Publications
Filter Total Items: 7240
Forecast experiment: do temporal and spatial b value variations along the Calaveras fault portend M ≥ 4.0 earthquakes?
The power law distribution of earthquake magnitudes and frequencies is a fundamental scaling relationship used for forecasting. However, can its slope (b value) be used on individual faults as a stress indicator? Some have concluded that b values drop just before large shocks. Others suggested that temporally stable low b value zones identify future large-earthquake locations. This study assesses
Authors
Tom Parsons
Tsunami warnings: Understanding in Hawai'i
The devastating southeast Asian tsunami of December 26, 2004 has brought home the destructive consequences of coastal hazards in an absence of effective warning systems. Since the 1946 tsunami that destroyed much of Hilo, Hawai‘i, a network of pole mounted sirens has been used to provide an early public alert of future tsunamis. However, studies in the 1960s showed that understanding of the meanin
Authors
Chris E. Gregg, Bruce F. Houghton, Douglas Paton, David M. Johnston, David A. Swanson, B.S. Yanagi
Pre-eruption recharge of the Bishop magma system
The 650 km3 rhyolitic Bishop Tuff (eastern California, USA), which is stratigraphically zoned with respect to temperatures of mineral equilibration, reflects a corresponding thermal gradient in the source magma chamber. Consistent with previous work, application of the new TitaniQ (Ti-in-quartz) thermometer to quartz phenocryst rims documents an ∼100 °C temperature increase with chamber depth at t
Authors
D.A. Wark, W. Hildreth, F.S. Spear, D.J. Cherniak, E.B. Watson
Hydrothermal fluid flow and deformation in large calderas: Inferences from numerical simulations
[1] Inflation and deflation of large calderas is traditionally interpreted as being induced by volume change of a discrete source embedded in an elastic or viscoelastic half-space, though it has also been suggested that hydrothermal fluids may play a role. To test the latter hypothesis, we carry out numerical simulations of hydrothermal fluid flow and poroelastic deformation in calderas by couplin
Authors
Shaul Hurwitz, L.B. Christiansen, Paul A. Hsieh
Subaqueous geology and a filling model for Crater Lake, Oregon
Results of a detailed bathymetric survey of Crater Lake conducted in 2000, combined with previous results of submersible and dredge sampling, form the basis for a geologic map of the lake floor and a model for the filling of Crater Lake with water. The most prominent landforms beneath the surface of Crater Lake are andesite volcanoes that were active as the lake was filling with water, following c
Authors
M. Nathenson, C. R. Bacon, D.W. Ramsey
Waveform inversion of volcano-seismic signals for an extended source
[1] We propose a method to investigate the dimensions and oscillation characteristics of the source of volcano-seismic signals based on waveform inversion for an extended source. An extended source is realized by a set of point sources distributed on a grid surrounding the centroid of the source in accordance with the source geometry and orientation. The source-time functions for all point sources
Authors
M. Nakano, Hiroyuki Kumagai, B. Chouet, P. Dawson
Implications of the 26 December 2004 Sumatra-Andaman earthquake on tsunami forecast and assessment models for great subduction-zone earthquakes
Results from different tsunami forecasting and hazard assessment models are compared with observed tsunami wave heights from the 26 December 2004 Indian Ocean tsunami. Forecast models are based on initial earthquake information and are used to estimate tsunami wave heights during propagation. An empirical forecast relationship based only on seismic moment provides a close estimate to the observed
Authors
Eric L. Geist, Vasily V. Titov, Diego Arcas, Fred F. Pollitz, Susan L. Bilek
Effects of wastewater disinfection on waterborne bacteria and viruses
Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. In most circumstances, the efficacy of a wastewater disinfection process is regulated and monitored based on measurements of the responses of indicator bacteria. However, inactivation of indicator bacteria does not guarantee an acceptable degree of inactivation among other waterborn
Authors
E. R. Blatchley, W.-L. Gong, J.E. Alleman, J.B. Rose, D.E. Huffman, M. Otaki, J.T. Lisle
Evidence for and implications of sedimentary diapirism and mud volcanism in the southern Utopia highland-lowland boundary plain, Mars
Several types of spatially associated landforms in the southern Utopia Planitia highland–lowland boundary (HLB) plain appear to have resulted from localized geologic activity, including (1) fractured rises, (2) elliptical mounds, (3) pitted cones with emanating lobate materials, and (4) isolated and coalesced cavi (depressions). Stratigraphic analysis indicates these features are Hesperian or youn
Authors
James A. Skinner, Kenneth L. Tanaka
Geologic mapping of the Amirani-Gish Bar region of Io: Implications for the global geologic mapping of Io
We produced the first geologic map of the Amirani-Gish Bar region of Io, the last of four regional maps generated from Galileo mission data. The Amirani-Gish Bar region has five primary types of geologic materials: plains, mountains, patera floors, flows, and diffuse deposits. The flows and patera floors are thought to be compositionally similar, but are subdivided based on interpretations regardi
Authors
David A. Williams, Laszlo P. Keszthelyi, David A. Crown, Windy L. Jaeger, Paul M. Schenk
Why the sacramento delta area differs from other parts of the great valley: numerical modeling of thermal structure and thermal subsidence of forearc basins
Data on present-day heat flow, subsidence history, and paleotemperature for the Sacramento Delta region, California, have been employed to constrain a numerical model of tectonic subsidence and thermal evolution of forearc basins. The model assumes an oceanic basement with an initial thermal profile dependent on its age subjected to refrigeration caused by a subducting slab. Subsidence in the Sacr
Authors
V.O. Mikhailov, T. Parsons, R. W. Simpson, E.P. Timoshkina, C. Williams
Ensuring confidence in radionuclide-based sediment chronologies and bioturbation rates
Sedimentary records of naturally occurring and fallout-derived radionuclides are widely used as tools for estimating both the ages of recent sediments and rates of sedimentation and bioturbation. Developing these records to the point of data interpretation requires careful sample collection, processing, analysis and data modeling. In this work, we document a number of potential pitfalls that can i
Authors
John Crusius, Timothy C. Kenna