bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analysis of seismic and acoustic signals measured from a series of atmospheric and near-surface explosions
Authors: Kitov I. O. , Murphy J. R. , Kusnetsov O. P. , Barker B. W. , Nedoshivin N. I. 
Published: September 2021

Abstract
During December 1985, Soviet scientists monitored a series of high-explosive tests at a bombing range near Kustanai, Kazakhstan, in which both seismic and acoustic data were recorded at distances of 6, 9.5, and 21 km from bomb blasts at different altitudes. These data show a remarkable variety of seismo/acoustic phenomena associated with energy conversion processes at the Earth's surface, including air-coupled Rayleigh waves and acoustic signals produced by propagating seismic disturbances having phase velocities near the speed of sound in air. These data provide valuable new insights into the mechanisms responsible for the generation of seismic and acoustic signals by atmospheric and near-surface explosions. In particular, theoretical simulation results are presented that are shown to account for most of the features of the observed data, and, therefore, it is concluded that the simplified theoretical models employed in these simulations can provide a quantitative basis for assessing the effects of source and site conditions on the characteristics of the signals produced by such explosions.
Topographic site effects. A comparison of two nonreference methods
Authors: Chávez-García Francisco J. , Rodríguez Miguel , Field Edward H. , Hatzfeld Denis 
Published: September 2021

AbstractWe present an experimental study of topographic site effects. The data we use come from an experiment carried out during the summer of 1989, in Epire (northern Greece). Ten digital stations recorded a total of 68 small earthquakes. A recent article (Chávez-García et al., 1996) presented a comparison between site effects determined using horizontal-to-vertical spectral ratios (HVSR) for this data set and theoretical modeling. In this note, we compare the topographic site effects determined using HVSR with another, independent, experimental estimate: a generalized inversion scheme (GIS). Neither HVSR nor GIS depend on the availability of a reference site. We obtain a very good agreement between both estimates of topographic site effects for both horizontal components. Our results support the use of HVSR to determine topographic site effects.
Accuracy analysis of the split-step Fourier propagator: Implications for seismic modeling and migration
Authors: Huang Lian-Jie , Fehler Michael C. 
Published: September 2021

AbstractThe split-step Fourier propagator is a one-way wave propagation method that has been widely used to simulate primary forward and backward (reflected) deterministic/random wave propagation due to its fast computational speed and limited computer memory requirement. The method is useful for rapid modeling of seismic-wave propagation in heterogeneous media where forward scattered waveforms can be considered to be dominant or reverberations can be ignored. The method is based on a solution to the one-way wave equation that requires expanding the square root of an operator and splitting of the resulting noncommutative operators to allow calculation by transferring wave fields between the space and wavenumber domains. Previous analysis of the accuracy of the method has focused on the error related to only a portion of the approximations involved in the propagator. To better understand the accuracy of the propagator, we present a complete formal and numerical accuracy analyses. Our formal analysis indicates that the dominant error of the propagator increases as the first order in the marching interval. We show that nonsymmetrically and symmetrically split-step marching solutions have the same first-order error term. Their second- and third-order error terms are similar. Therefore, the differences between the accuracy of different split-step marching solutions are insignificant. This conclusion is confirmed by our numerical tests. The relation among the phase error of the split-step Fourier propagator, relative velocity perturbation, and propagation angle is numerically studied. The results suggest that the propagator is accurate for up to a 60° propagation angle from the main propagation direction for media with small relative velocity perturbations (10%).
Statistical analysis of irregular wave-guide influences on regional seismic discriminants in China
Authors: Fan Guangwei , Lay Thorne 
Published: September 2021

