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Exploring Background Noise With A Large-N Infrasound Array: Waterfalls, Thunderstorms, And Earthquakes, L. T. Scamfer, J. F. Anderson
Exploring Background Noise With A Large-N Infrasound Array: Waterfalls, Thunderstorms, And Earthquakes, L. T. Scamfer, J. F. Anderson
Geosciences Faculty Publications and Presentations
Ambient infrasound noise contains an abundance of information that is typically overlooked due to limitations of typical infrasound arrays. To evaluate the ability of large-N infrasound arrays to identify weak signals hidden in background noise, we examine data from a 22-element array in central Idaho, USA, spanning 58 days using a standard beamforming method. Our results include nearly continuous detections of diverse weak signals from infrasonic radiators, sometimes at surprising distances. We observe infrasound from both local (8 km) and distant (195 km) waterfalls. Thunderstorms and earthquakes are also notable sources, with distant thunderstorm infrasound observed from ∼800 to 900 …
A Broad, Distributed Active Fault Zone Lies Beneath Salt Lake City, Utah, Lee M. Liberty, James St. Clair, Adam P. Mckean
A Broad, Distributed Active Fault Zone Lies Beneath Salt Lake City, Utah, Lee M. Liberty, James St. Clair, Adam P. Mckean
Geosciences Faculty Publications and Presentations
Although the Wasatch fault is currently known to have a high‐seismic hazard from motion along range‐bounding faults, new seismic data reveal faulted and folded 13,000–30,000‐yr‐old Lake Bonneville strata beneath Salt Lake City (SLC). Coupled with previous excavation trench, borehole, and other geologic and geophysical observations, we conclude that a zone of latest Pleistocene and/or Holocene faulting and folding kinematically links the East Bench and Warm Springs faults through a 3 km wide relay structure and transfer zone. We characterize faults beneath downtown SLC as active, and these faults may displace or deform the ground surface during an earthquake. Through offset …
The 31 March 2020 MW 6.5 Stanley, Idaho, Earthquake: Seismotectonics And Preliminary Aftershock Analysis, Lee M. Liberty, Zachary M. Lifton, T. Dylan Mikesell
The 31 March 2020 MW 6.5 Stanley, Idaho, Earthquake: Seismotectonics And Preliminary Aftershock Analysis, Lee M. Liberty, Zachary M. Lifton, T. Dylan Mikesell
Geosciences Faculty Publications and Presentations
We report on the tectonic framework, seismicity, and aftershock monitoring efforts related to the 31 March 2020 Mw 6.5 Stanley, Idaho, earthquake. The earthquake sequence has produced both strike-slip and dip-slip motion, with minimal surface displacement or damage. The earthquake occurred at the northern limits of the Sawtooth normal fault. This fault separates the Centennial tectonic belt, a zone of active seismicity within the Basin and Range Province, from the Idaho batholith to the west and Challis volcanic belt to the north and east. We show evidence for a potential kinematic link between the northeast-dipping Sawtooth fault and the …
Resonant Frequency Derived From The Rayleigh‐Wave Dispersion Image: The High‐Impedance Boundary Problem, Lee M. Liberty, James St. Clair, T. Dylan Mikesell, William D. Schermerhorn
Resonant Frequency Derived From The Rayleigh‐Wave Dispersion Image: The High‐Impedance Boundary Problem, Lee M. Liberty, James St. Clair, T. Dylan Mikesell, William D. Schermerhorn
Geosciences Faculty Publications and Presentations
We present a simple and automated approach to estimate primary site‐response resonance, layer thickness, and shear‐wave velocity directly from a dispersion image for a layer over half‐space problem. We demonstrate this for high‐impedance boundary conditions that lie in the upper tens of meters. Our approach eliminates the need for time‐consuming dispersion curve picking and 1D shear‐wave velocity inversion for large data volumes that can capture velocity structure in profile. We highlight important relationships between dispersion characteristics and resonance parameters through synthetic modeling and field data acquired over Atlantic Coastal Plain sediments. In this environment, shallow soil conditions are critical to …
Characterizing Coseismic Ionospheric Disturbance For Surface-Rupturing Earthquakes, Rebekah Faith Lee
Characterizing Coseismic Ionospheric Disturbance For Surface-Rupturing Earthquakes, Rebekah Faith Lee
Boise State University Theses and Dissertations
Coseismic ionospheric disturbances (CID) are commonly identified using global navigation space system (GNSS) satellites. Little research, however, has focused on using total electron content (TEC) observations to characterize acoustic sources on Earth's surface. For this thesis, I investigate the applicability of an analytical method to invert the TEC for the acoustic wave. The inversion is based on the modeling of a transfer function. Deconvolving the TEC by the transfer function gives the acoustic wave. Inverting for the acoustic wave in this way would remove phase differences in the TEC created by atmospheric-ionospheric coupling. I test the assumption in the model …
