bluuebunny/crossref_metadata_2025_split huggingface dataset:
Velocity contrast across the San Andreas fault in central California: Small-scale variations from P-wave nodal plane distortion
Authors: McNally Karen C. , McEvilly Thomas V. 
Published: September 2021

abstract
Systematic variations in P-wave radiation patterns, evident in a data set of 400 central California earthquakes, have been analyzed for variations in velocity contrast across the San Andreas fault zone. Vertical strike-slip faulting characterizes the region, with radiation patterns well constrained by the dense local seismographic station network. A discontinuity in crustal velocity occurs across the San Andreas fault. The distribution of systematically inconsistent first motions indicates that first arrivals observed along the fault plane within the northeastern block have followed refracted paths through the higher velocity crustal rocks to the southwest, retaining P-wave polarities characteristic of the quadrant of origin, and thus appearing reversed. A simple geometrical interpretation, with P waves refracted at the fault plane near the focus, yields the velocity contrast across the fault zone; the distribution of hypocenters allows its mapping in time and space. The velocity contrast so determined ranges up to 15 per cent, for a depth range of 1 to 10 km. The observed pattern of contrast values is coherent, with the greatest contrast related apparently in space, and possibly in time, to the larger earthquakes occurring on the fault. We suggest the phenomenon reflects changes in stress state at the fault and, by virtue of its ease of measurement, offers a new and valuable technique in earthquake studies.
A macroseismic study and the implications of structural damage of two recent major earthquakes in the Jordan Rift
Authors: Vered M. , Striem H. L. 
Published: September 2021

abstract
A detailed macroseismic study of the July 11, 1927 earthquake was carried out. A quantitative analysis of damage data provided a correlation for estimating (MM) intensities: I = 6.4 + 1.2 log (percentage of damaged houses). Using axis lengths and areas bounded by the ensuing isoseismal lines, the depth (16 to 28 km) of the event was estimated, and its probable epicenter located near Damiya bridge on the Jordan river. A comparison with the equivalent parameters, inferred from instrumental records, shows agreement between both sets of results and thus confirms the validity of the approach used in the macroseismic study.
The same procedure of studying macroseismic data was applied to an earlier (January 1, 1837) destructive earthquake. It was found that this latter event orginated in the upper crust, eastward of Safed, with a 6.25 to 6.5 magnitude.
The isoseismals of both these major earthquakes are elongated in a north-south direction, along the major structural trend in the area. The southern coastal plain of Israel seems generally less vulnerable to Jordan Rift Valley earthquakes than inland regions of similar epicentral distances, though local pockets of anomalous intensities are observed for both earthquakes.
Dislocation modeling of creep-related tilt changes
Authors: McHugh Stuart , Johnston Malcolm J. S. 
Published: September 2021

abstract
Tilt changes associated with 1 to 5 mm of fault creep have been detected at several different locations on the San Andreas fault on tiltmeters within 500 meters of the creep observation point. The creep-related tilts have amplitudes of ≲0.5 μrad and durations comparable to the creep events. No changes ≳10-2 μrad have been observed on tiltmeters at distances ≳1 km from the fault at the time of the creep events. Dislocation models capable of replicating the creep-related tilt events have been constructed to examine the relationship of the model parameters to details of the tilt wave forms. The tilt time histories, source-station configuration, and the displacement time history can be used to infer the type and amount of the displacement, the propagation direction and depth of the slip zone. The shallow depth and finite size of the slip zone indicated by these models contrasts with the horizontal extent over which many creep observations occur. Slip of longer duration and larger extent at depths below a few kilometers that loads the surface material to failure could explain these observations.
Earthquake modeling in a homogeneous half-space
Authors: Hartzell Stephen H. , Frazier Gerald A. , Brune James N. 
Published: September 2021

