Seismic yield estimates from Rayleigh-wave source radiation pattern

1981 ◽  
Vol 71 (4) ◽  
pp. 1269-1286
Author(s):  
Nazieh K. Yacoub
Keyword(s):  
Rayleigh Wave ◽  
Radiation Pattern ◽  
Epicentral Distance ◽  
Source Parameters ◽  
Spectral Amplitude ◽  
Attenuation Coefficients ◽  
Wave Source ◽  
Source Radiation ◽  
Explosive Source ◽  
Double Couple

abstract Rayleigh-wave spectral amplitudes generated by two United States nuclear explosions, Rulison and Rio Blanco, were equalized to epicentral distance of 10°, corrected for geometric spreading and instrument response, and filtered by a narrow-band filter to obtain corrected spectral amplitudes. The corrected spectral amplitudes were used in a least-squares scheme to evaluate the symmetric source radiation pattern parameters and average attenuation coefficients, as functions of frequency. The parameters are: the explosive source; the F factor, which is the ratio of the double-couple source to the explosive source; and the radiation pattern azimuth. The evaluated average attenuation coefficients were used, with the station epicentral distance to adjust the corrected spectral amplitudes to obtain the source spectral amplitude, from which the spectral magnitudes were calculated. The explosive source parameters of the radiation pattern and the spectral magnitudes, at different frequencies, were used to estimate the yields of the above two explosions. The estimated yields for the two explosions are within 2 to 6 per cent of the announced yields. The best yield estimate was obtained from the explosive source parameters which estimated the yields for Rulison at 40.6 kt and Rio Blanco at 88.6 kt. The announced yields for Rulison and Rio Blanco are 40 and 90 kt, respectively.

Attenuation of Rayleigh-wave amplitudes across Eurasia

1977 ◽  
Vol 67 (3) ◽  
pp. 751-769
Author(s):  
Nazieh K. Yacoub ◽  
Brian J. Mitchell
Keyword(s):  
Rayleigh Wave ◽  
Regional Variation ