Publications
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Low strength of deep San Andreas fault gouge from SAFOD core
The San Andreas fault accommodates 28–34 mm yr−1 of right lateral motion of the Pacific crustal plate northwestward past the North American plate. In California, the fault is composed of two distinct locked segments that have produced great earthquakes in historical times, separated by a 150-km-long creeping zone. The San Andreas Fault Observatory at Depth (SAFOD) is a scientific borehole located
Authors
David A. Lockner, Carolyn A. Morrow, Diane E. Moore, Stephen H. Hickman
An approach to modeling coupled thermal-hydraulic-chemical processes in geothermal systems
Interactions between hydrothermal fluids and rock alter mineralogy, leading to the formation of secondary minerals and potentially significant physical and chemical property changes. Reactive transport simulations are essential for evaluating the coupled processes controlling the geochemical, thermal and hydrological evolution of geothermal systems. The objective of this preliminary investigation
Authors
Jennifer Palguta, Colin F. Williams, Steven E. Ingebritsen, Stephen H. Hickman, Eric Sonnenthal
Electrical properties of methane hydrate + sediment mixtures
As part of our DOE-funded proposal to characterize gas hydrate in the Gulf of Mexico using marine electromagnetic methods, a collaboration between SIO, LLNL, and USGS with the goal of measuring the electrical properties of lab-created methane (CH4) hydrate and sediment mixtures was formed. We examined samples with known characteristics to better relate electrical properties measured in the field t
Authors
Wyatt L. Du Frane, Laura A. Stern, Karen A. Weitemeyer, Steven Constable, Jeffery J. Roberts
Deep rock damage in the San Andreas Fault revealed by P- and S-type fault-zone-guided waves
Damage to fault-zone rocks during fault slip results in the formation of a channel of low seismic-wave velocities. Within such channels guided seismic waves, denoted by Fg, can propagate. Here we show with core samples, well logs and Fg-waves that such a channel is crossed by the SAFOD (San Andreas Fault Observatory at Depth) borehole at a depth of 2.7 km near Parkfield, California, USA. This lat
Authors
William L. Ellsworth, Peter E. Malin
Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California
Investigation of a right-laterally offset channel at the Miller's Field paleoseismic site yields a late Holocene slip rate of 26.2 +6.4/−4.3 mm/yr (1σ) for the main trace of the San Andreas fault at Parkfield, California. This is the first well-documented geologic slip rate between the Carrizo and creeping sections of the San Andreas fault. This rate is lower than Holocene measurements along the C
Authors
N.A. Toke, J.R. Arrowsmith, Michael J. Rymer, A. Landgraf, D.E. Haddad, M. Busch, J. Coyan, A. Hannah
San Andreas fault earthquake chronology and Lake Cahuilla history at Coachella, California
The southernmost ~100 km of the San Andreas fault has not ruptured historically. It is imperative to determine its rupture history to better predict its future behavior. This paleoseismic investigation in Coachella, California, establishes a chronology of at least five and up to seven major earthquakes during the past ~1100 yr. This chronology yields a range of average recurrence intervals between
Authors
B. Philibosian, T. Fumal, R. Weldon
Estimating earthquake-rupture rates on a fault or fault system
Previous approaches used to determine the rates of different earthquakes on a fault have made assumptions regarding segmentation, have been difficult to document and reproduce, and have lacked the ability to satisfy all available data constraints. We present a relatively objective and reproducible inverse methodology for determining the rate of different ruptures on a fault or fault system. The da
Authors
E. H. Field, M.T. Page
Frictional strengths of talc-serpentine and talc-quartz mixtures
Talc is a constituent of faults in a variety of settings, and it may be an effective weakening agent depending on its abundance and distribution within a fault. We conducted frictional strength experiments under hydrothermal conditions to determine the effect of talc on the strengths of synthetic gouges of lizardite and antigorite serpentinites and of quartz. Small amounts of talc weaken serpentin
Authors
Diane E. Moore, D. A. Lockner
Epistemic uncertainty in the location and magnitude of earthquakes in Italy from Macroseismic data
Three independent techniques (Bakun and Wentworth, 1997; Boxer from Gasperini et al., 1999; and Macroseismic Estimation of Earthquake Parameters [MEEP; see Data and Resources section, deliverable D3] from R.M.W. Musson and M.J. Jimenez) have been proposed for estimating an earthquake location and magnitude from intensity data alone. The locations and magnitudes obtained for a given set of intensit
Authors
W. H. Bakun, Capera A. Gomez, M. Stucchi
Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer
We report on a broad and unprecedented increase in seismicity rate following the M=9.0 Tohoku mainshock for M ≥ 2 earthquakes over inland Japan, parts of the Japan Sea and Izu islands, at distances of up to 425 km from the locus of high (≥15 m) seismic slip on the megathrust. Such an increase was not seen for the 2004 M=9.1 Sumatra or 2010 M=8.8 Chile earthquakes, but they lacked the seismic netwo
Authors
S. Toda, R. S. Stein, J. Lin
Observations of changes in waveform character induced by the 1999 Mw7.6 Chi-Chi earthquake
We observe changes in the waveforms of repeating earthquakes in eastern Taiwan following the 1999 Mw7.6 Chi-Chi earthquake, while their recurrence intervals appear to be unaffected. There is a clear reduction in waveform similarity and velocity changes indicated by delayed phases at the time of the Chi-Chi event. These changes are limited to stations in and paths that cross the 70 × 100 km region
Authors
K.H. Chen, T. Furumura, J. Rubinstein, R.-J. Rau