Abstract
Ground motion produced by finite, kinematic fault surface is modeled at the surface of a homogeneous half-space. The Green's functions for point dislocations are summed to investigate the effects of different rupture velocities and source rise times. Displacements and velocities are compared for a bilateral and unilateral rupture. The method is used to model the displacements for a laboratory experiment involving a dynamic rupture in a homogeneous block of foam rubber. Good agreement between synthetic and model displacements is obtained at distances ranging from zero to somewhat greater than one fault length. The half-space Green's function summation method is then used to model the N65°E (transverse) component of displacement for the 1966 Parkfield earthquake. The 26-cm displacement pulse on this record is fit with a buried dislocation of 100 cm over a rectangular fault 30 km long and 6 km wide, with a depth of 3 km.
A seismological study of two Attica, New York earthquakes
Authors: Herrmann Robert B. 
Published: September 2021

abstract
The Attica, New York earthquakes of January 1, 1966 and June 12, 1967 are studied in detail to obtain their focal mechanisms, depths and seismic moments. Both events have similar source parameters with one nodal plane striking about 120° and dipping 60°S and the other nodal plane striking about 20° and dipping 70°E. The fault motion on the NNE nodal plane has a component of right lateral strike slip and one of reverse faulting. Though this nodal plane parallels the Clarendon-Linden structure, the possibility of associating the other nodal plane with a diffuse east-west seismicity trend cannot be excluded. The shallow focal depth of 2 to 3 km for these two events can be used as an explanation of the relatively high epicentral intensity VIII of the Attica event of 1929.
Strong-motion accelerograms of the Oroville aftershocks and peak acceleration data
Authors: Seekins Linda C. , Hanks Thomas C. 
Published: September 2021

abstract
In the 90 days following the Oroville, California, earthquake (August 1, 1975; ML = 5.7), 313 positively identified strong-motion accelerograms were obtained for 86 different aftershocks. This set of records samples a wide range of magnitude (1.8 ≦ ML ≦ 5.2), focal depth (2 ≦ h ≦ 12 km), and site conditions (Holocene alluvium to Mesozoic crystalline basement). Most of these records were written at hypocentral distances R ≦ 15 km, a distance range for which relatively few strong-motion accelerograms had previously been available. Equally significant is the completeness of coverage (seven or more positively identified records) available for each of 12 well-recorded aftershocks (2.8 ≦ ML ≦ 4.9). One hundred and sixty-five peak acceleration values at 6.7 ≦ R ≦ 15 km for 33 aftershocks (3.0 ≦ ML ≦ 4.9) are the basis of an investigation of the dependence of peak acceleration on magnitude at R ≃ 10 km. These observations are supplemented with one datum for the main shock, 6 observations for two ML ≧ 5 aftershocks, and 61 null observations. Peak accelerations at sites on bedrock or minor sedimentary thicknesses are consistently higher than those at sites on several hundred meters or more of sedimentary rocks. Mean values for both site classes of data increase fairly rapidly with magnitude for 3 ≦ ML &lt; 5, but the little available data for ML ≧ 5 suggest this magnitude dependence abruptly terminates at ML ≃ 5. The magnitude dependence of the sedimentarysite data is apparently stronger than for the bedrock-site data. Much if not all of the apparent magnitude dependence of these data can be attributed to properties of the path and not the source, consistent with the hypothesis that the amplitude of the peak acceleration phase, as it leaves the source region, does not depend on source strength although the predominant frequency of this phase increases as the duration and magnitude of the earthquake decreases.
Microtremor site analysis study at Beatty, Nevada
Authors: Katz Lewis J. , Bellon Robert S. 
Published: September 2021

abstract
Current microzonation mapping procedures often call for the generation of complicated mathematical ground-motion models. These models require that expensive geophysical and geological surveys be performed to gather input information. A more desirable method of estimating ground motions would be to measure these effects directly. Microtremor analysis procedures provide such a direct method. Microtremor data were collected at several sites at Beatty, Nevada, and compared to nuclear event and mathematical model ground-motion spectra. The frequency at which peak amplitudes occurred on all spectra agreed. These frequencies appear at the resonance frequency of the surface layer when stimulated by compressional waves. Results of this experiment add validity to the use of microtremors in microzonation studies.
The effect of soil-structure interaction on seismometer readings
Authors: Bycroft G. N. 
Published: September 2021

