. Zhang, Scott Burdick, F. Vernon, A. Schaeffer, S. Lebedev, R. D. Van Der Hilst

Environmental Science and Geology Faculty Research Publications

Resolving both crustal and shallow-mantle heterogeneity, which is needed to study processes in and fluxes between crust and mantle, is still a challenge for seismic tomography. Body wave data can constrain deep features but often produce vertical smearing in the crust and upper mantle; in contrast, surface wave data can provide good vertical resolution of lithospheric structure but may lack lateral resolution and are less sensitive to the deeper Earth. These two data types are usually treated and inverted separately, and tomographic models therefore do not, in general, benefit from the complementary nature of sampling by body and surface waves. …

Cyanobacteria Reduce Quagga Mussel (Dreissena Rostriformis Bugensis) Spawning And Fertilization Success, Anna G. Boegehold, Nicholas S. Johnson, Jeffrey L. Ram, Donna R. Kashian

Environmental Science and Geology Faculty Research Publications

Quagga mussels (Dreissena rostriformis bugensis) are highly fecund broadcast spawners invasive to freshwaters of North America and western Europe. We hypothesized that environmental cues from phytoplankton can trigger gamete release in quagga mussels. Nutritious algae may stimulate dreissenid spawning, but less palatable food, such as bloom-forming cyanobacteria, could be a hindrance. The objective of our study was to test whether exposure to cyanobacteria can inhibit quagga mussel spawning and fertilization. We assessed spawning in the presence of serotonin, a known spawning inducer, where adult quagga mussels placed in individual vials were exposed to 13 cyanobacteria cultures and purified algal toxin …

Characteristics Of Deep Crustal Seismic Anisotropy From A Compilation Of Rock Elasticity Tensors And Their Expression In Receiver Functions, Sarah J. Brownlee, Vera Schulte-Pelkum, Anissha Raju, Kevin Mahan, Cailey Condit, Omero Felipe Orlandini

Environmental Science and Geology Faculty Research Publications

Rocks in the continental crust are long lived and have the potential to record a wide span of tectonic history in rock fabric. Mapping rock fabric in situ at depth requires the application of seismic methods. Below depths of microcrack closure seismic anisotropy presumably reflects the shape and crystallographic preferred orientations influenced by deformation processes. Interpretation of seismic observables relevant for anisotropy requires assumptions on the symmetry and orientation of the bulk elastic tensor. We compare commonly made assumptions against a compilation of 95 bulk elastic tensors from laboratory measurements, including electron backscatter diffraction and ultrasound, on crustal rocks. The …

Investigations Of The Spatial And Temporal Variations Of Sr And Nd Isotopes In Sediments From Two Indian Rivers: Implications To Source Identification, Sonali Pradhan, Jing Zhang, Mark Baskaran, Prabhaker Vasant Shirodkar, Ying Wu, Umesh Kumar Pradhan

Environmental Science and Geology Faculty Research Publications

Radiogenic isotopes of Sr and Nd provide crucial information on chemical and physical erosion processes, therefore used as tracers for fingerprinting the sources of fluvial sediments. Moreover, elemental geochemistry, 87Sr/86Sr and 143Nd/144Nd signatures in silicate fractions of sediments primarily reflect intricate controls of characteristics and provenance of sediment. A suite of sediment samples collected from two rivers of India, Narmada (large) and Netravati (small) were analyzed for elemental concentrations, 87Sr/86Sr and 143Nd/144Nd in silicate as well as acid-leachable fractions. 87Sr/86Sr in acid-leachable sediment fractions from both the rivers (0.7094 ± 0.0002 for Narmada and 0.7158 ± 0.003 for Netravati) showed …

Velocity Variations And Uncertainty From Transdimensional P-Wave Tomography Of North America, Scott Burdick, Vedran Lekić

Environmental Science and Geology Faculty Research Publications

High-resolution models of seismic velocity variations constructed using body-wave tomography inform the study of the origin, fate and thermochemical state of mantle domains. In order to reliably relate these variations to material properties including temperature, composition and volatile content, we must accurately retrieve both the patterns and amplitudes of variations and quantify the uncertainty associated with the estimates of each. For these reasons, we image the mantle beneath North America with P-wave traveltimes from USArray using a novel method for 3-D probabilistic body-wave tomography. The method uses a Transdimensional Hierarchical Bayesian framework with a reversible-jump Markov Chain Monte Carlo algorithm …

