Publications
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Persistent slip rate discrepancies in the eastern California (USA) shear zone Persistent slip rate discrepancies in the eastern California (USA) shear zone
Understanding fault slip rates in the eastern California shear zone (ECSZ) using GPS geodesy is complicated by potentially overlapping strain signals due to many sub-parallel strike-slip faults and by inconsistencies with geologic slip rates. The role of fault system geometry in describing ECSZ deformation may be investigated with total variation regularization, which algorithmically...
Authors
Eileen Evans, Wayne R. Thatcher, Frederick Pollitz, Jessica R. Murray
The water content of recurring slope lineae on Mars The water content of recurring slope lineae on Mars
Observations of recurring slope lineae (RSL) from the High-Resolution Imaging Science Experiment have been interpreted as present-day, seasonally variable liquid water flows; however, orbital spectroscopy has not confirmed the presence of liquid H2O, only hydrated salts. Thermal Emission Imaging System (THEMIS) temperature data and a numerical heat transfer model definitively constrain...
Authors
Christopher S. Edwards, Sylvain Piqueux
Elucidating the role of vegetation in the initiation of rainfall-induced shallow landslides: Insights from an extreme rainfall event in the Colorado Front Range Elucidating the role of vegetation in the initiation of rainfall-induced shallow landslides: Insights from an extreme rainfall event in the Colorado Front Range
More than 1100 debris flows were mobilized from shallow landslides during a rainstorm from 9 to 13 September 2013 in the Colorado Front Range, with the vast majority initiating on sparsely vegetated, south facing terrain. To investigate the physical processes responsible for the observed aspect control, we made measurements of soil properties on a densely forested north facing hillslope...
Authors
Luke McGuire, Francis K. Rengers, Jason W. Kean, Jeffrey A. Coe, Benjamin B. Mirus, Rex L. Baum, Jonathan W. Godt
Pleistocene Lake Bonneville as an analog for extraterrestrial lakes and oceans Pleistocene Lake Bonneville as an analog for extraterrestrial lakes and oceans
Geomorphic confirmation for a putative ancient Mars ocean relies on analog comparisons of coastal-like features such as shoreline feature attributes and temporal scales of process formation. Pleistocene Lake Bonneville is one of the few large, geologically young, terrestrial lake systems that exemplify well-preserved shoreline characteristics that formed quickly, on the order of a...
Authors
M.A. Chan, P. Jewell, T. J. Parker, J. Ormo, Chris Okubo, G. Komatsu
Dense lower crust elevates long-term earthquake rates in the New Madrid seismic zone Dense lower crust elevates long-term earthquake rates in the New Madrid seismic zone
Knowledge of the local state of stress is critical in appraising intraplate seismic hazard. Inverting earthquake moment tensors, we demonstrate that principal stress directions in the New Madrid seismic zone (NMSZ) differ significantly from those in the surrounding region. Faults in the NMSZ that are incompatible with slip in the regional stress field are favorably oriented relative to...
Authors
William Brower Levandowski, Oliver S. Boyd, Leonardo Ramirez-Guzman
Rapid estimation of earthquake magnitude from the arrival time of the peak high-frequency amplitude Rapid estimation of earthquake magnitude from the arrival time of the peak high-frequency amplitude
We propose a simple approach to measure earthquake magnitude M using the time difference (Top) between the body‐wave onset and the arrival time of the peak high‐frequency amplitude in an accelerogram. Measured in this manner, we find that Mw is proportional to 2logTop for earthquakes 5≤Mw≤7, which is the theoretical proportionality if Top is proportional to source dimension and stress...
Authors
Shunta Noda, Shunroku Yamamoto, William L. Ellsworth
The Earthquake‐Source Inversion Validation (SIV) Project The Earthquake‐Source Inversion Validation (SIV) Project
Finite‐fault earthquake source inversions infer the (time‐dependent) displacement on the rupture surface from geophysical data. The resulting earthquake source models document the complexity of the rupture process. However, multiple source models for the same earthquake, obtained by different research teams, often exhibit remarkable dissimilarities. To address the uncertainties in...
Authors
P. Martin Mai, Danijel Schorlemmer, Morgan T. Page, Jean-Paul Ampuero, Kimiyuki Asano, Mathieu Causse, Susana Custodio, Wenyuan Fan, Gaetano Festa, Martin Galis, Frantisek Gallovic, Walter Imperatori, Martin Kaser, Dmytro Malytskyy, Ryo Okuwaki, Frederick Pollitz, Luca Passone, Hoby N. T. Razafindrakoto, Haruko Sekiguchi, Seok Goo Song, Surendra N. Somala, Kiran K. S. Thingbaijam, Cedric Twardzik, Martin van Driel, Jagdish C. Vyas, Rongjiang Wang, Yuji Yagi, Olaf Zielke
The Eastern California Shear Zone as the northward extension of the southern San Andreas Fault The Eastern California Shear Zone as the northward extension of the southern San Andreas Fault
Cluster analysis offers an agnostic way to organize and explore features of the current GPS velocity field without reference to geologic information or physical models using information only contained in the velocity field itself. We have used cluster analysis of the Southern California Global Positioning System (GPS) velocity field to determine the partitioning of Pacific-North America...
Authors
Wayne R. Thatcher, James C. Savage, Robert W. Simpson
Noise reduction in long‐period seismograms by way of array summing Noise reduction in long‐period seismograms by way of array summing
Long‐period (>100 s period) seismic data can often be dominated by instrumental noise as well as local site noise. When multiple collocated sensors are installed at a single site, it is possible to improve the overall station noise levels by applying stacking methods to their traces. We look at the noise reduction in long‐period seismic data by applying the time–frequency phase‐weighted...
Authors
Adam T. Ringler, David C. Wilson, Tyler Storm, Benjamin T. Marshall, Charles R. Hutt, Austin Holland
Kinematic ground motion simulations on rough faults including effects of 3D stochastic velocity perturbations Kinematic ground motion simulations on rough faults including effects of 3D stochastic velocity perturbations
We describe a methodology for generating kinematic earthquake ruptures for use in 3D ground‐motion simulations over the 0–5 Hz frequency band. Our approach begins by specifying a spatially random slip distribution that has a roughly wavenumber‐squared fall‐off. Given a hypocenter, the rupture speed is specified to average about 75%–80% of the local shear wavespeed and the prescribed slip...
Authors
Robert Graves, Arben Pitarka
California State Waters Map Series — Offshore of Monterey, California California State Waters Map Series — Offshore of Monterey, California
Introduction In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection...
Authors
Samuel Y. Johnson, Peter Dartnell, Stephen R. Hartwell, Guy R. Cochrane, Nadine E. Golden, Janet Watt, Clifton W. Davenport, Rikk G. Kvitek, Mercedes D. Erdey, Lisa M. Krigsman, Ray W. Sliter, Katherine L. Maier
Hydra—The National Earthquake Information Center’s 24/7 seismic monitoring, analysis, catalog production, quality analysis, and special studies tool suite Hydra—The National Earthquake Information Center’s 24/7 seismic monitoring, analysis, catalog production, quality analysis, and special studies tool suite
This report provides an overview of the capabilities and design of Hydra, the global seismic monitoring and analysis system used for earthquake response and catalog production at the U.S. Geological Survey National Earthquake Information Center (NEIC). Hydra supports the NEIC’s worldwide earthquake monitoring mission in areas such as seismic event detection, seismic data insertion and...
Authors
John M. Patton, Michelle R. Guy, Harley M. Benz, Raymond P. Buland, Brian K. Erickson, David S. Kragness