abstract
Rocking and vertical and horizontal translations of typical “free-field” seismometer installations lead to magnification of the ground motion record. This magnification can be significant for the higher frequency components if the terrain has a relatively low shear-wave velocity. Seismometers placed on foundations which cover a significant part of a wavelength of a horizontally incident wave, experience an attenuated ground motion. A method of correcting the seismograms for these effects is given. Compliance functions for a rigid sphere in a full elastic space are derived and are used to show that, in practical cases, down-hole seismometer installations are not significantly affected by interaction. These compliance functions should be useful in discussing the soil structure interaction of structures erected on bulbous piles. They may be also used as the basis of a method of determining elastic constants of ground at depth, in situ, and at different frequencies.
Shear-wave travel times and amplitudes for two well-constrained earthquakes
Authors: Hart Robert S. , Butler Rhett 
Published: September 2021

abstract
The wave-form correlation technique (Hart, 1975) for determining precise teleseismic shear-wave travel times is extended to two large earthquakes with well-constrained source mechanisms, the 1968 Borrego Mountain, California earthquake and the 1973 Hawaii earthquake. A total of 87 SH travel times in the distance range of 30° to 92° were obtained through analysis of WWSSN and Canadian Network seismograms from these two events. Major features of the travel-time data include a trend toward faster travel times at a distance of about 40° (previously noted by Ibrahim and Nuttli, 1967; Hart, 1975); another somewhat less pronounced trend toward faster times at about 75°; a +6 sec base line shift, with respect to the Jeffreys-Bullen Table, for the Borrego Mountain data; and large azimuthally-dependent scatter for the Hawaiian data, probably reflecting dramatic lateral variations in the near-source region. When azimuthal variations in the Hawaii data are removed, the travel times from both events show very low scatter. The correlations were also used to investigate SH amplitudes for possible distance dependence in the data and variations in tβ*. The Borrego Mountain data show very low scatter and no discernible distance dependence. All of the data are compatible with a value of tβ* = 5.2 ± 0.5. The amplitudes from the Hawaii earthquake show the same azimuthal variations found in the travel-time data. When those effects are removed, the Hawaii data satisfies a value of tβ* equal to 4.0 ± 0.5 and, as with the other data set, no distance dependence is apparent.
The effects of boundary friction on the propagation of elastic waves
Authors: Miller Richard K. 
Published: September 2021

abstract
The effects of a frictional boundary plane on the propagation of normally incident plane harmonic shear waves is investigated by an approximate analytical technique. Three nonlinear models for sliding boundary friction are considered, including a new model which accounts for kinematic locking effects at large slip displacements. It is shown that maximum energy absorption at the boundary occurs in each case for an intermediate level of boundary friction.
Duration of nuclear explosion ground motion
Authors: Hays Walter W. , King Kenneth W. , Park Robert B. 
Published: September 2021

abstract
This paper evaluates the duration of strong ground shaking that results from nuclear explosions and identifies some of the problems associated with its determination. Knowledge of the duration of horizontal ground shaking is important out to epicentral distances of about 44 km and 135 km, the approximate distances at which the ground shaking level falls to 0.01 g for nuclear explosions having yields of about 100 kt and 1,000 kt, respectively. Evaluation of the strong ground motions recorded from the event STRAIT (ML = 5.6) on a linear array of five, broad-band velocity seismographs deployed in the distance range 3.2 to 19.5 km provides information about the characteristics of the duration of ground shaking. The STRAIT data show that: (1) the definition that is used for defining duration is very important; (2) the duration of ground acceleration, as defined in terms of 90 per cent of the integral of the squared time history (Trifunac and Brady, 1975), increased from about 4 to 26 sec over the approximately 20-km distance range; and (3) the duration of ground velocity and displacement were slightly greater because of the effect of the alluvium layer on the propagating surface waves. Data from other events (e.g., MILROW, CANNIKIN, HANDLEY, PURSE) augment the STRAIT data and show that: (1) duration of shaking is increased by frequency-dependent site effects and (2) duration of shaking, as defined by the integral of the squared time history, does not increase as rapidly with increase in yield as is indicated by other definitions of duration that are stated in terms of an amplitude threshold (e.g., bracketed duration, response envelopes). The available data suggest that the duration of ground acceleration, based on the integral definition, varies from about 4 to 40 sec for a 100-kt range explosion and from about 4 to 105 sec for a megaton range explosion in the epicentral distance range of 0 to 44 km and 0 to 135 km, respectively.
The source mechanism of the August 7, 1966 El Golfo earthquake
Authors: Ebel John E. , Burdick L. J. , Stewart Gordon S. 
Published: September 2021

