Two-dimensional elastic pseudo-spectral modeling of wide-aperture seismic array data with application to the Wichita Uplift-Anadarko Basin region of southwestern Oklahoma

1990 ◽  
Vol 80 (6A) ◽  
pp. 1677-1695 ◽  
Author(s):  
Ik Bum Kang ◽  
George A. McMechan
Keyword(s):  
Large Scale ◽  
Deep Structure ◽  
Sedimentary Basins ◽  
P Wave ◽  
Two Dimensional ◽  
Anadarko Basin ◽  
Near Surface ◽  
University Of Texas ◽  
Wide Aperture ◽  
The University

Abstract Full wave field modeling of wide-aperture data is performed with a pseudospectral implementation of the elastic wave equation. This approach naturally produces three-component stress and two-component particle displacement, velocity, and acceleration seismograms for compressional, shear, and Rayleigh waves. It also has distinct advantages in terms of computational requirements over finite-differencing when data from large-scale structures are to be modeled at high frequencies. The algorithm is applied to iterative two-dimensional modeling of seismograms from a survey performed in 1985 by The University of Texas at El Paso and The University of Texas at Dallas across the Anadarko basin and the Wichita Mountains in southwestern Oklahoma. The results provide an independent look at details of near-surface structure and reflector configurations. Near-surface (<3 km deep) structure and scattering effects account for a large percentage (>70 per cent) of the energy in the observed seismograms. The interpretation of the data is consistent with the results of previous studies of these data, but provides considerably more detail. Overall, the P-wave velocities in the Wichita Uplift are more typical of the middle crust than the upper crust (5.3 to 7.1 km/sec). At the surface, the uplift is either exposed as weathered outcrop (5.0 to 5.3 km/sec) or is overlain with sediments of up to 0.4 km in thickness, ranging in velocity from 2.7 to 3.4 km/sec, generally increasing with depth. The core of the uplift is relatively seismically transparent. A very clear, coherent reflection is observed from the Mountain View fault, which dips at ≈40° to the southwest, to at least 12 km depth. Velocities in the Anadarko Basin are typical of sedimentary basins; there is a general increase from ≈2.7 km/sec at the surface to ≈5.9 km/sec at ≈16 km depth, with discontinuous reflections at depths of ≈8, 10, 12, and 16 km.

2-D tomographic imaging of velocities in the Wichita uplift-Anadarko basin region of southwestern Oklahoma

1989 ◽  
Vol 79 (3) ◽  
pp. 873-887 ◽  
Author(s):  
Xianhuai Zhu ◽  
George A. McMechan
Keyword(s):  
High Velocity ◽  
El Paso ◽  
Tomographic Imaging ◽  
P Wave ◽  
Crustal Material ◽  
Low Velocity ◽  
Anadarko Basin ◽  
University Of Texas ◽  
Seismic Experiment ◽  
The University

Abstract In January of 1985, a densely-recorded, wide-aperture seismic experiment was performed by the University of Texas at El Paso and at Dallas, across the southwestern Oklahoma aulacogen. A two-dimensional P-wave velocity distribution is estimated for the Wichita uplift, the Anadarko basin, and the interface between them, by iterative tomographic imaging of travel-time picks from seven shots located near the 100-km-long recording line. The region that is imaged is roughly triangular in shape, with depth = 0 km at the ends of line and ≈ 15 km near its center. The main features that are revealed are a high-velocity (>6.8 km/sec) central core in the Wichita uplift and an asymmetrical Anadarko basin with decreasing velocities toward the basin axis. There are indications, within the uplift, of local high-velocity sills and a local low-velocity region that may be a remnant of normal crustal material.

scholarly journals Subsurface characterization of a quick-clay vulnerable area using near-surface geophysics and hydrological modelling