AbstractShort-period regional phases play an important role in identifying low-magnitude seismic events in the context of monitoring the Comprehensive Test Ban Treaty. Amplitude ratios of regional phases comprised mainly of P-wave energy (Pn, Pg) to those comprised mainly of S-wave energy (Sn, Lg) effectively discriminate between explosions and earthquakes in many regions, particularly at frequencies higher than 3 Hz. At lower frequencies, discrimination is usually poor due to large scatter that causes overlapping of event populations. Scatter in regional discriminant measures such as Pg/Lg ratios is caused by both source and propagation effects, and reducing the scatter imparted by the latter is essential to improving the discriminant performance when events do not share identical paths. Regional phases experience distance-dependent amplitude variations due to effects such as critical angle amplification, geometric spreading, and attenuation. Discriminant measures are usually corrected for empirically determined distance trends for a given region, but large scatter persists after such corrections. This study seeks to develop more sophisticated empirical corrections for path properties in order to further reduce the scatter in regional discriminant measures caused by propagation effects. Broadband seismic waveforms recorded at station WMQ, in western China, demonstrate that regional Pg/Lg ratios show significant distance dependence for frequencies less than 6 Hz. However, variations in crustal structure cause additional path-specific amplitude fluctuations that are not accounted for by regionally averaged distance corrections. Blockage of Lg phases on paths traversing the margins of the Tibetan Plateau is one such effect. Regression analysis demonstrates that Pg/Lg ratios measured at WMQ display significant correlations with path-specific properties such as mean elevation, topographic roughness, basement depth, and crustal thickness. Multiple regressions using optimal combinations of parameters yield corrections that reduce variance in Pg/Lg measurements for frequencies less than 3 Hz by a factor of 2 or more relative to standard distance corrections. This should systematically enhance the performance of the Pg/Lg discriminant at low frequencies. The method presented here can be used for all regions and all short-period regional discriminants. It is likely that the extraordinary crustal heterogeneity in western China represents an extreme case of path-dependent effects.
Seismicity alert probabilities at Parkfield, California, revisited
Authors: Michael Andrew J. , Jones Lucile M. 
Published: September 2021

AbstractFor a decade, the U.S. Geological Survey has used the Parkfield Earthquake Prediction Experiment scenario document to estimate the probability that earthquakes observed on the San Andreas fault near Parkfield will turn out to be foreshocks followed by the expected magnitude 6 mainshocks. During this time, we have learned much about the seismogenic process at Parkfield, about the long-term probability of the Parkfield mainshock, and about the estimation of these types of probabilities. The probabilities for potential foreshocks at Parkfield are reexamined and revised in light of these advances. As part of this process, we have confirmed both the rate of foreshocks before strike-slip earthquakes in the San Andreas physiographic province and the uniform distribution of foreshocks with magnitude proposed by earlier studies. Compared to the earlier assessment, these new estimates of the long-term probability of the Parkfield mainshock are lower, our estimate of the rate of background seismicity is higher, and we find that the assumption that foreshocks at Parkfield occur in a unique way is not statistically significant at the 95% confidence level. While the exact numbers vary depending on the assumptions that are made, the new alert probabilities are lower than previously estimated. Considering the various assumptions and the statistical uncertainties in the input parameters, we also compute a plausible range for the probabilities. The range is large, partly due to the extra knowledge that exists for the Parkfield segment, making us question the usefulness of these numbers.
Faulting along the southern margin of Reelfoot Lake, Tennessee
Authors: Arsdale Roy Van , Purser Jodi , Stephenson William , Odum Jack 
Published: September 2021

Abstract
The Reelfoot Lake basin, Tennessee, is structurally complex and of great interest seismologically because it is located at the junction of two seismicity trends of the New Madrid seismic zone. To better understand the structure at this location, a 7.5-km-long seismic reflection profile was acquired on roads along the southern margin of Reelfoot Lake. The seismic line reveals a westerly dipping basin bounded on the west by the Reelfoot reverse fault zone, the Ridgely right-lateral transpressive fault zone on the east, and the Cottonwood Grove right-lateral strike-slip fault in the middle of the basin. The displacement history of the Reelfoot fault zone appears to be the same as the Ridgely fault zone, thus suggesting that movement on these fault zones has been synchronous, perhaps since the Cretaceous. Since the Reelfoot and Ridgely fault systems are believed responsible for two of the main-shocks of 1811-1812, the fault history revealed in the Reelfoot Lake profile suggests that multiple mainshocks may be typical of the New Madrid seismic zone.
The Ridgely fault zone consists of two northeast-striking faults that lie at the base of and within the Mississippi Valley bluff line. This fault zone has 15 m of post-Eocene, up-to-the-east displacement and appears to locally control the eastern limit of Mississippi River migration. The Cottonwood Grove fault zone passes through the center of the seismic line and has approximately 5 m of up-to-the-east displacement. Correlation of the Cottonwood Grove fault with a possible fault scarp on the floor of Reelfoot Lake and the New Markham fault north of the lake suggests the Cottonwood Grove fault may change to a northerly strike at Reelfoot Lake, thereby linking the northeast-trending zones of seismicity in the New Madrid seismic zone.
Array measurements of phases used in receiver-function calculations: Importance of scattering
Authors: Abers Geoffrey A. 
Published: September 2021

AbstractReceiver-function methods utilize three-component teleseismic P coda to determine structure beneath seismographs. Most methods treat coda complexity as mode conversions and reflections off subhorizontal interfaces beneath the station, such as the Moho. This assumption is evaluated beneath a broadband array in the Kopet Dagh foothills, at Geyokcha, Turkmenistan, by applying array processing techniques to P coda waves at frequencies near 1 Hz. Beneath the Geyokcha array, horizontal components show signals that deviate significantly in slowness and bearing from predictions of a plane-layered Earth. Large phases arrive at the same time as the predicted Ps conversion from the Moho yet systematically come from a single azimuth (from NNE) and travel at phase velocities of 3 to 5 km/sec. The coda waves appear to be P-to-S converted waves from a near-surface scatterer. An inversion for scatterer location is developed and applied to 29 events. Most coda energy comes from a scatterer ∼16 km NNE of the array. This location is coincident with the range-bounding faults that separate Kopet Dagh mountains from adjacent basins. Thus, array analysis shows that signals potentially interpreted as Moho conversions are instead scattered from a near-surface structure. Although these results suggest caution is necessary in interpreting single-station receiver functions, particularly at high frequencies, they also demonstrate the power of array sampling in resolving lateral structure variations.
Three-dimensional simulation of the near-fault ground motion for the 1995 Hyogo-Ken Nanbu (Kobe), Japan, earthquake
Authors: Pitarka Arben , Irikura Kojiro , Iwata Tomotaka , Sekiguchi Haruko 
Published: September 2021

AbstractThe 17 January 1995 Hyogo-ken Nanbu earthquake is a typical example showing that the ground motions along basin-edge faults can be very destructive. In this study, we simulate the near-fault ground motion from this earthquake based on a kinematic fault model and a simplified 3D velocity structure of the Kobe area. The kinematic earthquake rupture and the wave propagation are modeled using a 3D finite-difference method (FDM). Our simulation identifies the basin-edge effect as an important factor that influenced the ground-motion amplification pattern in the Kobe area. We found that the coupling of the source directivity and basin-edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge. The combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin-edge boundary. In some areas, localized site effects might have been as important as the abovementioned effects, but they cannot explain the continuity of the extended east-west zone of damage.
Regionalized versus single-station wave-guide effects on seismic discriminants in western China
Authors: Fan Guangwei , Lay Thorne 
Published: September 2021

