bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of distance on local magnitudes found from strong-motion records
Authors: Jennings Paul C. , Kanamori Hiroo 
Published: July 2021

abstract
Values of local magnitude ML, are calculated from 56 strong-motion accelerograms recorded in the Imperial Valley earthquake of 15 October 1979 according to procedures developed earlier (Kanamori and Jennings, 1978). These data, plus similar data from the San Fernando earthquake of 9 February 1971 and additional, less numerous data from several other California earthquakes, are used to investigate the use of different measures of distance in near-field determinations of ML: this investigation has relevance for similar uses of distances in determining seismic design criteria. In addition, the consistency of the values of ML found from the strong-motion data is examined from the viewpoint of assessing the need for any correction in the standard attenuation curve, −log10A0(Δ).
It was found that the most consistent values of ML result when distance is measured to the closest point on the surface trace of the fault if a site lies within a circle with diameter equal to the extent of faulting and centered on the center of faulting (center of energy release). Outside this circle, the distance measured to the center of the circle is recommended.
A consistent trend in the values of ML found from strong-motion records is seen in the data. The values start, at zero distance, at essentially the far-field value and then decrease to −1/4 unit at about 20 km. Then they rise to +1/4 unit at 50 to 60 km. A smooth revision to the standard attenuation curve is presented which removes this systematic trend.
Building damage at Charleston, South Carolina, associated with the 1886 earthquake
Authors: Robinson Andrew , Talwani Pradeep 
Published: July 2021

abstractFollowing the Modified Mercalli Intensity X 31 August 1886 earthquake, a privately published report described the damage sustained by each of the approximately 7,000 buildings in Charleston, South Carolina. We have examined this report to seek the factors that contributed to the observed damage. An analysis of the data suggests that the type of material used in the construction was the most important single factor and the site location (made versus solid ground) a secondary one. Over 80 per cent of the damaged buildings were of brick construction. Only a slightly higher proportion of brick buildings located on made ground (69 per cent) suffered compared to those located on firm ground (63 per cent). Only 7 per cent of wood frame structures sustained damage, of these 96 per cent were located on made ground.
Numerical evaluation of near-field, high-frequency radiation from quasi-dynamic circular faults
Authors: Campillo Michel 
Published: July 2021

abstractWe compute the near-field, high-frequency radiation from a circular crack expanding with constant rupture velocity and discuss the characteristics of the stopping phases. We then introduce rupture velocity jumps in the fracture process. The computed accelerations show the dominant role played by the rupture front kinematics. The high acceleration pulses are associated with sudden changes of the rupture velocity. For a sudden jump (or a sudden stop), there is no theoretical high-frequency limit to the spectral density of acceleration. In order to account for fmax, we introduce a smooth deceleration of the rupture front over a time t′ in place of a sudden stop. This results in a spectral fall-off for frequencies greater than 1/t′ and supports the interpretation of fmax as a source effect.
Maximum likelihood estimation of b values for magnitude grouped data
Authors: Bender Bernice 
Published: July 2021

abstract
The b value estimated by fitting a set of observed earthquake magnitudes to the magnitude-frequency relationship, log N(m) = a - bm, where N(m) = number of earthquakes exceeding magnitude m, is correlated with the fitting technique used. Both so-called interval and cumulative least-squares fits to the formula log N(m) = a - bm tend statistically to estimate too low a b value, because they cannot include magnitudes above the maximum observed. Maximum likelihood formulas (Aki, Utsu, and Page) for exact or continuous magnitudes give biased results if they are applied to interval data, with the bias increasing as interval size increases. The bias is small at magnitude intervals Δm = 0.1, but significant if the formulas are applied to magnitudes which have been recovered from historic intensity data at intervals of 0.6 magnitude unit. Corrections for interval size can be applied to the continuous data formulas to make them equivalent to the formula derived specifically for grouped data (e.g., Karnik, 1971). A simpler form of the grouped data formula is derived here and shows the role of interval size and maximum magnitude on the b value obtained. This paper also shows how, given a population value of b, to calculate the distribution of the estimated b values. Conversely, this paper derives an a posteriori distribution for the population b value, given the magnitudes of an observed set of earthquakes.
The distribution of b values fitted by various techniques is illustrated for a number of cases. Several illustrations of probabilistic ground motions calculated for a range of b values show that a small fractional change in the assumed b value can have a substantially larger fractional effect on the ground motion calculated.
A specific barrier model for the quantitative description of inhomogeneous faulting and the prediction of strong ground motion. Part II. Applications of the model
Authors: Papageorgiou Apostolos S. , Aki Keiiti 
Published: July 2021