Analyst A: Alternatives In Analysis Of The Utexas1 Surface Wave Dataset, Paul Michaels
Analyst A: Alternatives In Analysis Of The Utexas1 Surface Wave Dataset, Paul Michaels
Geosciences Faculty Publications and Presentations
In February of 2011 an earthquake event caused significant damage and loss of life in Christchurch, New Zealand. Such an event serves as motivation for improved foundation design and characterization of the shallow subsurface. In January of 2013, University of Texas engineers acquired surface wave data which has been made available to the ASCE GeoInstitute Geophysical Engineering Committee for a benchmark project. Participants were invited to process and interpret the common data set. This paper reports the results designated as those of "Analyst A". The active vibroseis and sledgehammer data were combined to produce a composite Rayleigh wave dispersion curve. …
Teaching Geophysics With A Vertical-Component Seismometer, Kasper Van Wijk, Ted Channel, Karen Viskupic, Martin L. Smith
Teaching Geophysics With A Vertical-Component Seismometer, Kasper Van Wijk, Ted Channel, Karen Viskupic, Martin L. Smith
Geosciences Faculty Publications and Presentations
Earthquakes are some of the more dramatic expressions of the dynamics of our planet. The sudden release of stress built up slowly by tectonic or volcanic processes often has far-reaching consequences, and can be measured (in classrooms) around the world. This is one reason why designing and building seismometers has been a popular activity,1,2 and why different versions of “Seismometer in Schools” projects thrive in the United States, Australia, and Europe. We present a cheap, robust, and easy-to-build seismometer—called the TC1 —to measure seismic displacements in the vertical direction. Its components are easy to obtain and assemble, yet the …
Establishing Confidence In Surface Wave Determined Soil Profiles, Paul Michaels
Establishing Confidence In Surface Wave Determined Soil Profiles, Paul Michaels
CGISS Publications and Presentations
Surface waves can be used to determine the shear velocity profile from the ground surface to some depth limited by the spectral band of the seismic source. A number of factors influence the uncertainties of the determined profile. The field acquisition factors include the deployment geometry of geophones, the spectral characteristics of the geophones, recording instruments, and seismic source. A key data processing factor is the determination of a dispersion curve from the field recordings. Finally, there are important choices in conducting the inversion of the dispersion curve which leads to the final soil profile. Even if the field factors …
Interpretation Of Rayleigh-Wave Ellipticity Observed With Multicomponent Passive Seismic Interferometry At Hekla Volcano, Iceland, Matthew M. Haney, Andrew Nies, Tim Masterlark, Sarah Needy, Rikke Pedersen
Interpretation Of Rayleigh-Wave Ellipticity Observed With Multicomponent Passive Seismic Interferometry At Hekla Volcano, Iceland, Matthew M. Haney, Andrew Nies, Tim Masterlark, Sarah Needy, Rikke Pedersen
CGISS Publications and Presentations
The 2010 eruption of Eyjafjallajökull has drawn increased attention to Iceland’s Eastern Volcanic Zone (EVZ) due to the threat it poses to the heavily used air-traffic corridors of the northern Atlantic Ocean. Within the EVZ, Hekla is historically one of the most active volcanoes and has exhibited a decadal eruption pattern for the past 40 years. Hekla most recently erupted in 2000 and is thus ripe for another decadal eruption. Because Hekla is generally aseismic, except for a brief time period (hours) leading up to an eruption, monitoring has previously depended on precursory deformation signals (Linde et al., 1993). As …
Hammer Seismic Reflection Imaging In An Urban Environment, Lee M. Liberty
Hammer Seismic Reflection Imaging In An Urban Environment, Lee M. Liberty
CGISS Publications and Presentations
Subsurface characterization within urban centers is critically important for city planners, municipalities, and engineers to estimate groundwater resources, track contaminants, assess earthquake or landslide hazards, and many other similar objectives. Improving geophysical imaging methods and results, while minimizing costs, provides greater opportunities for city/project planners and geophysicists alike to take advantage of the improved characterization afforded by the particular method. Seismic reflection results can provide hydrogeologic constraints for groundwater models, provide slip rate estimates for active faults, or simply map stratigraphy to provide target depth estimate. While many traditional urban seismic transects have included the use of vibroseis sources to …