AbstractRegional seismic signals play an important role in identifying low-magnitude explosion and earthquake sources for monitoring the Comprehensive Test Ban Treaty (CTBT). To enhance the performance of seismic discriminants, regional phases need to be corrected for propagation effects of large- and intermediate-scale crustal wave-guide heterogeneity. Multivariate regression analysis using parametric path characteristics has shown promise for reducing the propagation-induced scatter in short-period regional phase amplitude ratios. While path length is an important parameter for most seismic phase amplitudes, other parametric features of crustal wave-guide structure are often significantly correlated with regional amplitude ratios of P-wave energy (Pn, Pg) to S-wave energy (Sn, Lg) as demonstrated by our prior work on station WMQ. A question remains as to whether these effects can be regionalized so that they apply to all observations in a given region. We explore the viability of regionalization of wave-guide effects on regional seismic discriminants for frequencies of 0.75 to 6 Hz in central Asia and southwest China by analyzing single- and multi-station data. Linear regressions for single-station data indicate that the significance of specific path parameters extracted from available crustal models varies from one station to another and from one subregion to another. In general, corrections for optimal combinations of wave-guide parameters obtained from multivariate regression reduce the data variance more than conventional corrections for path length alone for both single-station and multi-station data. However, in central Asia, several stations show path dependence on certain variables with opposite signs, so regionalization with multi-station data does not perform well. This is due to highly path-specific effects. In southwest China, there is greater commonality in behavior among stations, and fairly good regionalization can be achieved. However, the resulting variance reduction is still less than that for individual stations because some path effects appear to be direction dependent. Our results indicate that individual station calibration is the preferred procedure, but this should include corrections for path effects beyond simple distance correction.
Nonstationary Bayesian kriging: A predictive technique to generate spatial corrections for seismic detection, location, and identification
Authors: Schultz Craig A. , Myers Stephen C. , Hipp James , Young Christopher J. 
Published: September 2021

AbstractSeismic characterization works to improve the detection, location, and identification of seismic events by correcting for inaccuracies in geophysical models. These inaccuracies are caused by inherent averaging in the model, and, as a result, exact data values cannot be directly recovered at a point in the model. Seismic characterization involves cataloging reference events so that inaccuracies in the model can be mapped at these points and true data values can be retained through a correction. Application of these corrections to a new event requires the accurate prediction of the correction value at a point that is near but not necessarily coincident with the reference events. Given that these reference events can be sparsely distributed geographically, both interpolation and extrapolation of corrections to the new point are required. In this study, we develop a closed-form representation of Bayesian kriging (linear prediction) that incorporates variable spatial damping. The result is a robust nonstationary algorithm for spatially interpolating geophysical corrections. This algorithm extends local trends when data coverage is good and allows for damping (blending) to an a priori background mean when data coverage is poor. Benchmark tests show that the technique gives reliable predictions of the correction value along with an appropriate uncertainty estimate. Tests with travel-time residual data demonstrate that combining variable damping with an azimuthal coverage criterion reduces the large errors that occur with more classical linear prediction techniques, especially when values are extrapolated in poor coverage regions. In the travel-time correction case, this technique generates both seismic corrections along with uncertainties and can properly incorporate model error in the final location estimate. Results favor the applicability of this nonstationary algorithm to other types of seismic corrections such as amplitude and attenuation measures.
Electron-microscopic features of changes in the adrenal and thyroid glands in chronic hypoxia
Authors: Yagubova S. M. 
Published: September 2021

The aimof the studywas to study the characteristic features of ultrastructural changes in the cellular and extracellular matrix of the adrenal and thyroid glands in chronic hypoxia.Materials and methods.The study used the thyroid and adrenal glands of healthy adult male white rats weighing 180-200 g. The anatomical, histological, histochemical, electron microscopic and morphometric methods were used.Results.We found that the response of thyroid and adrenal cells to hypoxia is different. So, since the processes of proliferation in the cells of the thyroid gland occur faster and earlier, all tissues are restored on the 15th day of the experiment in the thyroid gland, and in the adrenal gland are restored only on the 30th day of the experiment. And this can be regarded as a higher degree of sensitivity of the adrenal glands to hypoxia, which is a stronger stress factor than the thyroid gland.Summary.The structures of the thyroid gland adapt to long-term hypoxia earlier, and responds to this with ultrastructural rearrangement – hyperplasia, hypertrophy and proliferation of thyrocytes.
A Single Human-Relevant Fast Food Meal Rapidly Reorganizes Metabolomic and Transcriptomic Signatures in a Gut Microbiota-Dependent Manner#
Authors: Osborn Lucas J. , Orabi Danny , Goudzari Maryam , Sangwan Naseer , Banerjee Rakhee , Brown Amanda L. , Kadam Anagha , Gromovsky Anthony D. , Linga Pranavi , Cresci Gail A. M. , Mak Tytus D. , Willard Belinda B. , Claesen Jan , Brown J. Mark 
Published: September 2021

