bluuebunny/crossref_metadata_2025_split huggingface dataset:
Co-seismic displacements of the 1992 landers earthquake sequence
Authors: Hudnut K. W. , Bock Y. , Cline M. , Fang P. , Feng Y. , Freymueller J. , Ge X. , Gross W. K. , Jackson D. , Kim M. , King N. E. , Langbein J. , Larsen S. C. , Lisowski M. , Shen Z.-K. , Svarc J. , Zhang J. 
Published: September 2021

Abstract
We present co-seismic displacement vectors derived from Global Positioning System (GPS) measurements of 92 stations in southern California. These GPS results are combined with five well-determined GPS displacement vectors from continuously tracking stations of the Permanent GPS Geodetic Array, as well as line-length changes from USGS Geodolite and two-color laser trilateration observations, to determine a self-consistent set of geodetic data for the earthquake. These combined displacements are modeled by an elastic dislocation representation of the primary fault rupture planes. On average, the model residuals are about twice the estimated measurement errors.
Seismic radiation from circular cracks growing at variable rupture velocity
Authors: Sato Tamao 
Published: September 2021

AbstractWe have investigated the far-field body waves emitted by a circular fault growing at variable rupture velocity. The slip motion on the fault is constructed by assuming that the self-similar slip distribution holds at every successive instant of rupture formation for a circular crack. The present method permits us to evaluate not only the high-frequency but also the low-frequency radiation. It is also possible to handle both abrupt and continuous change in rupture velocity. The resultant expression for the radiation does not involve an integral. It is expressed in a closed form that contains information about the isochrone properties of the two extreme points having the minimum and maximum distances from the observer. Because of its simplicity and high computational speed, the present method provides us with a basic tool for simulating the radiation from seismic sources with a multitude of irregular rupture growth. The property of acceleration pulse radiated by continuous change in rupture velocity has been investigated. The time duration of the velocity change is assumed to be short but to take a finite time. The shape of the rupture front that is effective in radiating the high-frequency radiation is presumed to be semicircular. The acceleration pulse demonstrates a directivity with respect to both the pulse width and amplitude. The pulse width is, on average, given by the duration of the velocity change, and it is modulated by the directivity factor, which depends on the rupture velocity averaged over the change in rupture velocity. The pulse width radiated toward the growth direction of the semi-circular rupture front is shorter than that radiated toward the opposite side. The spectral amplitude of the acceleration pulse depends linearly on the strain, the radius of the rupture front at which the rupture velocity starts to change, the magnitude of the change in rupture velocity, and the generalized radiation pattern coefficient. The directivity of the radiation pattern coefficient is stronger than that for the case of an abrupt change in rupture velocity. In the case where the rupture stops completely, the radiation pattern coefficient is simply controlled by the magnitude of the change in rupture velocity. If we deal with a partial drop of the rupture velocity, however, we must consider the average rupture velocity as well to fully describe the radiation pattern. A procedure is presented for retrieving the model parameters from acceleration pulse data. The present results with regard to the acceleration pulse do not require the coherent movement of the rupture front over the entire circle. The results are applicable to more general cases where the rupture front moves coherently over a certain restricted segment, though the range of the segment has to become wider as the duration of the change in rupture velocity increases.
Characteristics of long-period microtremors and their applicability in exploration of deep sedimentary layers
Authors: Yamanaka Hiroaki , Takemura Masayuki , Ishida Hiroshi , Niwa Masanori 
Published: September 2021

AbstractApplicability of long-period microtremors in inferring subsurface structure is examined using measurements of microtremors in the northwestern part of the Kanto Plain in Japan. Short-term continuous measurements of long-period microtremors at both sediment and basement sites were taken. A spectral peak at a period of 4 to 5 sec is stable with time, while peaks at periods less than 2 sec are time variant, suggesting a variation of microtremor sources. However, it was found that the spectral ratio between vertical and horizontal microtremors (ellipticity) at each site is stable with time. Good agreement was found between ellipticities of microtremors at the sediment site and those computed for Rayleigh waves in which the structure of the sediments beneath the site was taken into account. We also found that the ellipticities of Rayleigh waves in earthquake ground motions were consistent with those of the microtremors. These comparisons provide strong evidence that long-period microtremors in the area studied consist mainly of Rayleigh waves. The ellipticity of microtremors was investigated by observing microtremors at temporary observation sites in the Kanto Plain where the sediment thickness varied from 0 to 1 km. The subsurface structures were deduced by trial-and-error fitting of observed ellipticities with theoretical ellipticities that were calculated assuming Rayleigh waves. These results show that ellipticity of long-period microtremors is effective for deducing structure from microtremor data at a single site.
Errors in hypocenter location: Picking, model, and magnitude dependence
Authors: Billings S. D. , Sambridge M. S. , Kennett B. L. N. 
Published: September 2021

