bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maternal plasma Elabela levels in intrauterine growth restriction
Authors: ALKAN BAYLAN Filiz , KARAKÜÇÜK Selim 
Published: September 2021

Purpose: The aim of this study was to investigate the role of Elabela in the etiopathogenesis of intrauterine growth retardation (IUGR).
Materials and Methods: The present prospective study included 43 healthy pregnant women and 46 pregnant women with IUGR. Maternal serum were collected from the control group and IUGR group at time of delivery. Elabela levels were analyzed in maternal serum through ELISA method.
Results: Lower Elabela levels (IUGR: 1.09 (0.61-15.61) ng / mL and Control: 1.44 (0.37-31.33) ng / mL) were observed in IUGR patients compared to controls. Elabela levels were positively correlated with gestational week and neonatal weight. (r = 0.263, p = 0.013 and r = 0.259, respectively; p = 0.014).
Conclusion: The present study serves as the first study revealing the role of the decrease in Elabela in maternal serum on the etiopathogenesis of IUGR. This suggests that Elabela could be a potential drug target in cases with IUGR.
Modeling path effects in three-dimensional basin structures
Authors: Graves Robert W. , Clayton Robert W. 
Published: September 2021

Abstract
Path effects for seismic wave propagation within three-dimensional (3-D) basin structures are analyzed using a reciprocal source experiment. In this experiment, a numerical simulation is performed in which a point source is excited at a given location and then the wave field is propagated and recorded throughout a 3-D grid of points. Using the principle of reciprocity, source and receiver locations are reversed. This allows the modeling of path effects into a particular observation site for all possible source locations using only one simulation. The numerical technique is based on the use of paraxial extrapolators and currently tracks only acoustic waves. However, the method is capable of handling arbitrary media variations; thus, effects due to focusing, diffraction, and the generation of multiple reflections and refractions are modeled quite well.
The application of this technique to model path effects for local earthquakes recorded at stations in the Los Angeles area of southern California indicates the strong influence of the 3-D crustal basins of this region on the propagation of seismic energy. The modeling results show that the Los Angeles, San Fernando, and San Gabriel basins create strong patterns of focusing and defocusing for paths into these stations from various source locations. These simulations correlate well with earthquake data recorded at both stations. By comparing these calculations with earthquake data, we can begin to evaluate the importance of these basin effects on observed patterns of strong ground motions.
Source parameter estimation for large, bermed, surface chemical explosions
Authors: Reamer Sharon K. , Stump Brian W. 
Published: September 2021

Abstract
Near-source accelerograms (0.2 to 2.0 km range) were acquired from a series of bermed surface charges (0.075 to 1.65 kilotons) detonated in alluvium at a test site near Yuma, Arizona. The areal extent of the explosion test beds (radii from 18 to 54 m) affords the unique opportunity to study wave propagation from and source parameters of large surface explosions at near-source ranges. P and SV-Rayleigh phases are identified using particle motions. Rayleigh waves at an intermediate range transition to a combination of higher mode and fundamental mode Rayleigh waves at the farthest range. The power law decay rates for body waves (radial at r−1.8 and vertical at r−1.4) and surface waves (radial at r−1.0 and vertical at r−0.8) are further indication of complex propagation effects in the shallow alluvial geology. As a result of this complexity and the two-orders-of-magnitude range of explosive yields available, seismic source parameters are obtained with full-waveform spectral ratios. Source corner frequency is proportional to the radius of the explosion test beds and long-period-level (relative moment) scales linearly with yield. Spectral ratio yield estimates using smaller explosions as standard or calibration events gave absolute yield estimates within 6 to 35% of the true yield with a linear scaling law. The precision of individual yield estimates is reflected by multiplicative errors of 1.11 to 1.17. Full-waveform spectral ratio corner frequency estimates compare favorably with reglonal P-wave corner frequencies and validate the use of the spectral ratio technique for near-source seismic data.
A lithospheric velocity anomaly beneath the Shagan river test site. Part 1. Detection and location with network magnitude residuals
Authors: Barker B. W. , Murphy J. R. 
Published: September 2021

