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At least 19 recordsLinked to original sources
USGS2017

Book review: Physics of tsunamis

“Physics of Tsunamis” , second edition, provides a comprehensive analytical treatment of the hydrodynamics associated with the tsunami generation process. The book consists of seven chapters covering 388 pages. Because the subject matter within each chapter is distinct, an abstract appears at the beginning and references appear at the end of each chapter, rather than at the end of the book. Various topics of tsunami physics are examined largely from a theoretical perspective, although there is little information on how the physical descriptions are applied in numerical models. “ Physics of Tsunamis ”, by B. W. Levin and M. A. Nosov, Second Edition, Springer, 2016; ISBN-10: 33-1933106X, ISBN-13: 978-331933-1065

Pure and Applied Geophysics↗
USGS2008

Cancellation of spurious arrivals in Green's function extraction and the generalized optical theorem

The extraction of the Green's function by cross correlation of waves recorded at two receivers nowadays finds much application. We show that for an arbitrary small scatterer, the cross terms of scattered waves give an unphysical wave with an arrival time that is independent of the source position. This constitutes an apparent inconsistency because theory predicts that such spurious arrivals do not arise, after integration over a complete source aperture. This puzzling inconsistency can be resolved for an arbitrary scatterer by integrating the contribution of all sources in the stationary phase approximation to show that the stationary phase contributions to the source integral cancel the spurious arrival by virtue of the generalized optical theorem. This work constitutes an alternative derivation of this theorem. When the source aperture is incomplete, the spurious arrival is not canceled and could be misinterpreted to be part of the Green's function. We give an example of how spurious arrivals provide information about the medium complementary to that given by the direct and scattered waves; the spurious waves can thus potentially be used to better constrain the medium. ?? 2008 The American Physical Society.

Physical Review E - Statistical, Nonlinear, and So↗
USGS2003

Power-law tail probabilities of drainage areas in river basins

The significance of power-law tail probabilities of drainage areas in river basins was discussed. The convergence to a power law was not observed for all underlying distributions, but for a large class of statistical distributions with specific limiting properties. The article also discussed about the scaling properties of topologic and geometric network properties in river basins.

Physical Review E - Statistical, Nonlinear, and So↗
USGS2001

Land-use changes and the physical habitat of streams - a review with emphasis on studies within the U.S. Geological Survey Federal-State Cooperative Program

Understanding the links between land-use changes and physical stream habitat responses is of increasing importance to guide resource management and stream restoration strategies. Transmission of runoff and sediment to streams can involve complex responses of drainage basins, including time lags, thresholds, and cumulative effects. Land-use induced runoff and sediment yield often combine with channel-scale disturbances that decrease flow resistance and erosion resistance, or increase stream energy. The net effects of these interactions on physical stream habitat—depth, velocity, substrate, cover, and temperature—are a challenge to predict. Improved diagnosis and predictive understanding of future change usually require multifaceted, multi-scale, and multidisciplinary studies based on a firm understanding of the history and processes operating in a drainage basin. The U.S. Geological Survey Federal-State Cooperative Program has been instrumental in fostering studies of the links between land use and stream habitat nationwide.

Circular↗
USGS2019

How physics‐based earthquake simulators might help improve earthquake forecasts

Questions have persisted on the usefulness of physics‐based earthquake simulators with respect to forecasting earthquakes, due mostly to the inevitable assumptions, approximations, and uncertainties. Whether any model is reliable or trustworthy depends entirely on what questions we are asking of it, so the point of this article is to outline a number of currently anticipated and desired inferences, informed largely by recent forecasting efforts in California. This article does not provide an in‐depth review of physics‐based simulators, nor does it render judgment on the usefulness question. The intent, rather, is to provide an explicit list of potential uses, or inferences, to enable more informed discussions among physics‐based modeling experts.

Seismological Research Letters↗
USGS2009

Estimation of fuel conditions for fire danger assessment

A review of physical and chemical properties of fuels relevant for fire ignition and propagation is presented, along with different methods to estimate those properties, with special emphasis on satellite imagery. The discussion is more extended on estimating fuel moisture trends and fuel geometrical properties.

Book chapter↗
USGS1956

Half-life of Th232 and the branching ratio of Bi212

The half-life of Th 232 has been calculated by determining an absolute gamma-disintegration rate for Tl 208 in equilibrium with Th 232 for three old thorium nitrate salts and one natural thorite sample. The branching ratio, α/ ( α + β ) , for Bi 212 , a necessary parameter in the calculation, was also measured. The half-life of Th 232 was found to be 1.42× 10 10 years within an estimated error of 5%, which is essentially in agreement with the presently accepted value. The branching ratio, α/ ( α + β ) , of Bi 212 was found to be 0.362±0.006, about 7.4% higher than the currently accepted value.

Physical Review↗
USGS1960

Magnetic susceptibility of tetragonal titanium dioxide

Careful measurements have been made of the magnetic susceptibility of the rutile and anatase crystalline forms of titanium dioxide. The magnetic susceptibility of a single crystal of high-purity rutile was found to be (0.067±0.0015)× 10 − 6 emu per gram, and was temperature-independent from 55° to 372°K. Difficulty was encountered in obtaining a good value of the magnetic susceptibility of anatase because of impurities. However, a value of 0.02× 10 − 6 emu per gram was obtained as a maximum value for anatase powder. A discussion is given for the different values obtained for anatase and rutile.