abstractThe specific barrier model, which was described in detail by Papageorgiou and Aki (1983), is applied to a set of five moderate to strong Californian earthquakes: Kern County (1952); San Fernando (1971); Borrego Mountain (1968); Long Beach (1933); and Parkfield (1966). Source parameters such as barrier intervals, local stress drops, cohesive zone size, and cohesive stress are inferred. The analysis of the San Fernando earthquake of 1971 revealed a strong frequency dependence of Qβ, suggesting that the high frequencies may not be as strongly attenuated as initially thought. This suggests that the fall-off at high frequencies of observed spectra at a site may not be a propagation path effect but primarily a source effect. The cut-off frequency observed on the source acceleration power spectra of all the events analyzed in this paper, is interpreted in terms of the cohesive zone size and cohesive stress which arrest the localized fractures that occur on the fault plane. It was found that the barrier interval, as inferred by the specific barrier model, increases with the increase in maximum slip. The ratio of the latter to the former represents the local strain drop and was found to increase slightly (factor of 2) with earthquake size. This verifies the relation between barrier interval and maximum slip which has been observed by Aki et al. (1977) who inferred the barrier interval by different methods (i.e., surface measurement of fault slip, seismic measurement of rise time, scaling law of seismic spectrum). Striking similarities with respect to source parameters were found between the Fort Tejon (1857) and Kern County (1952) earthquakes as well as between the Long Beach (1933) and Parkfield (1966) earthquakes. The former are characterized by long barrier intervals and large slips while the latter are characterized by short barrier intervals and small slips. San Fernando (1971) and Borrego Mountain (1968) earthquakes lie in between these two extremes.
Possibility of induced seismicity in the vicinity of the Sleepy Hollow oil Field, southwestern Nebraska
Authors: Rothe George H. , Lui Chung-Yao 
Published: July 2021

Abstract
An array of four seismographs operating in northwestern Kansas and southwestern Nebraska detected 31 earthquakes in the magnitude range 0.6 to 2.9 from March 1979 to March 1980. Of these, 22 were recorded at enough stations to allow accurate location, and at least three of them were felt by local residents. Sixteen of the located events occurred in the immediate vicinity of the most productive oil field in Nebraska: the Sleepy Hollow Field. A mail canvass revealed a well-constrained “felt” area about 10 km across which coincides remarkably well with the oil field. Water injection has been used as a method of enhanced recovery in this field since 1966. Some of the earthquakes occurred on possible downward extensions of faults in the deeper sedimentary rocks and granite basement, implying that some of the seismicity may be induced. Deeper events and other supporting data, however, suggest current tectonic activity on the Chadron-Cambridge Arch. The recently installed eight-station Sleepy Hollow Seismic Network should provide the data necessary to test these hypotheses.
Interpretation of seismic reflection profiling data for the structure of the San Andreas fault zone
Authors: Feng R. , McEvilly T. V. 
Published: July 2021

AbstractA seismic reflection profile crossing the San Andreas fault zone in central California was conducted in 1978. Results are complicated by the extreme lateral heterogeneity and low velocities in the fault zone. Other evidence for severe lateral velocity change across the fault zone lies in hypocenter bias and nodal plane distortion for earthquakes on the fault. Conventional interpretation and processing methods for reflection data are hard-pressed in this situation. Using the inverse ray method of May and Covey (1981), with an initial model derived from a variety of data and the impedance contrasts inferred from the preserved amplitude stacked section, an iterative inversion process yields a velocity model which, while clearly nonunique, is consistent with the various lines of evidence on the fault zone structure.
Source dimensions and stress drops of small earthquakes near Parkfield, California
Authors: O'Neill M. E. 
Published: July 2021