Solid Earth ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 1685-1705
Author(s):  
Silvia Salas-Romero ◽  
Alireza Malehmir ◽  
Ian Snowball ◽  
Benoît Dessirier
Keyword(s):  
Large Scale ◽  
Geophysical Methods ◽  
Hydrological Modelling ◽  
P Wave ◽  
Coarse Grained ◽  
Near Surface ◽  
Reflection Seismic ◽  
Geotechnical Investigations ◽  
Quick Clay ◽  
Near Surface Geophysics

Abstract. Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identify coarse-grained materials associated with the development of quick clays. We present the results of reflection seismic investigations on land and in part of the Göta River in Sweden, along which many quick-clay landslide scars exist. This is the first time that such a large-scale reflection seismic investigation has been carried out to study the subsurface structures associated with quick-clay landslides. The results also show a reasonable correlation with radio magnetotelluric and travel-time tomography models of the subsurface. Other ground geophysical data, such as high magnetic values, suggest a positive correlation with an increased thickness of the coarse-grained layer and shallower depths to the top of the bedrock and the top of the coarse-grained layer. The morphology of the river bottom and riverbanks, e.g. subaquatic landslide deposits, is shown by side-scan sonar and bathymetric data. Undulating bedrock, covered by subhorizontal sedimentary glacial and postglacial deposits, is clearly revealed. An extensive coarse-grained layer (P-wave velocity mostly between 1500 and 2500 m s−1 and resistivity from approximately 80 to 100 Ωm) exists within the sediments and is interpreted and modelled in a regional context. Several fracture zones are identified within the bedrock. Hydrological modelling of the coarse-grained layer confirms its potential for transporting fresh water infiltrated in fractures and nearby outcrops located in the central part of the study area. The modelled groundwater flow in this layer promotes the leaching of marine salts from the overlying clays by seasonal inflow–outflow cycles and/or diffusion, which contributes to the formation of potential quick clays.

scholarly journals Seismic investigations of the Martian near-surface at the InSight landing site

2020 ◽  
Author(s):  
Cedric Schmelzbach ◽  
Nienke Brinkman ◽  
David Sollberger ◽  
Sharon Kedar ◽  
Matthias Grott ◽  
...  
Keyword(s):  
Deep Structure ◽  
Landing Site ◽  
P Wave ◽  
Mission Design ◽  
Normal Operation ◽  
Seismic Signals ◽  
Martian Surface ◽  
Broadband Seismometer ◽  
Near Surface ◽  
Martian Regolith

<p>The InSight ultra-sensitive broadband seismometer package (SEIS) was installed on the Martian surface with the goal to study the seismicity on Mars and the deep interior of the Planet. A second surface-based instrument, the heat flow and physical properties package HP<sup>3</sup>, was placed on the Martian ground about 1.1 m away from SEIS. HP<sup>3</sup> includes a self-hammering probe called the ‘mole’ to measure the heat coming from Mars' interior at shallow depth to reveal the planet's thermal history. While SEIS was designed to study the deep structure of Mars, seismic signals such as the hammering ‘noise’ as well as ambient and other instrument-generated vibrations allow us to investigate the shallow subsurface. The resultant near-surface elastic property models provide additional information to interpret the SEIS data and allow extracting unique geotechnical information on the Martian regolith.</p><p>The seismic signals recorded during HP<sup>3</sup> mole operations provide information about the mole attitude and health as well as shed light on the near-surface, despite the fact that the HP<sup>3 </sup>mole continues to have difficulty penetrating below 40 cm (one mole length). The seismic investigation of the HP<sup>3</sup> hammering signals, however, was not originally planned during mission design and hence faced several technical challenges. For example, the anti-aliasing filters of the seismic-data acquisition chain were adapted when recording the mole hammering to allow recovering information above the nominal Nyquist frequency. In addition, the independently operating SEIS, HP<sup>3</sup> and lander clocks had to be correlated more frequently than in normal operation to enable high-precision timing.</p><p>To date, the analysis of the hammering signals allowed us to constrain the bulk P-wave velocity of the volume between the mole tip and SEIS (top 30 cm) to around 120 m/s. This low velocity value is compatible with laboratory tests performed on Martian regolith analogs with a density of around 1500 kg/m<sup>3</sup>. Furthermore, the SEIS leveling system resonances, seismic recordings of atmospheric pressure signals, HP<sup>3</sup> housekeeping data, and imagery provide additional constraints to establish a first seismic model of the shallow (topmost meters) subsurface at the landing site.</p>

