bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for prehistoric earthquakes on the Superstition Hills fault from offset geomorphic features
Authors: Lindvall Scott C. , Rockwell Thomas K. , Hudnut Kenneth W. 
Published: July 2021

Abstract
Offset geomorphic features along the Superstition Hills fault show evidence for at least one slip event prior to the 1987 surface rupture, and possibly as many as four to five earlier prehistoric earthquakes. We documented several geomorphic features that appeared offset by multiple events by making detailed topographic maps. Offset features were abundant along reaches of the fault with high topographic relief and large displacement. Slip distribution for the penultimate event, as recorded by offset rills, streams, and shrub-coppice dunes, is very similar to the slip distribution from the 1987 earthquake through April 1988. This similarity may prove to be fortuitous if afterslip from the 1987 event continues to increase the total slip for this earthquake. But if afterslip associated with the 1987 event ceases in the near future, then the past two earthquakes were nearly identical in slip, and the Superstition Hills fault may be expected to produce characteristic earthquakes of roughly magnitude 612.
Moment-tensor solutions for the 24 November 1987 Superstition Hills, California, earthquakes
Authors: Sipkin Stuart A. 
Published: July 2021

Abstract
The teleseismic long-period waveforms recorded by the Global Digital Seismograph Network from the two largest Superstition Hills earthquakes are inverted using an algorithm based on optimal filter theory. These solutions differ slightly from those published in the Preliminary Determination of Epicenters Monthly Listing because a somewhat different, improved data set was used in the inversions and a time-dependent moment-tensor algorithm was used to investigate the complexity of the main shock. The foreshock (origin time 01:54:14.5, mb 5.7, Ms 6.2) had a scalar moment of 2.3 × 1025 dyne-cm, a depth of 8 km, and a mechanism of strike 217°, dip 79°, rake 4°. The main shock (origin time 13:15:56.4, mb 6.0, Ms 6.6) was a complex event, consisting of at least two subevents, with a combined scalar moment of 1.0 × 1026 dyne-cm, a depth of 10 km, and a mechanism of strike 303°, dip 89°, rake −180°.
Scattering of long-period Rayleigh waves in Western North America and the interpretation of codaQmeasurements
Authors: Langston Charles A. 
Published: July 2021

AbstractThe codas of long-period Rayleigh waves recorded at WWSSN and Canadian network stations in Western North America from eight underground explosions at NTS are examined in an effort to separate scattering and anelastic attenuation effects. Coda behavior of 0.1 and 0.2 hz Rayleigh waves follows coda characteristics seen in studies of short-period S waves. Coda decay rate is seen to be a stable observation over most stations in Western North America and is consistent with the hypothesis that backscattered surface waves from heterogeneities contained within the western half of the continent form the Rayleigh wave coda. The basic data observables of coda level and decay are interpreted using several plausible models. The single scattering model yields a coda Q consistent with previously determined Rayleigh anelastic attenuation coefficients. Separation of anelastic and scattering Q is possible using an energy flux model and shows that scattering Q is one to two orders of magnitude higher than anelastic Q. However, an energy flux model that incorporates a layer of scatterers over a homogeneous half-space shows that all Rayleigh-wave attenuation can be explained purely by scattering effects which include Rayleigh- to body-wave conversion. Coda can be fit equally well by these mutually incompatible models. It is not likely that the mechanisms of scattering or anelastic attenuation can be addressed by coda observations of a single homogeneous data set.
An algorithm for automated tsunami warning in French Polynesia based on mantle magnitudes
Authors: Talandier Jacques , Okal Emile A. 
Published: July 2021

AbstractWe have developed a new magnitude scale, Mm, based on the measurement of mantle Rayleigh-wave energy in the 50 to 300 sec period range, and directly related to the seismic moment through Mm = log10M0 − 20. Measurements are taken on the first passage of Rayleigh waves, recorded on-scale on broadband instruments with adequate dynamical range. This allows estimation of the moment of an event within minutes of the arrival of the Rayleigh wave, and with a standard deviation of ±0.2 magnitude units. In turn, the knowledge of the seismic moment allows computation of an estimate of the high-seas amplitude of a range of expectable tsunami heights. The latter, combined with complementary data from T-wave duration and historical references, have been integrated into an automated procedure of tsunami warning by the Centre Polynésien de Prévention des Tsunamis (CPPT), in Papeete, Tahiti.
Phase velocity estimation of diffusely scattered waves
Authors: Dainty Anton M. , Harris David B. 
Published: July 2021