AbstractSource dimensions and stress drops of 30 small Parkfield, California, earthquakes with coda duration magnitudes between 1.2 and 3.9 have been estimated from measurements on short-period velocity-transducer seismograms. Times from the initial onset to the first zero crossing, corrected for attenuation and instrument response, have been interpreted in terms of a circular source model in which rupture expands radially outward from a point until it stops abruptly at radius a. For each earthquake, duration magnitude MD gave an estimate of seismic moment MO and MO and a together gave an estimate of static stress drop.All 30 earthquakes are located on a 6-km-long segment of the San Andreas fault at a depth range of about 8 to 13 km. Source radius systemically increases with magnitude from about 70 m for events near MD 1.4 to about 600 m for an event of MD 3.9. Static stress drop ranges from about 2 to 30 bars and is not strongly correlated with magnitude. Static stress drop does appear to be spatially dependent; the earthquakes with stress drops greater than 20 bars are concentrated in a small region close to the hypocenter of the magnitude 512 1966 Parkfield earthquake.
Dependence of sediment-filled valley response on input amplitude and valley properties
Authors: Tucker B. E. , King J. L. 
Published: July 2021

AbstractFor three sediment-filled valleys, average site responses were experimentally determined and found to apply, to within ±0.25 log units, to earthquakes at any azimuth and to S waves and coda waves; for one of these valleys, ground accelerations were measured over the range 10−5 to 0.2 g, and no significant differences in site responses were apparent. In two valleys with sediment-basement impedance contrasts of 5:1 and 6:1, average site amplification is as much as a factor of five in certain frequency bands. In another valley, with a sediment-basement impedance contrast of 3:1, sediment amplification is about a factor of two. The duration of motion on the valley sediments, in narrow frequency bands, is equal to that on the bordering rock, implying that the observed amplification is not due to a high-Q resonance of the sediments.
Foreshock and aftershock activity of the 1976 Mesa de Andrade, Mexico, earthquake
Authors: Gonzalez J. Javier , Nava F. Alejandro , Reyes C. Alfonso 
Published: July 2021

AbstractStudy of the aftershocks of the 7 December 1976, Mesa de Andrade, earthquake (ML = 5.3, MS = 5.7) on the Cerro Prieto fault in the Colorado River Delta, indicates a simple strike-slip transform fault mechanism. The fault plane defined by aftershocks is essentially vertical with a surface projection 1.5 km southwest of the surface trace of the Cerro Prieto fault. The main shock was complex and consisted of two large events. Aftershock hypocenters are distributed in two clusters separated by a gap suggestive of an unbroken barrier.Station corrections of about 0.7 sec are indicated for arrival-time locations using stations both on the deltaic sediments and on the surrounding basement outcroppings (assuming a flat-layered velocity model). Differences of some 10 to 15 km are found between epicenters obtained using only United States stations and epicenters obtained with the addition of Mexican local stations.Foreshock activity, recorded on a portable seismic network, was located in a zone coincident with the northern aftershock cluster. The abrupt onset of foreshock activity emphasizes the importance of continuous monitoring of the Colorado River Delta area in any scheme of earthquake risk studies.
A catalog of shallow earthquakes of Mexico from 1900 to 1981
Authors: Singh S. K. , Rodríguez M. , Espindola J. M. 
Published: July 2021

AbstractA catalog of shallow earthquakes (depth ≦ 65 km) of Mexico (15° to 20°N, 94.5° to 105.5°W) covering the period 1900 to 1981 is presented. The catalog includes only those events whose magnitudes (M, Ms, or magnitude from Pasadena) are ≧5.9. It is most likely complete for shocks with Ms ≧6.5 from July 1906 to December 1981. For many shocks, Ms has been determined from Uppsala bulletins and/or Uppsala and Göttingen Wiechert Seismograms. The statistics of incremental frequency n(Ms) shows a peak at Ms ≃ 7.7, reinforcing a previous observation by Singh et al. (1981). In the range 6.4 ≦ Ms ≦ 7.5, the observed n(Ms) deviates significantly from an exponential distribution. The catalog provides a basis for further statistical analysis of earthquakes in Mexico.
Late quaternary history of the Stillwater seismic gap, Nevada
Authors: Wallace Robert E. , Whitney Robert A. 
Published: July 2021

AbstractFault scarps that formed during the 1915 and 1954 earthquakes in central Nevada are roughly aligned, but are separated by a gap of 40 km. The gap contains no historical scarps and has been termed the Stillwater seismic gap. The abundance, size, and distribution of prehistorical fault scarps is similar in the Stillwater seismic gap and the 1915 and 1954 earthquake areas, and overall height and long-term uplift rates of range blocks are similar throughout the area studied; thus, the faults in the gap do not appear to be locked or appreciably more or less active on a long-term basis than those in areas of the 1915 and 1954 earthquakes. None of the scarps in the gap is likely younger than about 300 yr, so that no major earthquake occurred in that period.The Stillwater seismic gap is part of the central Nevada-eastern California seismic belt, where large-scale surface faulting events have occurred at intervals of a few years to a few decades in a pattern that suggests incremental filling of the belt. If that pattern of belt-filling continues, the Stillwater gap is a likely site for future major faulting, but the low level of seismicity in the gap area suggests that the next major earthquake there is not imminent.
A new asymptotic method for the modeling of near-field accelerograms
Authors: Bernard P. , Madariaga R. 
Published: July 2021

AbstractWe study high-frequency radiation from a dislocation model of rupture propagation at the earthquake source. We demonstrate that in this case all the radiation emanates from the rupture front and, by a change of variables, that at any instant of time the high-frequency waves reaching an observer come from a line on the fault plane that we call isochrone. An asymptotic approximation to near-source velocity and acceleration is obtained that involves a simple integration along the isochrones for every time step. It is shown that wave front discontinuities (critical or stopping phases) are radiated every time an isochrone becomes tangent to a barrier. This leads to what we call the critical ray approximation which is given in a closed form. The previous results are compared with discrete wavenumber synthetics obtained by Bouchon (1982) for the Gilroy 6 recording of the Coyote Lake earthquake of 1980. The fit between the asymptotic and full numerical method is extremely good. The critical ray approximation permits the identification of different phases in Bouchon's synthetics and the prediction of the behavior of the signal in the vicinity of their arrival time.
Stress analysis of rectangular walls under seismically induced hydrodynamic loads
Authors: Haroun Medhat. A. 
Published: July 2021

AbstractSeismically induced bending moments in the walls of rectangular concrete liquid storage tanks are evaluated. The tank is assumed to be subjected to simultaneous horizontal and vertical components of earthquake excitations. The liquid is assumed to be homogeneous, inviscid, and incompressible. Hydrodynamic pressures are calculated using the classical potential flow approach and are compared with those obtained from approximate analyses. Typical systems of loadings are identified and applied on the walls which are assumed to behave as elastic plates. Analytical expressions for the computation of internal moments are presented, and numerical values of moment coefficients are tabulated for use in seismic design analysis of tank walls.
Source parameters for aftershocks of the Oroville, California, earthquake
Authors: Fletcher Jon , Boatwright John , Haar Linda , Hanks Thomas , McGarr Art 
Published: July 2021