Abstract
Large samples of teleseismic P-wave data recorded from Shagan River under-ground explosions have been systematically analyzed in an attempt to understand the causes of mb variability observed for these explosions. Results of these analyses indicate that large (&gt;0.5 magnitude unit) differences in station-corrected mb residuals between explosions in close proximity are associated with changes in the near-source P-wave propagation paths to teleseismic distances. Back projection of the mb residuals from seismic stations in continental Europe into the P-wave initiation area near the source reveals the existence of an anomalous volume of material located about 50 km northwest of the test site, apparently at a depth of about 100 km. This anomalous volume defocuses energy out of paths to certain stations and redirects this energy into the paths to other stations and is associated with no detectable travel-time anomaly. This anomalous volume most likely corresponds to some relatively sharp lateral variation in physical properties, in particular P-wave velocity, at this depth. The estimated lateral dimension of the anomaly is only on the order of 5 km, which would make it one of the smallest deterministic features ever isolated at this depth range.
A two-layer model for aseismic slip on the Superstition Hills fault, California
Authors: Bilham Roger , Behr Jeffrey 
Published: September 2021

Abstract
A new differential creepmeter on the Superstition Hills fault reveals that afterslip at approximately 28 mm/year consists of episodic creep events super-imposed on a slow stable-slip component of 2.4 mm/year. The relative contribution from this background slip (8.5% of the total aseismic surface slip) has remained approximately constant for the past 2 years. To account for this observed behavior, we proposed a two-layer model for aseismic slip in which stable-sliding occurs from the surface to a transition depth, below which episodic creep events are initiated. These creep events propagate to the surface through the stable-sliding layer. From the ratio of background slip velocity to total afterslip velocity, we estimate the ratio of depths of stable-sliding to episodic-slip regions to be approximately 1:10. Thus, assuming that episodic slip extends to 3 km, we infer that background surface creep is moderated by processes in the uppermost 300 m. We speculate that the transition depth is sensitive to applied fault-normal stresses and suggest that the ratio of stable-sliding to episodic-slip velocities may provide an indication of secular variations in tectonic stress. Since the background creep is evidently continuous and little affected by episodic events, its velocity may provide a sensitive indication of applied tectonic strain in the period range days to years.
A survey of blasting activity in the United States
Authors: Richards Paul G. , Anderson Douglas A. , Simpson David W. 
Published: September 2021

Abstract
Statistical information on chemical explosions is needed in seismology, to evaluate the practical difficulties in identifying this very common type of seismic source from other seismic sources such as small earthquakes and small nuclear explosions.
We have obtained data on blasting activity from three different sources: (1) overview information from the U.S. Bureau of Mines (USBM) on the total amount of chemical explosives used in the United States during 1987, with breakdowns into different explosive types, and usage by different states; (2) overview information from the Mine Safety and Health Administration (MSHA) on the numbers of mines, of different types, in the United States; and (3) detailed information from a private company (Vibra-Tech Engineers, Inc.) on total shot size and size of charge per delay for 20,813 blasts carried out in 1987 at 532 locations.
Our procedure has been to extrapolate the detailed information contained in the 1987 Vibra-Tech data for a limited number of states and thus to obtain estimates for the whole country on numbers of shots and their size distribution. The extrapolation is constrained by the data from USBM (numbers of shots, sizes) and the MSHA (locations). Blasting activity does not fluctuate greatly from year to year and 1987 was representative of current practice.
We find that about 2.2 million metric tons of chemical explosive are used annually in the continental U.S., principally in mining for coal and metal ores. On a typical work day, there are roughly 30 explosions greater than 50 tons, including about one greater than 200 tons. There was one industrial explosion in 1987 at about 1400 tons. For shots between 1 ton and 100 tons, the cumulative distribution has a b-value near unity; that is, if N is the number of shots (per year) greater than or equal to W tons,
N ∝ 10 − b log ⁡ W = W − b
with b roughly equal to 1. This result is similar to the size distribution of earthquakes greater than magnitude mb,
N ∝ 10 − b m b .
Almost all chemical explosions above 1 ton are ripple-fired. The typical shot uses 20 to 50 separate delays.
Effects of the canyon topography on ground motions at the Feitsui damsite
Authors: Chiu Hung-Chie , Huang Huey-Chu 
Published: September 2021