AbstractTwo methods are investigated for estimating the phase velocity of diffusely scattered seismic waves simultaneously arriving from different azimuths and recorded by a two-dimensional array of seismometers. The Hankel spectrum is the average of the frequency-wavenumber (FK) spectrum over all azimuths, while the wavenumber spectrum is derived by integrating the FK spectrum around a contour of constant phase velocity, i.e., a circle centered on the origin in the wavenumber plane. If the conventional estimate of the FK spectrum using the covariance matrix of the seismometer signals is integrated, a closed form for both the Hankel spectrum and the wavenumber spectrum may be found; the two spectra are very similar, the wavenumber spectrum being equal to the Hankel spectrum times the wavenumber. In spite of this similarity, however, we find that the two formulations have significantly different behavior for small wavenumbers, i.e., high phase velocities. In both cases there is a highest (true) velocity that can be estimated from the spectral maximum for a given array aperture (“velocity cut-off”). The Hankel spectrum estimates too high a velocity; for true wavenumbers below a certain limit, infinite velocity is estimated. The wavenumber spectrum, on the other hand, estimates too low a velocity, and there is an upper limit on the estimated velocity. An example illustrating these difficulties for the two methods is given for teleseismic P coda of an event recorded at the NORESS array in southern Norway: in spite of the problems, the analysis is able to demonstrate that the coda consists of two components; a coherent P-wave component with a high phase velocity and a diffuse S-wave component of low phase velocity. The cut-off and bias problem are investigated by numerical simulation for the NORESS array using azimuthal averaging and synthetic signals. The results confirm and quantify the cut-off problem at low wavenumbers and indicate that wavenumbers estimated from the Hankel and wavenumber spectra maxima bracket the true wavenumber, with the Hankel spectrum estimate being low (phase velocity too high) and the wavenumber spectrum estimate high. The bias of both methods decreases with increasing wavenumber (decreasing phase velocity) and they are both asymptotically unbiased. The wavenumber spectrum has a superior performance at low wavenumbers (high phase velocity), but the Hankel spectrum gives superior results at high wavenumbers (low phase velocity). The product of the linear wavenumber (= 1/wavelength) and the array aperture define “high” and “low” wavenumbers; for low wavenumbers, the product is 1 or less. In an Appendix, we find absolute lower bounds on the cut-offs analytically. The problems could be mitigated by using high resolution methods.
Foam rubber modeling of topographic and Dam interaction effects at Pacoima Dam
Authors: Anooshehpoor Abdolrasool , Brune James N. 
Published: July 2021

AbstractA study of the topographic and dam interaction effects was made using a 3-D foam rubber model of the actual topography around the Pacoima Dam accelerograph which recorded over 1 g high-frequency horizontal ground accelerations during the 1971 San Fernando earthquake. Scaling of frequency from the model to the earth depends on the average value of shear-wave velocity in the upper few hundred meters. Assuming βe = 2 km/sec, for vertically incident SH waves, the spectral ratio of the ground acceleration on the ridge to the free field (flat surface) indicates an amplification of about 60 per cent around 6.5 Hz on the N76°W component. Topography has little effect upon the motion recorded on the S14°W component. Motion on the ridge is lower than the free-field motion on both horizontal components for frequencies above 9 Hz. Amplification peaks shift to higher or lower frequencies depending on the assumed shear-wave velocity in the upper few hundred meters.Results from nonvertically incident SH waves show that the topographic effect is dependent on the direction of approach of the seismic energy. The effect is either de-amplification (in part by shadowing) or amplification (relative to the case where no topography is present), depending on whether the canyon is on the ray path or not. The Fourier spectrum of the ground motion at the dam crest shows peak frequencies at about 5 Hz and 10 Hz (resonance), which correspond to the normal modes of the dam. A study of dynamic interaction between the Pacoima Dam and the ridge shows that the coupling is less than 2 per cent at about 10 Hz and less than 12 percent at about 5 Hz.
A stability checking procedure for finite-difference schemes with boundary conditions in acoustic media
Authors: Kamel Aladin H. 
Published: July 2021

AbstractThe manner in which boundary conditions are approximated and introduced into finite-difference schemes has an important influence on the stability and accuracy of the results. The standard von Neumann stability condition applies only for points which are not in the vicinity of the boundaries. This stability condition does not take into consideration the effects caused by introducing the boundary conditions to the scheme. In this paper, we extend the von Neumann condition to include boundary conditions. The method is based on studying the time propagating matrix which governs the space-time behavior of the numerical grid. Examples of applying the procedure on schemes with different boundary conditions are given.
A versatile equalization circuit for increasing seismometer velocity response below the natural frequency
Authors: Roberts Peter M. 
Published: July 2021