The Cultural Affiliations and Chronological Position of the Clear Fork Focus

1947 ◽  
Vol 13 (2) ◽  
pp. 97-109 ◽  
Author(s):  
J. Charles Kelley
Keyword(s):  
Large Scale ◽  
Temporal Distribution ◽  
University Of Texas ◽  
Projectile Points ◽  
Additional Information ◽  
Central Texas ◽  
The University ◽  
Relationship Of ◽  
Archaeological Cultures ◽  
The Relationship

The importance of the Clear Fork Focus as a pre-pottery archaeological complex of north-central Texas has become generally known to archaeologists through the industry of its discoverer and principal proponent, Dr. Cyrus N. Ray, of Abilene, Texas. Unfortunately, the relationship of this complex to other and comparable archaeological cultures of Texas has been largely neglected and some regrettable misinformation in regard to its chronological position has been widely disseminated. In this paper the cultural affiliations and age of the Clear Fork Focus will be discussed in terms of the evidence presented by its discoverers and from the standpoint of new data derived from large scale excavations completed by the University of Texas in the terraces of the Colorado River near Austin, Texas. Additional information obtained by the writer through study of some twelve thousand projectile points from central, south, and western Texas, and their geographic and temporal distribution also is used.

THEORETICAL MAGNETOTELLURIC AND TURAM RESPONSE FROM TWO‐DIMENSIONAL INHOMOGENEITIES

Geophysics ◽  
1971 ◽  
Vol 36 (1) ◽  
pp. 38-52 ◽  
Author(s):  
Charles M. Swift
Keyword(s):  
Numerical Solutions ◽  
Deep Structure ◽  
Solution Technique ◽  
Two Dimensional ◽  
Near Surface ◽  
Anomalous Field ◽  
Strike Direction ◽  
Conductivity Structure ◽  
Representative Model ◽  
Infinite Line

The “network solution” technique for obtaining numerical solutions to Maxwell’s equations in two‐dimensional inhomogeneous media, originally developed by Madden, is presented in detail in this paper. By using plane‐wave and infinite line‐current sources respectively, theoretical magnetotelluric and Turam responses can be calculated above and within an arbitrarily complex two‐dimensional earth conductivity structure. Analysis of a few representative model results emphasizes the importance of considering all the electromagnetic field components, particularly those of the anomalous field. In magnetotellurics, the vertical magnetic field is useful in determining strike direction, and only the E parallel apparent resistivities are representative of deep structure in the presence of near‐surface conductivity inhomogeneities. In Turam, a finite resistivity background causes buried conductors to appear deeper and more conductive than they would appear if the background had infinite resistivity; and strong conductors can affect the total field sufficiently to cause screening.

scholarly journals Innovating for student success: The University Leadership Network (ULN) and tiered undergraduate peer mentor model

2017 ◽  
Vol 28 (3) ◽  
Author(s):  
Jennifer L. Smith
Keyword(s):  
Student Success ◽  
Large Scale ◽  
Critical Role ◽  
Underrepresented Minority ◽  
University Leadership ◽  
Peer Mentor ◽  
First Year Students ◽  
University Of Texas ◽  
The University ◽  
Mentor Model

This paper highlights the innovative approach the Student Success Initiative’s unit at the University of Texas at Austin is taking to increase undergraduate persistence and four-year graduation rates. Specifically, this piece explores the large-scale University Leadership Network (ULN) program and examines the tiered undergraduate peer mentor model utilized to support the success of first-year students from low-socioeconomic backgrounds, including a majority of underrepresented minority (URM) students. The article also reviews the critical role peer mentors play in helping to meet institution-wide goals and how they extend the reach of student support programs. Lastly, best practices, challenges, and components necessary for program replication will be presented.