Abstract
A numerical scheme based on the boundary integral equation formulation is applied to a two-dimensional SH model of the Feitsui canyon to study the effects of the canyon topography on strong ground motion. The medium responses of this model for plane SH waves incident at various angles were calculated in a frequency band ranging from 0 to 6.0 Hz. It appears that the shielding and scattering effects of canyon topography can greatly modify the ground motions. Based on these medium responses, the recorded SH ground motion at one station is considered as the input to simulate the corresponding component at the second station. The observed and the simulated ground motions at the second station show satisfactory agreement in ground displacement and velocity. The simulated accelerations corresponding to the high-frequency part of ground motions did not fit the observations well. This discrepancy shows the limitation of our simplified model, which does not include the effects of the dam and the variation of topography in the third dimension. In order to improve the simulation of ground accelerations, it is necessary to have the 3-D modeling.
Love-wave propagation in a three-dimensional sedimentary basin
Authors: Toshinawa Takumi , Ohmachi Tatsuo 
Published: September 2021

Abstract
A simplified three-dimensional finite-element method has been developed for simulation of Love-wave propagation in three-dimensional sedimentary basins. The eigenfunctions for the fundamental-mode surface waves are employed as interpolation functions in the finite-element scheme. By reducing the number of degrees of freedom, the method enables us to analyze wave propagation in an area of 2000 km2 as large as the southern part of the Kanto plain, Japan. Time histories of the near Izu-Ohshima earthquake of 1990 are calculated and compared with observation. Calculated displacement snapshots show the effect of three-dimensional topography on direction of Love-wave propagation. The three-dimensional simulation is also compared with a two-dimensional one, demonstrating amplitude increase and extended duration. Time histories and their spectra from the three-dimensional model show better agreement with the observations than those from the two-dimensional model.
P and S-wave displacements from kinematic dislocation models
Authors: Castro R. R. , Anderson J. G. , Brune J. N. 
Published: September 2021

AbstractNumerical dislocation models based on Haskells (1969) formulation are used to estimate the amount of normal motion necessary to produce the high P/S spectral ratios observed from strong-motion records of the Guerrero, Mexico, subduction zone (Castro et al., 1991). While this depends on the nature of the assumed dislocations, a normal motion with amplitude of less than 10% of the amplitude of shear slip is sufficient to produce P/S values comparable with the observations. We model a planar fault with random patches distributed on the fault plane and a nonplanar fault in which a dilatational jog connects en-echelon fault segments (a structural system proposed by Sibson, 1985, 1989, which introduces normal motions on the fault that depend mainly on the geometry of the fault). For the planar fault model the magnitude of the normal motion is prescribed. Both models introduce complexity in both body-wave displacement time histories, although for the P waves this complexity is accentuated at higher frequencies (f &gt; 1 Hz). For the nonplanar model, a jog with an angle of 10° introduces a normal component of 18% of the slip on the fault.
A possible triggering mechanism for large Hawaiian earthquakes derived from analysis of the 26 June 1989 Kilauea south flank sequence
Authors: Bryan Carol J. 
Published: September 2021