AbstractA versatile and easily implemented circuit is described that increases the velocity amplitude response of seismometers below their natural frequency in order to extend the useful bandwidth to lower frequencies. The circuit employs a simple design that counteracts the Ï‰2 rolloff of the seismometer by cascading two one-pole active low-pass filters in series. The low-pass stages are each summed with the unfiltered signal to maintain a flat unity amplitude response near and above the natural frequency. The design, testing, and field implementation are described for a version of the circuit used with Mark Products L4-C 1.0 Hz seismometers. The design produced a nominally flat response extending down to 0.1 Hz with tolerable stability over a wide range of ambient temperatures. Design procedures are described so that the circuit may be easily modified for any arbitrary natural frequency and range of desired equalization. The circuit can be installed very easily in nearly any recording equipment with minimal modification of existing circuitry. An example is shown of the measured and theoretical amplitude and phase responses for an existing seismic event recorder with and without the equalization circuit installed. The agreement between the measured and theoretical responses is excellent for both of these instruments configurations.
Seismic calibration using the simplex algorithm
Authors: Steck Lee , Prothero William A. 
Published: July 2021

AbstractWe have modified the software of Sauter and Dorman (1986) to produce a robust and flexible calibration program that works in the frequency domain for longer and noisy calibration signals, as well as in the time domain when shorter, high signal-to-noise calibration signals may be used. The most important improvement was to replace the least squares fitting of the complex polynomial representation of the response function with the simplex fitting of the pole-zero representation of the response function. The simplex algorithm always converges to a minimum, regardless of starting model, and by fitting the poles and zeroes directly, we minimize the degrees of freedom of the solution. Typical VAX 11/750 CPU requirements are on the order of 2 to 3 minutes for both codes, with average errors less than 1 per cent in amplitude and 1° in phase.
Destructive strong ground motion in Mexico city: Source, path, and site effects during great 1985 Michoacán earthquake
Authors: Campillo M. , Gariel J. C. , Aki K. , Sánchez-Sesma F. J. 
Published: July 2021

AbstractSimultaneous consideration of source, path, and site effects on ground motion during the Michoacán earthquake of 1985 allows us to draw coherent conclusions regarding the roles played for the disaster in Mexico City by the rupture process, the mode of propagation of the waves between the epicentral zone and Mexico City, and the local amplification. In contrast to the horizontal component which showed dramatic amplification for the 2 to 3 sec motion at lake sediment sites, we observe almost identical vertical displacement seismograms containing ripples with 2 to 3 sec period throughout the Mexico City valley whether the recording site is on the lake sediments or on hard rock. We, therefore, conclude that the 2 to 3 sec motion responsible for the destruction of Mexico City was present in the incident field. After performing a phase analysis, we interpret the signal as the superposition of long-period Rayleigh waves and short-period Lg with a dominant period of about 3 sec. The analysis of the teleseismic records indicates that the radiation of this event is enhanced for waves around the 3 sec period. Except in the case of stations for which an anomalous path effect is suspected, the records present ripples appearing a few seconds after the beginning of the signal. The characteristics of near-fault records show that the rupture process consists of the growth of a smooth crack. The numerical simulation indicates that the 3 sec period ripples can be explained by a series of changes of the rupture front velocity. We examine two alternative source models associated with different crustal models to explain the characteristics of the vertical displacements recorded in Mexico City. Our preferred model attributes the cause of the enhanced 3 sec motion to the irregularity in the rupture propagation in addition to the effect of the local conditions in Mexico City. This interpretation leads to a very coherent scenario of what happened from the start of the failure on the fault up to the destruction in Mexico City. This example illustrates the need to consider simultaneously source, path, and site effects in order to understand strong ground motions.
Crustal structure in the southern Bering Shelf and the Alaska Peninsula from inversion of surface-wave dispersion data
Authors: Niazi Mansour , Chun Kin-Yip 
Published: July 2021