Physical Review↗
USGS1968

Van vleck paramagnetism in orthorhombic TiO2 (Brookite)

The magnetic susceptibility of the orthorhombic form of titanium dioxide has been measured from 5 to 300°K. After deducting the temperature-dependent component, which is probably due to defects or impurities, and the free-ion diamagnetic component, the Van Vleck paramagnetism was estimated to be 33× 10 − 6 emu/mole. Comparison is made between this value and the Van Vleck paramagnetism of strontium titanate and the two tetragonal forms of titanium dioxide: rutile and anatase.

Physical Review↗
USGS1954

Thick target bremsstrahlung spectra for 1.00-, 1.25-, and 1.40-Mev electrons

The spectrum of radiation produced by 1.0-, 1.25-, and 1.40-Mev electrons incident on a thick tungsten target was measured at 0° and 90° with the incident beam by a method involving the magnetic analysis of Compton electrons. The effects of electron scattering and energy loss in the target preclude any simple interpretation of this data to yield a differential bremsstrahlung cross section. However, an estimate of the spectra to be expected at 0° and 90° was obtained by combining the Sauter expression for the bremsstrahlung cross section with the available information on electron scatter and energy loss in the target and backscatter from the target. The reliability of the estimate is limited because the Sauter formula was calculated by using the Born approximation, the electron scattering calculations are applicable to an infinite medium only, and the backscatter was estimated empirically from Bothe's experimental data which were obtained with lower energy electrons (370 kev). Furthermore electron energy straggling was neglected. Nevertheless, the predicted spectral shapes at 0° and 90° and the relative intensities at these two angles are in qualitative agreement with the measured values. The absolute magnitudes of the measured intensities at both angles are about a factor of two greater than the predicted values.

Physical Review↗
USGS2023

First observation of the ground-state electron-capture of 40K

Potassium-40 is a widespread, naturally occurring isotope whose radioactivity impacts estimated geological ages spanning billions of years, nuclear structure theory, and subatomic rare-event searches—including those for dark matter and neutrinoless double-beta decay. The decays of this long-lived isotope must be precisely known for its use as a geochronometer, and to account for its presence in low-background experiments. There are several known decay modes for potassium-40, but a predicted electron-capture decay directly to the ground state of argon-40 has never been observed. The existence of this decay mode impacts several fields, while theoretical predictions span an order of magnitude. Here we report on the first, successful observation of this rare decay mode, obtained by the KDK (potassium decay) Collaboration using a novel combination of a low-threshold x-ray detector surrounded by a tonne-scale, high-efficiency γ -ray tagger at Oak Ridge National Laboratory. A blinded analysis reveals a distinctly nonzero ratio of intensities of ground-state electron-captures ( I EC 0 ) over excited-state ones ( I EC ∗ ) of I EC 0 / I EC ∗ = 0.0095 stat ± 0.0022 sys ± 0.0010 (68% CL), with the null hypothesis rejected at 4 σ [Stukel et al. , Phys. Rev. Lett. 131 , 052503 (2023) ]. In terms of branching ratio, this unambiguous signal yields I EC 0 = 0.098 % stat ± 0.023 % sys ± 0.010 % , roughly half of the commonly used prediction. This first observation of a third-forbidden unique electron capture improves our understanding of low-energy backgrounds in dark-matter searches and has implications for nuclear-structure calculations. For example, a shell-model based theoretical estimate for the neutrinoless double-beta decay half-life of calcium-48 is increased by a factor of 7 + 3 − 2 . Our nonzero measurement shifts geochronological ages by up to a percent; implications are illustrated for Earth and solar system chronologies.

Physical Review C↗
USGS1976

Measurements of exclusive photoproduction processes at large values of t and u from 4 to 7.5 GeV

Exclusive photoproduction cross sections have been measured for the processes γ p → π + n , γ p → π 0 p , γ p → π − Δ + + , γ p → ρ 0 p , γ p → K + Λ , and γ p → K + Σ 0 at large t and u values at several energies for each process between 4 and 7.5 GeV. These measurements taken together with past data taken at small values of t and u provide complete angular distributions. The data show the usual small t and u peaks and a central region in which the cross section decreases approximately as s − 7 . The results are discussed within the context of parton or constituent models.

Physical Review D↗
USGS2023

Rare 40K decay with implications for fundamental physics and geochronology

Potassium-40 is a widespread, naturally occurring isotope whose radioactivity impacts subatomic rare-event searches, nuclear structure theory, and estimated geological ages. A predicted electron-capture decay directly to the ground state of argon-40 has never been observed. The KDK (potassium decay) collaboration reports strong evidence of this rare decay mode. A blinded analysis reveals a nonzero ratio of intensities of ground-state electron-captures ( I EC 0 ) over excited-state ones ( I EC ∗ ) of I EC 0 / I EC ∗ = 0.0095 stat ± 0.0022 sys ± 0.0010 (68% C.L.), with the null hypothesis rejected at 4 σ . In terms of branching ratio, this signal yields I EC 0 = 0.098 % stat ± 0.023 % sys ± 0.010 % , roughly half of the commonly used prediction, with consequences for various fields [L. Hariasz et al. , companion paper, Phys. Rev. C 108 , 014327 (2023) ].

Physical Review Letters↗
USGS2004

Two-threshold model for scaling laws of noninteracting snow avalanches

A two-threshold model was proposed for scaling laws of noninteracting snow avalanches. It was found that the sizes of the largest avalanches just preceding the lattice system were power-law distributed. The proposed model reproduced the range of power-law exponents observe for land, rock or snow avalanches, by tuning the maximum value of the ratio of the two failure thresholds. A two-threshold 2D cellular automation was introduced to study the scaling for gravity-driven systems.

Physical Review Letters↗