Abstract

Background:
A major contributor to cardiometabolic disease is caloric excess, often a result of consuming low cost, high calorie fast food. Studies have demonstrated the pivotal role of gut microbes contributing to cardiovascular disease in a diet-dependent manner. Given the central contributions of diet and gut microbiota to cardiometabolic disease, we hypothesized that microbial metabolites originating after fast food consumption can elicit acute metabolic responses in the liver.

Methods:
We gave conventionally raised mice or mice that had their microbiomes depleted with antibiotics a single oral gavage of a liquified fast food meal or liquified control rodent chow meal. After four hours, mice were sacrificed and we used untargeted metabolomics of portal and peripheral blood, 16S rRNA gene sequencing, targeted liver metabolomics, and host liver RNA sequencing to identify novel fast food-derived microbial metabolites and their acute effects on liver function.

Results:
Several candidate microbial metabolites were enriched in portal blood upon fast food feeding, and were essentially absent in antibiotic-treated mice. Strikingly, at four hours post-gavage, fast food consumption resulted in rapid reorganization of the gut microbial community and drastically altered hepatic gene expression. Importantly, diet-driven reshaping of the microbiome and liver transcriptome was dependent on an intact microbial community and not observed in antibiotic ablated animals.

Conclusions:
Collectively, these data suggest a single fast food meal is sufficient to reshape the gut microbial community in mice, yielding a unique signature of food-derived microbial metabolites. Future studies are in progress to determine the contribution of select metabolites to cardiometabolic disease progression and the translational relevance of these animal studies.
Study the Efficiency of Two Concentrations from Algae Cladophora glomerata Extract on the Giardia lamblia parasite
Authors: Fayyad Raghad J. , Lefta Siham N. , Mohammed Dina Yousif , Maliki Sara A.J. 
Published: September 2021

Giardia lamblia parasite was isolated from the diarrhea samples of patients with Giardiasis dysentery and was developed in HSP media, four mice groups have been used to find in vivo efficacy of two concentrations (128,256) mg/ml of chlorophorm extracts from Cladophora glomerata algae against Giardia lamblia parasite as compared with (Flagyl) by measuring several biochemical markers as ( GPT and GOT) enzymes ,sodium ,potassium and iron concentration as well as counting the number of parasitic cysts in each mice groups. The results demonstrate that levels of GPTA GOT enzymes have been decreased in mice treated with algal extract. As for the concentration of the Sodium, Potassium and Iron increased in mice treated with algal extract. The number of the Giardia cyst is also reduced in orally inoculated mice with both concentrations of algal extract as compared with positive control and the Flagyl treated group. In terms of bioactive compounds, GC-Mass results indicate the presence of many phytochemicals with different biologically active properties This study represents the first attempt to use Cladophora glomerata derived from phytochemicals to treat giardiasis in vivo.
Numerical Solutions of Two-Dimensional Vorticity Transport Equation Using Crank-Nicolson Method
Authors: Rasheed Maan A. , Kadhim Suad Naji 
Published: September 2021

This paper is concerned with the numerical solutions of the vorticity transport equation (VTE) in two-dimensional space with homogenous Dirichlet boundary conditions. Namely, for this problem, the Crank-Nicolson finite difference equation is derived. In addition, the consistency and stability of the Crank-Nicolson method are studied. Moreover, a numerical experiment is considered to study the convergence of the Crank-Nicolson scheme and to visualize the discrete graphs for the vorticity and stream functions. The analytical result shows that the proposed scheme is consistent, whereas the numerical results show that the solutions are stable with small space-steps and at any time levels.