Publications
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The crustal magma storage system of Volcán Quizapu, Chile, and the effects of magma mixing on magma diversity
Crystal zoning as well as temperature and pressure estimates from phenocryst phase equilibria are used to constrain the architecture of the intermediate-sized magmatic system (some tens of km3) of Volcán Quizapu, Chile, and to document the textural and compositional effects of magma mixing. In contrast to most arc magma systems, where multiple episodes of open-system behavior obscure the evidence
Authors
George W. Bergantz, Kari M. Cooper, Edward Hildreth, Phillipp Ruprecht
Observed source parameters for dynamic rupture with non-uniform initial stressand relatively high fracture energy
We have conducted dynamic rupture propagation experiments to establish the relations between in-source stress drop, fracture energy and the resulting particle velocity during slip of an unconfined 2 m long laboratory fault at normal stresses between 4 and 8 MPa. To produce high fracture energy in the source we use a rough fault that has a large slip weakening distance. An artifact of the high frac
Authors
Nicholas M. Beeler, Brian D. Kilgore, Arthur F. McGarr, Jon Peter B. Fletcher, John R. Evans, Steven R. Baker
Aftershocks halted by static stress shadows
Earthquakes impart static and dynamic stress changes to the surrounding crust. Sudden fault slip causes small but permanent—static—stress changes, and passing seismic waves cause large, but brief and oscillatory—dynamic—stress changes. Because both static and dynamic stresses can trigger earthquakes within several rupture dimensions of a mainshock, it has proven difficult to disentangle their cont
Authors
Shinji Toda, Ross S. Stein, Gregory C. Beroza, David Marsan
Sources of shaking and flooding during the Tohoku-Oki earthquake: a mixture of rupture styles
Modeling strong ground motions from great subduction zone earthquakes is one of the great challenges of computational seismology. To separate the rupture characteristics from complexities caused by 3D sub-surface geology requires an extraordinary data set such as provided by the recent Mw9.0 Tohoku-Oki earthquake. Here we combine deterministic inversion and dynamically guided forward simulation me
Authors
Shengji Wei, Robert Graves, Don Helmberger, Jean-Philippe Avouac, Junle Jiang
Significant motions between GPS sites in the New Madrid region: implications for seismic hazard
Position time series from Global Positioning System (GPS) stations in the New Madrid region were differenced to determine the relative motions between stations. Uncertainties in rates were estimated using a three‐component noise model consisting of white, flicker, and random walk noise, following the methodology of Langbein, 2004. Significant motions of 0.37±0.07 (one standard error) mm/yr were fo
Authors
Arthur Frankel, Robert Smalley, J. Paul
New Zealand’s deadliest quake sounds alarm for cities on fault lines
The catastrophic Christ Church Earthquake is a strong reminder to engineers and scientists of the hazards pose by fault lines, both mapped and unknown, near major cities. In February 2011, the relatively moderate earthquake that struck the cities of Christchurch and Lyttleton in the Canterbury region of New Zealand's South Island surprised many with its destructive power. The magnitude 6.2 temblor
Authors
Erol Kalkan
Seismic structure of the crust and uppermost mantle of South America and surrounding oceanic basins
We present a new set of contour maps of the seismic structure of South America and the surrounding ocean basins. These maps include new data, helping to constrain crustal thickness, whole-crustal average P-wave and S-wave velocity, and the seismic velocity of the uppermost mantle (Pn and Sn). We find that: (1) The weighted average thickness of the crust under South America is 38.17 km (standard de
Authors
Gary S. Chulick, Shane Detweiler, Walter D. Mooney
Thermodynamic method for generating random stress distributions on an earthquake fault
This report presents a new method for generating random stress distributions on an earthquake fault, suitable for use as initial conditions in a dynamic rupture simulation. The method employs concepts from thermodynamics and statistical mechanics. A pattern of fault slip is considered to be analogous to a micro-state of a thermodynamic system. The energy of the micro-state is taken to be the elast
Authors
Michael Barall, Ruth A. Harris
Validation of ground-motion simulations for historical events using SDoF systems
The study presented in this paper is among the first in a series of studies toward the engineering validation of the hybrid broadband ground‐motion simulation methodology by Graves and Pitarka (2010). This paper provides a statistical comparison between seismic demands of single degree of freedom (SDoF) systems subjected to past events using simulations and actual recordings. A number of SDoF syst
Authors
C. Galasso, F. Zareian, I. Iervolino, R.W. Graves
Timing of large earthquakes during the past 500 years along the Santa Cruz Mountains segment of the San Andreas fault at Mill Canyon, near Watsonville, California
A paleoseismic investigation across the Santa Cruz Mountains section of the San Andreas fault at Mill Canyon indicates that four surface‐rupturing earthquakes have occurred there during the past ~500 years. At this site, right‐lateral fault slip has moved a low shutter ridge across the mouth of the canyon, ponding latest Holocene sediments. These alluvial deposits are deformed along a narrow zone
Authors
Thomas E. Fumal
Contemporary seismicity in and around the Yakima-Fold-and-Thrust Belt in eastern Washington
We examined characteristics of routinely cataloged seismicity from 1970 to the present in and around the Yakima fold‐and‐thrust belt (YFTB) in eastern Washington to determine if the characteristics of contemporary seismicity provide clues about regional‐scale active tectonics or about more localized, near‐surface processes. We employed new structural and hydrologic models of the Columbia River bas
Authors
J. Gomberg, B. Sherrod, M. Trautman, E. Burns, Diane Snyder
Afterslip, tremor, and the Denali fault earthquake
We tested the hypothesis that afterslip should be accompanied by tremor using observations of seismic and aseismic deformation surrounding the 2002 M 7.9 Denali fault, Alaska, earthquake (DFE). Afterslip happens more frequently than spontaneous slow slip and has been observed in a wider range of tectonic environments, and thus the existence or absence of tremor accompanying afterslip may provide n
Authors
Joan Gomberg, Stephanie Prejean, Natalia Ruppert