scholarly journals On the Utility of Horizontal-to-Vertical Spectral Ratios of Ambient Noise in Joint Inversion with Rayleigh Wave Dispersion Curves for the Large-N Maupasacq Experiment

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5946
Author(s):  
Maik Neukirch ◽  
Antonio García-Jerez ◽  
Antonio Villaseñor ◽  
Francisco Luzón ◽  
Jacques Brives ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Large Scale ◽  
Joint Inversion ◽  
Dispersion Curves ◽  
P Wave ◽  
Gravity Inversion ◽  
Spectral Ratios ◽  
Near Surface ◽  
Dispersion Data ◽  
Short Period

Horizontal-to-Vertical Spectral Ratios (HVSR) and Rayleigh group velocity dispersion curves (DC) can be used to estimate the shallow S-wave velocity (VS) structure. Knowing the VS structure is important for geophysical data interpretation either in order to better constrain data inversions for P-wave velocity (VP) structures such as travel time tomography or full waveform inversions or to directly study the VS structure for geo-engineering purposes (e.g., ground motion prediction). The joint inversion of HVSR and dispersion data for 1D VS structure allows characterising the uppermost crust and near surface, where the HVSR data (0.03 to 10s) are most sensitive while the dispersion data (1 to 30s) constrain the deeper model which would, otherwise, add complexity to the HVSR data inversion and adversely affect its convergence. During a large-scale experiment, 197 three-component short-period stations, 41 broad band instruments and 190 geophones were continuously operated for 6 months (April to October 2017) covering an area of approximately 1500km2 with a site spacing of approximately 1 to 3km. Joint inversion of HVSR and DC allowed estimating VS and, to some extent density, down to depths of around 1000m. Broadband and short period instruments performed statistically better than geophone nodes due to the latter’s gap in sensitivity between HVSR and DC. It may be possible to use HVSR data in a joint inversion with DC, increasing resolution for the shallower layers and/or alleviating the absence of short period DC data, which may be harder to obtain. By including HVSR to DC inversions, confidence improvements of two to three times for layers above 300m were achieved. Furthermore, HVSR/DC joint inversion may be useful to generate initial models for 3D tomographic inversions in large scale deployments. Lastly, the joint inversion of HVSR and DC data can be sensitive to density but this sensitivity is situational and depends strongly on the other inversion parameters, namely VS and VP. Density estimates from a HVSR/DC joint inversion should be treated with care, while some subsurface structures may be sensitive, others are clearly not. Inclusion of gravity inversion to HVSR/DC joint inversion may be possible and prove useful.

scholarly journals Analysis of Prehistoric Artifacts from 2003 Excavations at the George C. Davis Site (41CE19), Cherokee County, Texas

2010 ◽  
Author(s):  
Perttula
Keyword(s):  
Large Scale ◽  
Small Sample ◽  
Geophysical Survey ◽  
Historic Site ◽  
University Of Texas ◽  
Pottery Sherds ◽  
The University ◽  
Geophysical Anomalies ◽  
Archaeological Excavations

A small sample of artifacts were recovered in 2003 archaeological excavations at the George C. Davis site (Caddoan Mounds State Historic Site) by The University of Texas at Austin. The work was done in conjunction with a large-scale geophysical survey of the site to locate archaeologically significant geophysical anomalies (i.e. Caddo structures, pit features, palisades, burial features, etc.). The excavations in Unit 113, ca. 150 m east of Mound B (Figure 1), were focused on Feature 237, a kind of circular Caddo structure called a “Button House” because of its four support posts around a central hearth feature. The principal kinds of artifacts found in the work include plain and decorated Caddo pottery sherds (40%), lithic debris (27%), and small pieces of what appears to be a glauconitic-rich clay (18%) that are likely not naturally found in the soils at the site. Appendix 1 provides an inventory, by provenience, of the recovered artifacts.

scholarly journals Growth, coalescence, and etching of two-dimensional overlayers on metals modulated by near-surface Ar nanobubbles

Nano Research ◽  
2021 ◽  
Author(s):  
Wei Wei ◽  
Jiaqi Pan ◽  
Haiping Lin ◽  
Chanan Euaruksakul ◽  
Zhiyun Li ◽  
...  
Keyword(s):  
Large Scale ◽  
2D Materials ◽  
Growth Front ◽  
Scale Production ◽  
Two Dimensional ◽  
Near Surface ◽  
Substrate Interaction ◽  
Large Scale Production ◽  
Surface Catalysis ◽  
Surface Measurements

AbstractThe synthesis of high-quality ultrathin overlayers is critically dependent on the surface structure of substrates, especially involving the overlayer-substrate interaction. By using in situ surface measurements, we demonstrate that the overlayer-substrate interaction can be tuned by doping near-surface Ar nanobubbles. The interfacial coupling strength significantly decreases with near-surface Ar nanobubbles, accompanying by an “anisotropic to isotropic” growth transformation. On the substrate containing near-surface Ar, the growth front crosses entire surface atomic steps in both uphill and downhill directions with no difference, and thus, the morphology of the two-dimensional (2D) overlayer exhibits a round-shape. Especially, the round-shaped 2D overlayers coalesce seamlessly with a growth acceleration in the approaching direction, which is barely observed in the synthesis of 2D materials. This can be attributed to the immigration lifetime and diffusion rate of growth species, which depends on the overlayer-substrate interaction and the surface catalysis. Furthermore, the “round to hexagon” morphological transition is achieved by etching-regrowth, revealing the inherent growth kinetics under quasi-freestanding conditions. These findings provide a novel promising way to modulate the growth, coalescence, and etching dynamics of 2D materials on solid surfaces by adjusting the strength of overlayer-substrate interaction, which contributes to optimization of large-scale production of 2D material crystals.

Altering Avalonia: oxygen isotopes and terrane distinction in the Appalachian peri-Gondwanan realmLaboratory for Stable Isotope Science (LSIS), The University of Western Ontario, Contribution 236.

2008 ◽  
Vol 45 (7) ◽  
pp. 815-825 ◽  
Author(s):  
Joanna Potter ◽  
Frederick J. Longstaffe ◽  
Sandra M. Barr ◽  
Margaret D. Thompson ◽  
Chris E. White
Keyword(s):  
Large Scale ◽  
Sedimentary Basins ◽  
Igneous Rocks ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Fluid Infiltration ◽  
Geochemical Fingerprint ◽  
Appalachian Orogen ◽  
Late Neoproterozoic ◽  
The University

Distinct 18O depletion is characteristic of a large majority of the 620–550 Ma felsic igneous rocks of Avalonia in the northern Appalachian orogen. Neoproterozoic rocks in the Boston Avalon terrane have the lowest δ18OWR values (≥–3.1‰), followed by the Mira terrane in Cape Breton Island and the Caledonia terrane in New Brunswick (≥–1.2‰), the Avalon terrane in Newfoundland (≥+2.8‰), and the Antigonish Highlands in Nova Scotia (≥+5.3‰). In contrast, this depletion of 18O is observed in very few of the Paleozoic felsic igneous rocks from these Avalonian terranes, and also in very few of the Neoproterozoic and Paleozoic felsic igneous rocks from the inboard Ganderian terranes. The low-18O character of the Neoproterozoic igneous rocks is related to regional pervasive, post-magmatic alteration by predominantly meteoric-hydrothermal fluids (δ18OH2O ∼–6‰ to –4‰) at 200–450 °C. The alteration likely occurred during late Neoproterozoic transtensional extension of Avalonia. Large-scale fluid infiltration and circulation within the Avalonian crust accompanied this extension with development of pull-apart sedimentary basins and extension-related magmatism that were the prelude to Cambrian submergence of Avalonia. This regional 18O depletion provides a geochemical fingerprint by which Avalonia can be distinguished from other peri-Gondwanan terranes. These data suggest that Avalonia existed as a composite terrane on the Gondwanan margin in the Neoproterozoic, separate from Ganderia.

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