Abstract
Examination of short-period seismic data from the ML = 6.1 Kilauea south flank earthquake and aftershock sequence indicates that the rupture process in large Hawaiian earthquakes is more complex than previously modeled. In contrast to the low-angle thrust solution determined for the mainshock from long-period teleseismic body waves by other workers, I find an intermediate- to high-angle reverse solution; I find, however, that focal mechanisms for coastal aftershocks of ML &gt; 3.0 are similar to the teleseismic mechanism for the mainshock.
A difference in focal mechanisms determined from short-period local-network seismic data and from long-period teleseismic data has been noted for other recent large Hawaiian earthquakes. Both the mapping of surface cracks and the focal mechanism derived from short-period seismic data for the ML = 6.6 1983 Kaoiki earthquake show strike-slip motion, whereas the centroid moment tensor solution shows low-angle thrusting. The focal mechanism calculated from short-period seismic data for the ML = 7.2 1975 Kalapana mainshock shows low-angle thrusting according to some workers, but intermediate- to high-angle reverse faulting according to others, whereas focal mechanisms calculated from long-period seismic data show low-angle thrusting.
This result suggests that rupture initiation in large Hawaiian earthquakes, as represented by the short-period focal mechanisms, differs significantly from the overall rupture process, as represented by the teleseismic mechanisms. I propose that small earthquakes trigger the large-scale energy release at the bases of the volcanic edifices, the type of energy release often observed in large Hawaiian earthquakes. These triggering events may occur along rupture surfaces that differ from those along which the long-period moment release occurs and thus may represent release of a local stress concentration superposed upon the regional stress field.
Modeling delay-fired explosion spectra at regional distances
Authors: Chapman M. C. , Bollinger G. A. , Sibol M. S. 
Published: September 2021

AbstractThe objectives of this study are to model the observed seismic spectra from large industrial explosions using information obtained from blaster's logs and to compare the explosion spectra with those of small earthquake signals from the same source region. The data set consists of digital waveforms from four mining explosions (200,000 + lb. of explosives each) and two earthquakes (M = 3.5 and 4.0) in eastern Kentucky. The data were recorded on a short-period regional network at distances ranging from 180 to 400 km and have good signal-to-noise ratios at frequencies from 0.5 to 10 Hz.The explosion amplitude spectra differ markedly from those of the earthquakes, by exhibiting strong time-independent amplitude modulations. This spectral modulation is directly attributable to the explosive charge geometry and firing sequence and is largely independent of source-station path and recording site.Modeling of the explosion source spectra shows that the major contributor to the modulated character of the spectra are amplitude minima at frequencies related to the total duration of the explosion sequence. Another important effect is amplitude reinforcement at low frequencies (e.g., 5 Hz) due to the comparatively long delay (0.2 sec) between the firing of individual rows of explosives. These features dominate both Pg and Lg amplitude spectra at frequencies less than 7 Hz. Accurate modeling of the observed spectra at frequencies greater than a few Hertz requires that the azimuth of the recording site be taken into account. Also, the spectra at higher frequencies become sensitive to random variations in the firing times of any of the various subexplosions.
Peculiarities of surface-wave propagation across central Eurasia
Authors: Levshin Anatoli , Ratnikova Ludmila , Berger Jon 
Published: September 2021

Abstract
The recent installation of six broadband digital IRIS/IDA seismic stations in the USSR has provided new opportunities for studying surface-wave propagation across Eurasia. Group velocities of fundamental Rayleigh and Love modes between epicenters and these stations were determined for 35 events that occurred since April 1989 to the middle of July 1990 near Eurasia. Differential phase velocities were found for the same arrivals along paths between several pairs of stations. Group and phase velocities were obtained in the period range from 15 to 300 sec. Frequency-time polarization analysis was used for studying polarization properties of surface waves. In some cases, significant anomalies in the particle motion for periods up to 100 sec were observed. They are attributed to surface-wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the Eurasia continent.
Three-dimensional model of the Cascadia subduction zone using earthquake hypocenters, western Washington
Authors: Rieken Eric , Thiessen Richard L. 
Published: September 2021

Abstract
The identification of seismically active fault planes is important for assessment of earthquake potential as well as development of neotectonic models and analysis of stress systems for a region. An automated set of computer programs, SEISPLN, has been developed for the identification of three-dimensional (3-D) alignments of seismic hypocenters. The SEISPLN technique is based on rotating a 3-D elongate grid system through the hypocenter distribution. The number of events in each cell is tabulated, and those cells which contain statistically significant numbers of events are considered to be potential fault surfaces. A multiple linear regression is applied to the set of hypocenters in each delineated cell to model the 3-D geometry of each of the inferred fault surfaces. We applied the technique to earthquakes located by the Washington Regional Seismic Network to separate the seismic events associated with the subducted Juan de Fuca (JDF) plate from events in the overlying crust. A total of 259 JDF-associated events were delineated, and the resulting 3-D models of the JDF slab beneath Washington reveal a complex combination of arching and flattening. Also, a steep orientation for the slab is observed beneath the southern portion of the Washington Cascades, while a much shallower orientation is inferred beneath the northern Cascades.
An array study of the effects of a known local scatterer on regional phases
Authors: Gupta I. N. , Lynnes C. S. , Wagner R. A. 
Published: September 2021