Investigation Of Firn Aquifer Structure In Southeastern Greenland Using Active Source Seismology, Lynn N. Montgomery, Nicholas Schmerr, Scott Burdick, Richard R. Forster, Lora Koenig, Anatoly Legchenko, Stefan Ligtenberg, Clément Miège, Olivia L. Miller, D. Kip Solomon

Environmental Science and Geology Faculty Research Publications

In spring of 2011, a perennial storage of water was observed in the firn of the southeastern Greenland Ice Sheet (GrIS), a region of both high snow accumulation and high melt. This aquifer is created through percolation of surface meltwater downward through the firn, saturating the pore space above the ice-firn transition. The aquifer may play a significant role in sea level rise through storage or draining freshwater into the ocean. We carried out a series of active source seismic experiments using continuously refracted P-waves and inverted the first P-arrivals using a transdimensional Bayesian approach where the depth, velocity, and …

Memorium: Bhamidipati Lakshmidhara Kanakadri Somayajulu (1937-2016), Mark Baskaran, R. Ramesh

Environmental Science and Geology Faculty Research Publications

The demise of B. L. K. Somayajulu, an illustrious nuclear geochemist, brings great sadness to the community of geo- logists, geochemists and oceanographers in India and elsewhere.

Seismic Anisotropy As A Function Of Mineralogy And Rock Type In Chester Gneiss Dome, Southeast Vermont, Brittany Watling

Wayne State University Theses

Our knowledge of composition and structure in middle and lower crustal rocks is limited due to restricted accessibility, and thus comes mainly from studies of seismic velocities. But isotropic seismic velocities are not sufficient to distinguish between the many possible rock types in the middle and lower crust. Seismic anisotropy is the directional dependence of seismic velocity, and may provide further constraints on mineralogy and rock type. This study is focused on characterizing the seismic anisotropy of rocks from the Chester dome in southeast Vermont. We have simplified the Chester dome rock types into four groups based on rock type …

Integration Of Deterministic And Stochastic Models In A 1,4-Dioxane Contaminated Glacial Aquifer System, Washtenaw County, Michigan, Lena Kristin Pappas

Wayne State University Theses

Hybrid models incorporating stochastic variability within a deterministic hydrostratigraphic framework provide an effective way to assess uncertainty in flow and transport model predictions. This study evaluated the distribution of groundwater flow and contaminant transport pathways in two ensembles of spatially variable hydraulic conductivity (K) distributions. The models comprised a 360 ft-thick sequence of Pleistocene glacial sediments in in an approximately 8 mi2 area across Washtenaw County, Michigan. Conditioned K fields were generated using Sequential Gaussian Simulation (SGS) and Sequential Indicator Simulation (SIS) constructed using indicator classes based on natural gamma ray logs from 77 monitoring wells. K fields were modeled …

Portable X-Ray Fluorescence Measurement Viability In Organic Rich Soils: Pxrf Response As A Function Of Organic Matter Presence, Roozbeh Ravansari

Wayne State University Theses

Portable X-Ray fluorescence provides a cost effective method for producing rapid geochemical data. With advancements in X-Ray generation and detection technology, pXRF has become feasible for use on pedologic materials. Factors affecting pXRF soil measurements such as heterogeneity, moisture content, object geometry, and matrix interferences are widely recognized. However, the influence of organic matter on pXRF soil measurements is poorly understood.

This study examined the influence of organic matter fraction on pXRF trace metal measurements in a soil matrix. Incremental addition of three organic matter surrogates (cellulose, graphite powder, and confectioner’s sugar) was used to investigate the influence of increasing …

Effects Of Folding On Mineral Cpos In Gneiss: Implications For Lower Crustal Seismic Anisotropy, Alexia K. Sarnowsky

Wayne State University Theses

Isotropic seismic properties are not sufficient to distinguish between many rock types believed to make up the middle and lower continental crust. Seismic anisotropy is the directional dependence of seismic velocity, which we can use to improve our understanding of the composition and structure of the middle and lower continental crust. Our rationale is that seismic anisotropy in the middle and lower crust is controlled by the crystallographic preferred orientation (CPO) of minerals. The effects of folding on mineral CPO in a folded gneiss from the Coweeta Group in North Carolina is used for this study, and we should be …