AbstractDispersion of surface waves in the southern Bering Shelf (Bristol Bay) and the Alaska Peninsula is investigated for a study of the regional crustal structure. Our data consist of five shallow earthquakes located along the Aleutian Arc and recorded by long-period, three-component seismographs sited in south-central Alaska. Both Love and Rayleigh group velocities are obtained through the application of the phase-matched filtering technique. The results are converted to equivalent pure-path data by appropriate adjustment using the published information for the continental Alaska.Treating the shear velocity of each layer as an independent parameter, the pure-path group velocities of Love and Rayleigh waves are jointly inverted in order to obtain a satisfactory agreement between the theoretical and the observed dispersion characteristics. Estimates of the resolving power of the inversion and uncertainty of the final velocity structure show substantial improvement over the previously published models.With their crustal thicknesses ranging between 33 and 36 km, none of the final models displays structural characteristics reminiscent of an oceanic crust. Over the northernmost path across the Bristol Bay, we found an indication of a weak low-velocity zone (five per cent reduction relative to the lid velocity) whose prominence diminishes towards the south.
Evaluation of Anticholinergic, Antidiabetic and Antioxidant Activity of Astragalus dumanii, an Endemic Plant
Authors: KOÇYİĞİT Ümit Muhammet , ERUYGUR Nuraniye , ATAŞ Mehmet , TEKİN Mehmet , TASLİMİ Parham , GÖKALP Faik , GÜLÇİN İlhami 
Published: July 2021

The research was conducted to separately evaluate and detect the possible in vitro antioxidant, antimicrobial activity of ethanol extracts prepared from aerial parts and roots of Astragalus	dumanii and anti-cholinesterase and α-glucosidase inhibitory activity from only aerial parts of its The antioxidant capacity was tested by scavenging of DPPH and ABTS free radicals. Compared with the standard antioxidant compound gallic acid; Root and aerial part extract showed lower DPPH radical scavenging activity, however aerial part extract demonstrated higher ABTS radical scavenging activity. The phenolic contents were detected as 5.31 ± 0.03 and 13.23 ± 0.05 mg gallic acid equivalent g-1 extract, flavonoid contents were found as 8.26 ± 0.004 and 7.93 ± 0.005 mg Qercetin equivalent g-1 extract. In addition, the effects of the extracts obtained from aerial parts of the plant on acetylcholinesterase, butyrylcholinesterase and a-glycosidase enzymes were investigated in vitro and IC50 values were obtained as 1.47, 0.83 and 0.48 µg mL-1, respectively. When these values were compared with standard substances, it was seen that Astragalus dumanii could be a good enzyme inhibitory agent. Antimicrobial activity of the plant extracts were determined using the microdilution method and the extracts was not observed to have any antimicrobial activities..
Пропозиції зі скорочення енерговитрат у локомотивному депо
Authors: Крашенінін О.С. , Одєгов М.М. , Березняк М.К. , Пивовар Д.І. 
Published: July 2021

Енергетичне господарство локомотивного депо займає суттєву частку витрат на організацію функціонування інших господарств депо і локомотивного парку. В умовах подорожчання цін на енергоресурси перед локомотивним господарством депо постають актуальні завдання розроблення комплексу заходів щодо запровадження стратегії економії енерговитрат.
У статті аналізується динаміка технічного стану локомотивного парку і динаміка енерговитрат депо за кілька років. Зважаючи на це, намічено конкретні пропозиції з економії енерговитрат у локомотивному депо
INFLUENCE OF VAPOR AND CRYSTAL FORMATION PROCESSES ON HEAT EXCHANGE IN FILM VAPORATORS
Authors: Koshelnik O. , Pavlova V. , Pugacheva T. , Kruglyakova O. , Dolobovska O. 
Published: July 2021

Evaporators for changing the concentration of solutions have a different design, depending on the type of processed substance.
Significant energy consumption in such equipment is associated with the need for removing large quantity of liquid phase.
Multiple-effect evaporators are used to reduce the energy consumption of the evaporation process, but such equipment is quite expensive.
Evaporators with secondary vapor heat reusing that operate in film mode can be an alternative to multi-effect evaporators. This equipment can operate efficiently across minimal temperature differences due to secondary vapor compressors. The disadvantage of this device is strict requirements for impurities in solutions.
Impurities create deposits (incrustations) of various substances on the heat transfer surfaces, which worsens the operating conditions.
If crystallizing solutions are used in evaporators with reusing of secondary vapor heat, then one of the ways to reduce the rate of heating surfaces incrustation is to add a solid phase to the initial solution.
A mathematical model is proposed to describe the processes of heat and mass transfer during the film flow of crystallizing solutions, which are accompanied by a change in the physical characteristics of the solution and the formation of deposits.
The model considers a three-phase liquid suspension with a varying phase content. Two stages of vaporization including vaporization on the surface of the liquid and on the surface of heat exchange are presented.
The mathematical model involves the equations of continuity, energy and heat transfer, as well as the equations of motion of a three-phase flow with a changing phase content for both stages of vaporization, taking into account that solid phase turbulizes the flow and intensifies the heat transfer process.
This mathematical model makes it possible to study the effect of the solid phase on heat transfer processes and the rate of incrustation in evaporators with reuse of secondary vapor heat.