AbstractThe location procedures of seismic events are influenced by two major classes of errors, the error in picking individual seismic phases and modeling error due to the departure of the real Earth from the reference model used in the location. Both classes of error influence the estimate of location and it is difficult to separate them.The role of picking errors can be assessed by a nonlinear analysis using a Monte Carlo procedure. Arrivals times are perturbed with random numbers drawn from a normal distribution, and the event is relocated using these perturbed arrival times. By repeating the procedure many times, a cluster of locations is obtained, which can be used to investigate the effects of picking errors on the hypocenter. This analysis is insensitive to velocity-model errors as these are fixed for a given combination of stations and phases. Some care must be exercised when analysing multidimensional distributions in two-dimensional slices because of a projection effect.The modeling error due to the influence of lateral heterogeneity in the Earth is examined by comparing the locations of the same event using different combinations of phases and network geometries, which reinforces the need to use arrivals other than P for accurate depth resolution. The sensitivity of P arrivals to changes in depth are swamped by model errors, and inclusion of depth-sensitive phases such as pP is highly recommended. The effect of picking errors on location is found to be much smaller than the mislocation caused by neglecting lateral heterogeneity when only P arrivals are used. Consequently, the Monte Carlo analysis, which is primarily aimed at picking errors only, is most appropriate when multiple phases have been used to more accurately constrain the hypocenter, especially for the depth component.Altering the type of phase data used in the location plays a similar role in changing the network geometry, in that both are mechanisms that influence the nature of the constraint on the hypocenter. By relocating events with network geometries corresponding to the different magnitudes, it is found that the location of the event can be affected significantly by the magnitude, and when using robust statistics to describe earthquake residuals, the mislocation can occur in a systematic manner. The effect is marked in regions with significant lateral variations in seismic velocities. For example, low-magnitude events in the Flores Sea are found to be dragged toward Australia as a result of the fast paths to Australian stations relative to the iasp91 reference velocity model.
On the correlation of observed Gutenberg-Richter'sbvalue and Omori'spvalue for aftershocks
Authors: Wang Jeen-Hwa 
Published: September 2021

AbstractThe correlation of Gutenberg-Richter's b value and Omori's p value is studied based on the data of p versus b values for several tens of worldwide earthquakes. Although the distribution of data points is dispersive, a negative correlation between the two parameters can still be recognized. The slope value of the regression line is about -0.58.
Ground-motion relations for eastern North America
Authors: Atkinson Gail M. , Boore David M. 
Published: September 2021

AbstractPredictive relations are developed for ground motions from eastern North American earthquakes of 4.0 ≦ M ≦ 7.25 at distances of 10 ≦ R ≦ 500 km. The predicted parameters are response spectra at frequencies of 0.5 to 20 Hz, and peak ground acceleration and velocity. The predictions are derived from an empirically based stochastic ground-motion model. The relations differ from previous work in the improved empirical definition of input parameters and empirical validation of results. The relations are in demonstrable agreement with ground motions from earthquakes of M 4 to 5. There are insufficient data to adequately judge the relations at larger magnitudes, although they are consistent with data from the Saguenay (M 5.8) and Nahanni (M 6.8) earthquakes. The underlying model parameters are constrained by empirical data for events as large as M 6.8.
A method for direct computation of the differential seismogram with respect to the velocity change in a layered elastic solid
Authors: Zeng Yuehua , Anderson John G. 
Published: September 2021

Abstract
We derived a method to compute the differential seismogram directly in a layered elastic half-space. This method first computes a differential field caused by the velocity change in the layer and then multiplies it with the original elastic wave field. This product acts like a source, and the seismogram caused by this source term is the differential seismogram. The differential waves are propagated directly to the receiver in frequency/wavenumber domain using the generalized reflection and transmission coefficient method. In comparison with the typical finite-difference approach to compute a complete set of differential seismograms at one station in an N-layered earth model, our method not only saves about N/2 folds of computation time but also leads to a more accurate solution. Thus, it provides an efficient and direct procedure to compute the differential seismogram for a complete waveform fitting in a layered elastic earth model.
Experimental study of site effects in the Fort-de-France area (Martinique island)
Authors: Gagnepain-Beyneix J. , Lépine J. C. , Nercessian A. , Hirn A. 
Published: September 2021