Abstract
F-k analyses of NORESS array recordings of teleseismic events have indicated a prominent secondary source about 25 to 30 km southwest of the array, in the region of Lake Mjosa with large topographical relief. Residual seismograms derived by subtracting the beamed record from each array channel are used to investigate the effects of this scatterer on the regional phases Pn, Pg, and Lg from several events at regional distances. The beamed record for each regional phase is obtained by incorporating steering delays based on the known azimuth and phase velocity from the f-k analysis of raw data. Both explosion and earthquake sources along several different azimuths to NORESS provide evidence for scattered arrivals Pn-to-Rg, Pg-to-Rg, and Lg-to-Rg, originating from the same region of Lake Mjosa. These scattered arrivals are observed with remarkable clarity and closeness to the expected arrival times and are rich in low frequencies, as expected for Rg. Their presence in various regional phases indicates that near-receiver scattering plays an important role in the composition of regional phases.
Single-force representation of shallow landslide sources
Authors: Dahlen F. A. 
Published: September 2021

Abstract
A horizontal thrust fault situated at the Earth's surface does not excite any seismic radiation. Because of this and because it provides a satisfactory fit to the data, Kanamori and his co-workers have used a point force rather than a conventional moment tensor to represent the long-period Love- and Rayleigh-wave radiation from a number of shallow landslide sources. The force is supposed by Newton's third law to be ω2MD, where ω is the angular frequency, M is the slide mass, and D is the displacement. Day and McLaughlin (1991) have recently shown that the spall accompanying an underground explosion can be represented either by a shallow horizontal tension crack or by a vertical surface point force ω2MD, where M is the spall mass and D is the crack separation. Using their method, we show that a landslide can be represented in the JWKB approximation either by a shallow double couple or by a horizontal surface point force; for a Love wave the force is FL = ω2MD(1 − β20/c20), whereas for a Rayleigh wave it is FR = ω2MD(1 − 8β20/3c20), where β0 is the shear-wave velocity within the slide mass and c0 is the phase velocity of the surface wave in the vicinity of the source. The sliding block appears to be mechanically decoupled from the rest of the Earth, so that FL ≈ FR ≈ ω2MD, because of the reduced shear velocity β0 within the brecciated rockmass.
Yield estimation using bandpass-filtered seismograms: Preliminary results using neural networks with mb(Pn), short-time, long-time, and coda energy measurements
Authors: Leach Richard R. , Dowla Farid U. , Vergino Eileen S. 
Published: September 2021

Abstract
A neural network has been developed to simultaneously use multiple seismic measurements, such as mb(Pn) and coda energy, for estimating yields of underground nuclear explosions. Yield estimation results based on a large number of Nevada Test Site events that were recorded at the broadband seismic stations at Elko, Kanab, Landers, and Mina indicate that different length windows (6, 18, and 200 sec) of seismogram energy are as useful as the mb(Pn) measurement when the seismogram is filtered between 0.5 and 2 Hz. Detailed results of yield estimation trends as a function of signal frequency are also obtained. Yield estimation performance using long lapse time coda energy above 2 Hz is significantly limited by the signal-to-noise ratio (SNR). Performance of the neural network with both mb(Pn) and energy information as input does not significantly exceed the performance of a conventional linear regression analysis that is based only on mb(Pn). Properties of the coda signal as a function of frequency and SNR that might ultimately lead us to the application of a full seismogram with a neural network for accurate seismic yield estimation are discussed.