AbstractA suite of 111 strong-motion accelerograms for 14 aftershocks of the Oroville, California, earthquake (ML = 5.7, 1 August 1975) that range in local magnitude (ML) from 2.8 to 5.2 has been analyzed to obtain estimates of seismic moment (Mo), source radius (ro), and stress drop (Δσ) in addition to the focal parameters of location, depth, and fault-plane solution. This data set, which is unusually complete for near-source (Δ ≲ 20 km) on-scale readings, allows for greater precision in the calculation of various measures of stress difference as represented by the Brune stress drop, the apparent stress, the arms stress drop, and the dynamic stress drop. In addition, the seismicity following each aftershock and state-of-stress seem to correlate with particular estimates of stress drop.Seismic moments were calculated from the asymptotic long-period spectral levels which were corrected for the radiation pattern of a double-couple point source. They range from 1.4 × 1021 dyne-cm for a ML = 2.8 shock to 3.3 × 1023 dyne-cm for a ML = 5.1 event. A least-squares fit between ML and the logarithm Mo yieldslog M 0 = ( 1.36 ± 0.22 ) M L + ( 16.8 ± 1.1 ) for M L ≧ 4.3andlog ⁡ M 0 = ( 1.1 ± 0.14 ) M L + ( 18 ± 0.51 ) for M L ≦ 4.1.These relationships are qualitatively in agreement with the response of the Wood-Anderson instrument to a Brune pulse. Stress drops from the Brune formulation range about 14 to 170 bars. Stress drop is correlated with depth in that the deepest events have the largest stress drops and no large stress drops occur at the shallow depths. Apparent stresses are smaller than the Brune stress drops and show a weaker depth dependence over the depth interval for which they are available. The stress drop calculated from the rms of acceleration (arms) was approximately constant at about 90 bars for 5 of the 7 larger events analyzed; the two high values of 160 and 190 bars were obtained only for the two events which had marked aftershock sequences of their own. These results may be interpreted in terms of the state-of-stress, simple fracture criteria, and mechanisms for the generation of aftershocks. The increase with depth of the envelope of the Brune stress drops may be caused by an increase in shear stress from overburden pressure. Smaller stress drop events can occur at any depth interval. The causal mechanism of aftershocks is not known, but probably includes a change in the frictional properties of the fault, suggesting that the arms stress drop is a measure of the frictional or dynamic stress release.
Estimates of short-periodQvalues and seismic moments from coda waves for earthquakes of the Beijing and Yun-nan regions of China
Authors: Chen Peishan , Nuttli Otto W. , Ye Wenhua , Qin Jiazheng 
Published: July 2021

AbstractCoda waves are used to determine the Q value of short-period waves in the Beijing area and in Yun-nan Province, China, and the seismic moments of the earthquakes studied. For the Beijing area the Q0, or 1-Hz value, is found to be approximately 400, with little or no indication of frequency dependence of Q for frequencies near 1 Hz in that region. For Yun-nan Province, the Q0 value is about 180, and the data suggest that Q(f) = Q0f0.2, where f is wave frequency. These values are in fairly good agreement with short-period Q estimates made for those regions by Chen and Nuttli (1984), on the basis of attenuation of seismic intensity values.Hermann's (1980) application of Aki's (1969) coda wave theory is extended, to provide simple equations for calculating master curves for coda wave studies. Two types of master curves provide independent estimates of Q0 and of the dependency of Q on wave frequency. For the data analyzed the two methods gave similar results. A third type of master curves gives estimates of the seismic moments of the earthquakes studied. The moments obtained by this means agree with values obtained by the conventional methods of analysis that use the spectrum of body waves or surface waves.
Statistical aspects of New England seismicity from 1975 to 1982 and implications for past and future earthquake activity
Authors: Ebel John E. 
Published: July 2021

AbstractThe seismicity of New England from 1 October 1975 to 30 November 1982 has been studied to determine how well it represents past seismicity and what it might imply about future earthquakes. Just over 100 earthquakes with magnitudes between 2.0 and 4.7 were recorded during this modern time period, while the historic earthquake catalog of Chiburis (1981) lists 760 earthquakes in New England from 1568 to 1975, the largest having maximum Modified Mercalli intensity VII shaking. The spatial distribution of the recent seismicity reproduces that for the historical seismicity patterns quite well, with the larger earthquakes in the modern record having preferentially occurred along coastal and lowland New England or in central New Hampshire. Space-time plots show that the seismicity displays considerable spatial variation, and that there are only vague hints of migrations of epicenters. The number of earthquakes as well as the amount of seismic energy release appear essentially random in time, and the recurrence curve for the modern time period (log number of events versus magnitude) is a straight line for events between magnitudes 2 and 4.5 with a b value of 0.84 (±0.03). The sizes of the largest earthquakes in the historic record are those which would be expected by extrapolating the present seismicity rate backward in time using a Gumbel type I distribution. One major discrepancy between the statistics of the recent and historic catalogs is that the latter does not have as many moderate (magnitudes 5 to 5.8) earthquakes as would be expected from the recent data. This discrepancy could be due to inaccuracies in the historic catalog, to unusually high recent seismicity or to a real historical shortage of such moderate magnitude earthquakes. Large earthquakes may be more likely to happen in areas of past and present high seismicity, especially in central and southern New Hampshire, along coastal Maine, and along the south coast to New England.