Publications
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Geomorphic and geologic controls of geohazards induced by Nepal’s 2015 Gorkha earthquake
The Gorkha earthquake (magnitude 7.8) on 25 April 2015 and later aftershocks struck South Asia, killing ~9000 people and damaging a large region. Supported by a large campaign of responsive satellite data acquisitions over the earthquake disaster zone, our team undertook a satellite image survey of the earthquakes’ induced geohazards in Nepal and China and an assessment of the geomorphic, tectonic
Authors
J.S. Kargel, G.J. Leonard, D. H. Shugar, U. K. Haritashya, A. Bevington, E.J. Fielding, K. Fujita, M. Geertsema, E. S. Miles, J. Steiner, E. Anderson, S. Bajracharya, G.W. Bawden, D. F. Breashears, A. Byers, B. Collins, M. R. Dhital, A. Donnellan, T. L. Evans, M. L. Geai, M. T. Glasscoe, D. Green, D. R. Gurung, R. Heijenk, A. Hilborn, K. Hudnut, C. Huyck, W. W. Immerzeel, Jiang Li, R. Jibson, A. Kaab, N. R. Khanal, D. Kirschbaum, P. D. A. Kraaijenbrink, D. Lamsal, Liu Shiyin, Lv Mingyang, D. McKinney, N. K. Nahirnick, Nan Zhuotong, S. Ojha, J. Olsenholler, T. H. Painter, M. Pleasants, K. C. Pratima, Q. I. Yuan, B.H. Raup, D. Regmi, D. R. Rounce, A. Sakai, Shangguan Donghui, J. M. Shea, A. B. Shrestha, A. Shukla, D. Stumm, M. van der Kooij, K. Voss, Wang Xin, B. Weihs, Wu Lizong, Yao Xiaojun, M. R. Yoder, N. Young
“Ductile to brittle” transition in thermally stable antigorite gouge at mantle pressures
General shear experiments on antigorite-rich serpentinite show a transition from ductile (distributed) to brittle (localized) deformation with increasing temperature from 300°C to 500°C at confining pressures from 1 to 2 GPa. The coefficient of friction associated with slip along fractures decreases from 0.23 to 0.07 with an increase in temperature from 300°C to 500°C. Velocity stepping experiment
Authors
Brooks P. Proctor, Greg Hirth
Afterslip behavior following the M6.0, 2014 South Napa earthquake with implications for afterslip forecasting on other seismogenic faults
The M6.0, 24 Aug. 2014 South Napa, California, earthquake exhibited unusually large slip for a California strike-slip event of its size with a maximum coseismic surface slip of 40-50 cm in the north section of the 15 km-long rupture. Although only minor (
Authors
James J. Lienkaemper, Stephen B. DeLong, Carolyn J Domrose, Carla M. Rosa
Lithospheric rheology constrained from twenty-five years of postseismic deformation following the 1989 Mw 6.9 Loma Prieta earthquake
The October 17, 1989 Mw 6.9 Loma Prieta earthquake provides the first opportunity of probing the crustal and upper mantle rheology in the San Francisco Bay Area since the 1906 Mw 7.9 San Francisco earthquake. Here we use geodetic observations including GPS and InSAR to characterize the Loma Prieta earthquake postseismic displacements from 1989 to 2013. Pre-earthquake deformation rates are constrai
Authors
Mong-Han Huang, Roland Burgmann, Fred Pollitz
Comparison of measurement- and proxy-based Vs30 values in California
This study was prompted by the recent availability of a significant amount of openly accessible measured VS30 values and the desire to investigate the trend of using proxy-based models to predict VS30 in the absence of measurements. Comparisons between measured and model-based values were performed. The measured data included 503 VS30 values collected from various projects for 482 seismographic st
Authors
Alan K. Yong
Effective stress, friction and deep crustal faulting
Studies of crustal faulting and rock friction invariably assume the effective normal stress that determines fault shear resistance during frictional sliding is the applied normal stress minus the pore pressure. Here we propose an expression for the effective stress coefficient αf at temperatures and stresses near the brittle-ductile transition (BDT) that depends on the percentage of solid-solid co
Authors
N.M. Beeler, Greg Hirth, Amanda M. Thomas, Roland Burgmann
Compilation of VS30 Data for the United States
VS30, the time-averaged shear-wave velocity (VS) to a depth of 30 meters, is a key index adopted by the earthquake engineering community to account for seismic site conditions. VS30 is typically based on geophysical measurements of VS derived from invasive and noninvasive techniques at sites of interest. Owing to cost considerations, as well as logistical and environmental concerns, VS30 data are
Authors
Alan Yong, Eric M. Thompson, David J. Wald, Keith L. Knudsen, Jack K. Odum, William J. Stephenson, Scott Haefner
Determining generic velocity and density models for crustal amplification calculations, with an update of the Boore and Joyner (1997) Generic Site Amplification for Graphic Site Amplification
This short note contains two contributions related to deriving depth‐dependent velocity and density models for use in computing generic crustal amplifications. The first contribution is a method for interpolating two velocity profiles to obtain a third profile with a time‐averaged velocity to depth Z that is equal to a specified value (e.g., for shear‐wave velocity VS, for Z=30 m, in which the
Authors
David Boore
Differential uplift and incision of the Yakima River terraces, central Washington State
The fault-related Yakima folds deform Miocene basalts and younger deposits of the Columbia Plateau in central Washington State. Geodesy implies ~2 mm/yr of NNE directed shortening across the folds, but until now the distribution and rates of Quaternary deformation among individual structures has been unclear. South of Ellensburg, Washington, the Yakima River cuts a ~600 m deep canyon across severa
Authors
Adrian M. Bender, Colin B. Amos, Paul R. Bierman, Dylan Rood, Lydia M. Staisch, Harvey M. Kelsey, Brian L. Sherrod
Evolution of fracture permeability of ultramafic rocks undergoing serpentinization at hydrothermal conditions: An experimental study
We performed flow-through laboratory experiments on five cylindrically cored samples of ultramafic rocks, in which we generated a well-mated through-going tensile fracture, to investigate evolution of fracture permeability during serpentinization. The samples were tested in a triaxial loading machine at a confining pressure of 50 MPa, pore pressure of 20 MPa, and temperature of 260°C, simulating a
Authors
Aida Farough, Diane E. Moore, David A. Lockner, R.P. Lowell
Seismic velocity structure of the crust and shallow mantle of the Central and Eastern United States by seismic surface wave imaging
Seismic surface waves from the Transportable Array of EarthScope's USArray are used to estimate phase velocity structure of 18 to 125 s Rayleigh waves, then inverted to obtain three-dimensional crust and upper mantle structure of the Central and Eastern United States (CEUS) down to ∼200 km. The obtained lithosphere structure confirms previously imaged CEUS features, e.g., the low seismic-velocity
Authors
Fred Pollitz, Walter D. Mooney
Along-strike variations in fault frictional properties along the San Andreas Fault near Cholame, California from joint earthquake and low-frequency earthquake relocations
Recent observations of low‐frequency earthquakes (LFEs) and tectonic tremor along the Parkfield–Cholame segment of the San Andreas fault suggest slow‐slip earthquakes occur in a transition zone between the shallow fault, which accommodates slip by a combination of aseismic creep and earthquakes (<15 km depth), and the deep fault, which accommodates slip by stable sliding (>35 km depth). However,
Authors
Rebecca M. Harrington, Elizabeth S. Cochran, Emily M. Griffiths, Xiangfang Zeng, Clifford H. Thurber