AbstractWe used weak-motion recordings of regional events to quantify the site effects in the Fort-de-France (Martinique) area in the frequency band 1 to 25 Hz. The studied area extends over three distinct geological units: the Morne-Pitault volcanic massif (15 to 11 M.A.), the Carbet volcanic massif (4 to 2 M.A.), and the Lamentin alluvial plain (quaternary age). The topography being complex, 31 sites were selected in order to get a representative sampling of the various topographical and geological configurations. The large number of studied sites also allowed us to define a reference site whose selection was not obvious. Large broadband amplifications are observed in the Lamentin plain instead of the expected peak resonances. More surprising, such resonance is observed around 2 to 3 Hz on several sites of the volcanic Vauclain-Pitault chain, though no sedimentary layer is present. On the other hand, in the inner Fort-de-France where significant effects were expected because of the very complex topography, no large amplication is observed except for at one site. Clear three-dimensional (3D) effects are also observed at some stations. Though not very well documented, the low-frequency behavior deduced from teleseismic observations seems rather different, illustrating the difficulty in finding a convenient reference site in such a volcanic area.
Modeling of source rupture characteristics for the Saguenay earthquake of November 1988
Authors: Haddon R. A. W. 
Published: September 2021

AbstractThe magnitude mb = 6.0 Saguenay earthquake of 25 November 1988 in Quebec, Canada, was one of the largest to have occurred in eastern North America during the past half-century. Recorded high-frequency ground motions exceeded anticipated values for an event of its size by a factor of 10 on both the regional network and strong-motion instruments. Two proposed explanations for the discrepancy are (1) that the source was a rare “high stress drop” event and (2) that it was an asymmetrical “fractional stress drop” rupture (involving only normal effective stresses). In this article, detailed fault-slip models are derived to fit characteristics of strong-motion displacement, velocity, and acceleration data. The results establish that the effective rupture stress was normal (less than 100 bars), that the fault rupture was highly asymmetrical with respect to the point of rupture initiation, and that the average slip time for points within the rupture area (approx. 0.2 sec) was considerably less than that associated with the standard Brune (1970) source spectral model. The rupture area developed in a number of episodes, each widening or lengthening the previously ruptured area, which may explain the short average slip time. The results indicate that the widely used assumption in hazard analyses that earthquake spectra are adequately represented by the standard Brune (1970) complete stress drop model may be seriously unreliable for prediction of strong ground motion in eastern North America.
Revised dislocation model of the 1986 Chalfant Valley earthquake, eastern California
Authors: Savage J. C. , Gross W. K. 
Published: September 2021

Abstract
A revised dislocation model is proposed to describe the 1986 Chalfant Valley rupture. Leveling data from surveys across the epicentral area are inconsistent with any appreciable dip-slip component in the oblique-slip model that we had proposed earlier. The revised model involves right-lateral slip on the northwest trending main rupture surface and left-lateral slip on the conjugate foreshock rupture surface.
Inversion of regional surface-wave spectra for source parameters of aftershocks from the 1992 Petrolia earthquake sequence
Authors: Tinker Mark Andrew , Beck Susan L. 
Published: September 2021

AbstractRegional distance surface waves are used to study the source parameters for moderate-size aftershocks of the 25 April 1992 Petrolia earthquake sequence. The Cascadia subduction zone had been relatively seismically inactive until the onset of the mainshock (Ms = 7.1). This underthrusting event establishes that the southern end of the North America-Gorda plate boundary is seismogenic. It was followed by two separate and distinct large aftershocks (Ms = 6.6 for both) occurring at 07:41 and 11:41 on 26 April, as well as thousands of other small aftershocks. Many of the aftershocks following the second large aftershock had magnitudes in the range of 4.0 to 5.5. Using intermediate-period surface-wave spectra, we estimate focal mechanisms and depths for one foreshock and six of the larger aftershocks (Md = 4.0 to 5.5). These seven events can be separated into two groups based on temporal, spatial, and principal stress orientation characteristics. Within two days of the mainshock, four aftershocks (Md = 4 to 5) occurred within 4 hr of each other that were located offshore and along the Mendocino fault. These four aftershocks comprise one group. They are shallow, thrust events with northeast-trending P axes. We interpret these aftershocks to represent internal compression within the North American accretionary prism as a result of Gorda plate subduction. The other three events compose the second group. The shallow, strike-slip mechanism determined for the 8 March foreshock (Md = 5.3) may reflect the right-lateral strike-slip motion associated with the interaction between the northern terminus of the San Andreas fault system and the eastern terminus of the Mendocino fault. The 10 May aftershock (Md = 4.1), located on the coast and north of the Mendocino triple junction, has a thrust fault focal mechanism. This event is shallow and probably occurred within the accretionary wedge on an imbricate thrust. A normal fault focal mechanism is obtained for the 5 June aftershock (Md = 4.8), located offshore and just north of the Mendocino fault. This event exhibits a large component of normal motion, representing internal failure within a rebounding accretionary wedge. These two aftershocks and the foreshock have dissimilar locations in space and time, but they do share a north-northwest oriented P axis.
Nonstationary Poisson model for earthquake occurrences
Authors: Hong L.-L. , Guo S.-W. 
Published: September 2021