abstract
The El Golfo earthquake of August 7, 1966 (mb = 6.3, MS = 6.3) occurred near the mouth of the Colorado River at the northern end of the Gulf of California. Synthetic seismograms for this event were computed for both the body waves and the surface waves to determine the source parameters of the earthquake. The body-wave model indicated the source was a right lateral, strike-slip source with a depth of 10 km and a far-field time function 4 sec in duration. The body-wave moment was computed to be 5.0 × 1025 dyne-cm. The surface-wave radiation pattern was found to be consistent with that of the body waves with a surface-wave moment of 6.5 × 1025 dyne-cm. The agreement of the two different moments indicates that the earthquake had a simple source about 4 sec long. A comparison of this earthquake source with the Borrego Mountain and Truckee events demonstrates that all three of these earthquakes behaved as high stress-drop events. El Golfo was shown to be different from the low stress-drop, plate-boundary events which were located on the Gibbs fracture zone in 1967 and 1974.
Glorified optics and wave propagation in nonplanar structure
Authors: Hong Tai-Lin , Helmberger Donald V. 
Published: September 2021

abstract
Waves propagating in varying nonplanar structure can produce many interesting phenomena, such as focusing, caustics, and triplications. A high-frequency technique based on the first-motion approximation, referred to as glorified optics, has been developed to generate synthetic seismograms for these types of problems. The technique, in its simplest form, uses the spreading rate of a beam with transmission and reflection coefficients along each possible ray path. The time behavior of each arrival is either that of the original pulse or its Hilbert transform depending on the position of caustics. The geophysically interesting structure of a soft basin over a half-space is investigated in detail by this method. Synthetic seismograms appropriate for various locations are compared with the results of finite difference and finite element methods. The technique appears rich in insight and should prove very useful in modeling problems.
Investigation of surface-wave dispersion in an inhomogeneous medium by the finite difference method
Authors: Acharya H. K. , Bentley C. R. 
Published: September 2021

abstract
Surface-wave dispersion for the ice sheet of Marie Byrd Land, Antarctica, in which velocity and density increase continuously with depth and gradients near the surface are steep, has been computed by solving the equations of motion directly by finite differences. No simplifying assumptions or approximations about parameter variations with depth have been made. Computer results agree well with observed data without the introduction of any anisotropy, as was needed in a previous analysis (Acharya, 1972). Tests of the assumptions made in the previous analysis show that (a) the approximation Poisson's ratio = 14 introduces no significant error even though Poisson's ratio actually varies from 14 to 13 in the upper part of the ice sheet, and (b) the assumption of a constant density, required if one is to separate compressional and shear-wave displacement potentials, is unsatisfactory.
Investigation of crustal structure by the analysis of reverberation periodicities
Authors: Gir Roopa , Subhash Shiv Mohan G. , Choudhury Mansur A. 
Published: September 2021

abstract
The analysis of reverberation periodicities is shown to be a promising method to study local crustal structure. It is demonstrated with the help of numerical models, that for an average crust; a data length of only 8 to 12 sec is sufficient to derive a crustal model in contrast to about 40 sec or more needed in the Phinney's spectral ratio matching technique.
Examples from numerical models of one- and two-layer crusts are presented. Analysis of five intermediate and deep focus earthquakes, recorded on magnetic tape at the Echery (ECH) observatory of the Institut de Physique du Globe of Strasbourg, shows that while the spectral ratios indicate little overall coherence, the periodicity corresponding to the total crustal thickness is evident in all cases. The possibility of deriving a detailed crustal model is also discussed with the help of results from one of the above events.
Automatic earthquake recognition and timing from single traces
Authors: Allen Rex V. 
Published: September 2021