Modeling Bedrock Transmissivity; Implications For Contaminant Transport In An Overlying Glacial Aquifer System, Amanda Pruehs

Wayne State University Theses

This study evaluated alternative representations of bedrock surface and bedrock transmissivity on advective transport predictions in an 11 km x 15 km x 116 m groundwater model. Bedrock topography, initially based on a map by Kunkle (1961), was reinterpreted using data from 227 additional bedrock penetrations drilled in the last 55 years. Varying assumptions of hydraulic conductivity were employed to model a range of bedrock conductivity from 1 to 3 orders of magnitude less than the overlying glacial aquifer system. MODPATH forward particle tracking and MT3DMS advective-dispersive transport modeling were employed to explore the influence of bedrock configuration and conductivity …

Mobile Mud Dynamics In The East China Sea Elucidated Using 210pb, 137cs, 7be, And 234th As Tracers, Jinlong Wang, Jinzhou Du, Mark Baskaran, Jing Zhang

Environmental Science and Geology Faculty Research Publications

“Mobile mud” (MM), which has fine grain size distribution (>90% clay + silt, and <5% sand) and high porosity (≥0.50), plays an important role in the biogeochemical cycles in the estuarine areas and the inshore shelf. A suite of MM samples from the coastal area of the East China Sea (ECS) was collected in spring and summer of 2011 to observe their spatial and temporal distribution, grain size, and radionuclides concentrations. The MM thickness ranged from 0.5 to 11 cm (average: 2.2 cm (May) and 3.9 cm (August)). The thick mud layer is mainly distributed along the coast, with an area of 2.2 × 104 km2 in May and 1.5 × 104 km2 in August, with corresponding masses of 8.8 × 108 and 7.8 × 108 t, respectively. The estimated masses of MM are considerably larger than the annual sediment discharge mass of the Changjiang River. The distribution of 137Cs inventories in MM indicates that 137Cs can be effectively utilized as a transport tracer of MM in the river‐dominated estuaries and coastal areas. The higher inventories of 7Be in MM in the river mouth in spring are attributed to higher depositional flux and higher sediment discharge. The ratio of the MM inventory of 234Thex/production in the overlying water column of >2.5 in south inshore indicates that the sediment focusing resulted in the increased mass flux. The residence time of MM is estimated as 3–6 years both by mass balance of MM and 210Pbex in MM.

Understanding Acceptable Level Of Risk: Incorporating The Economic Cost Of Under-Managing Invasive Species, Alisha D. Davidson, Chad L. Hewitt, Donna R. Kashian

Environmental Science and Geology Faculty Research Publications

Management of nonindigenous species includes prevention, early detection and rapid response and control. Early detection and rapid response depend on prioritizing and monitoring sites at risk for arrival or secondary spread of nonindigenous species. Such monitoring efforts require sufficient biosecurity budgets to be effective and meet management or policy directives for reduced risk of introduction. Such consideration of risk reduction is rarely considered, however. Here, we review the concepts of acceptable level of risk (ALOR) and associated costs with respect to nonindigenous species and present a framework for aligning risk reduction priorities with available biosecurity resources. We conclude that available …

Inferring The Oriented Elastic Tensor From Surface Wave Observations: Preliminary Application Across The Western United States, Jiayi Xie, Michael H. Ritzwoller, S. J. Brownlee, B. R. Hacker

Environmental Science and Geology Faculty Research Publications

Radial and azimuthal anisotropy in seismic wave speeds have long been observed using surface waves and are believed to be controlled by deformation within the Earth’s crust and uppermost mantle. Although radial and azimuthal anisotropy reflect important aspects of anisotropic media, few studies have tried to interpret them jointly. We describe a method of inversion that interprets simultaneous observations of radial and azimuthal anisotropy under the assumption of a hexagonally symmetric elastic tensor with a tilted symmetry axis defined by dip and strike angles. We show that observations of radial anisotropy and the 2ψ component of azimuthal anisotropy for Rayleigh …