AbstractA nonstationary Poisson model describing the occurrences of clustering earthquakes is developed. This model, characterized by a U-shape mean-occurrence-rate function, simulates the decreasing, nearly constant, and increasing variations of the mean occurrence rates at the instants soon after the last event in the current cluster, in the waiting period between the current and the next clusters, and just before the next cluster, respectively. The parameters of such a U-shape function are determined empirically from the earthquake catalog. A simple example is presented to show the difference in the estimated mean occurrence rate and in the induced seismic risk between different Poisson occurrence models.
Signal-coil calibration of electromagnetic seismometers
Authors: Rodgers Peter W. , Martin Aaron J. , Robertson Michelle C. , Hsu Mark M. , Harris David B. 
Published: September 2021

AbstractWe show that electromagnetic (em) seismometers may be easily and accurately calibrated by removing a step of current from their signal coil, and simultaneously switching the signal coil to a recorder to capture the response. A theory is developed that obtains the damped generator constant, resonant frequency, and damping ratio from the output of a system identifier used to analyze the response. Only the seismometer mass (from the manufacturer) and the applied current (measured) need be known for a complete calibration. The coil and damping resistances are not required. The method is confirmed by comparing this signal-coil method with weight-lift and calibration-coil calibrations. For a GS-13 V seismometer, these results were within 1.3% of each other. The undamped generator constant computed from the damped generator constant obtained by the signal-coil method matched the generator constant given by the manufacturer to better than 1%. Calibration of nine new L-4C components resulted in undamped generator constants all within 3% of the values given by the manufacturer. The circuit used in the signal-coil method is shown and explained.
ModelingP-Rgconversions from isolated topographic features near the NORESS array
Authors: Clouser Robert H. , Langston Charles A. 
Published: September 2021

AbstractUsing the T-matrix, or extended boundary condition, method, we model seismic-wave scattering from earth models with one-dimensional (1D) isolated topographic features. The earth model is simple, but we are primarily interested in free surface interactions. Scattering phenomena encountered in this model would presumably also operate in more realistic two-dimensional (2D) models. This study is motivated by observations suggesting that surface topography generates coda waves, which are relatively large-amplitude arrivals following major seismic phases. For sinusoidal periodic surfaces, large-amplitude anomalies in the surface displacement spectrum correspond to P-to-Rayleigh (P-Rg), S-to-Rayleigh (S-Rg), and other mode conversions. For isolated topographic features, these conversions still exist. We modeled teleseismic P-Rg conversions from isolated hills in order to understand and confirm the origin of observed conversions near the NORESS array. Parameter studies indicate that P-Rg and critical P-P conversion amplitudes increase roughly-linearly with scatterer relief, but are insensitive to changes in teleseismic ray parameter. Forward-scattered Rg waves are always two to three times larger than backscattered Rg waves. Poor fits to the observed P-Rg amplitudes (relative to the incident P waves) suggest that more realistic and complicated structure effects must be included. For example, it is well known that P-wave amplitudes vary considerably across the NORSAR array due to subsurface structures.
On the distribution of distances between random points on a sphere
Authors: Lomnitz Cinna 
Published: September 2021

Abstract
The theoretical distribution of distances between random points on the surface of a sphere is derived. The result is a cosine-exponential distribution of distances. This result may be applied in seismology, in order to compare the actual distribution of distances between earthquakes with the expected distribution on the assumption of random occurrence. This provides a criterion for detecting triggering effects at epicentral distances of 2 to 17 fault lengths.
A local-magnitude scale for the western Great Basin-eastern Sierra Nevada from synthetic Wood-Anderson seismograms
Authors: Savage Martha Kane , Anderson John G. 
Published: September 2021

AbstractWe have computed synthetic Wood-Anderson seismograms for over 1100 arrivals at 10 three-component, broadband digital stations in the UNR western Great Basin-eastern Sierra Nevada network. These represent all the available records from local earthquakes over magnitude 3.5 between 1990 and June of 1993, plus selected events of smaller magnitude. There were 77 events ranging in magnitude from 2.2 to 5.9, including four events over magnitude 5. The distances considered ranged from 15 to 600 km, with the best-represented range being from 30 to 450 km. We invert these measurements to determine distance and station corrections appropriate for a local-magnitude scale, constrained by Richter's original definition that an earthquake of ML = 3 will cause a 1-mm zero to peak deflection of the Wood-Anderson seismogram at 100 km from the epicenter. The results between 30 and 450 km were essentially independent of choice of curve-fitting parameters. In the 30- to 500-km distance region, the smooth distance-correction curves were very similar to that determined by Richter (1958), which is still used for southern California earthquakes. We propose to use Richter's distance-correction curve in reporting amplitude magnitudes from our digital network.