abstract
A computer program has been developed for the automatic detection and timing of earthquakes on a single seismic trace. The program operates on line and is sufficiently simple that it is expected to work in inexpensive low-power microprocessors in field applications. In tests with analog tapes of earthquakes, the program correctly identified and timed to within 0.05 sec about 70 per cent of the events which would normally be timed in operation of a network. The program evaluates the accuracy of its picks, and its estimates appear to be quite reliable. The algorithm is working at present in a 16-bit minicomputer and appears to be compatible with presently available microprocessors.
Intelligent Indexing and Sorting Management System – Automated Search Indexing and Sorting of Various Topics
Authors: Ganapathy Apoorva , Fadziso Takudzwa 
Published: September 2021

An issue that the majority of the databases face is the static and manual character of indexing activities. This traditional method of indexing and sorting different topics is confirmed to shake the dataset performance somewhat, making downtime and a potential effect in the presentation that is normally addressed by manually indexing operations. Numerous data mining methods can accelerate this process by using proper indexing structures. Choosing the appropriate index generally relies upon the kind of operation that the algorithm performs against the dataset. Topic indexing is the operation of recognizing the principal topics covered by a document. These are helpful for some reasons: as subject headings in libraries, as keywords in scholarly articles, and as hashtags on social media platforms. Knowing a document’s topic assists individuals with deciding its importance quickly. In any case, assigning topics manually is a tedious and redundant task. This paper shows the best way to create them automatically in a way that contends with manual indexing done by humans. This paper also talks about the issues and the techniques for identifying applicable data in a huge variety of documents. The contribution of this thesis to this issue is to foster better content analysis techniques that can be utilized to describe document content with automated index terms. Index terms can be used as meta-data that defines documents and is utilized for seeking various topics. The main point of this paper is to show the way toward creating an automatic indexer which analyzes the topic of documents by integrating proof from word frequencies and proof from the linguistic analysis given by a syntactic parser. The indexer weighs the expressions of a document as per their assessed significance for depicting the topic of a given document based on the content analysis.
Heart rate variability and heart rate turbulence in patients with vasovagal syncope
Authors: Akıncı Sinan , Çoner Ali , Balcıoğlu Akif Serhat , Akbay Ertan , Müderrisoğlu İbrahim Haldun 
Published: September 2021

Aim The autonomic nervous system plays an important role in the pathogenesis of vasovagal syncope, but studies on the effect of basal autonomic tone have found confusing results. The aim of this study was to investigate the effect of basal autonomic functions, as assessed by heart rate variability (HRV) and heart rate turbulence (HRT), in patients with vasovagal syncope.Material and methods Patients who underwent head-up tilt test (HUTT) due to unexplained syncope and who had a 24 hr Holter ECG recording in the same period were retrospectively analyzed. Patients with diabetes, a history of myocardial infarction, heart failure, orthostatic hypotension, atrial fibrillation, or use of vasoactive drugs, such as beta blockers, were excluded from the study. 161 patients who met these criteria were included in the study. Time domain HRV parameters from Holter ECG recordings and HRT parameters from patients with sufficient number of ventricular premature contractions were measured.Results The age of the patients varied from 16 to 75 yrs (mean: 44.8±18.5 yrs). HUTT results of 60 (37.2 %) patients were evaluated as positive. There were no significant differences in the basal demographic, clinical, or laboratory findings of the tilt-positive and tilt-negative patient groups. Likewise, there were no significant differences between the time domain HRV parameters and HRT parameters of both groups.Conclusion HRV and HRT parameters reflecting basal autonomic function were not different between HUTT positive and HUTT negative patient groups. These findings suggest that basal autonomic functions have no effect on vasovagal syncope pathogenesis.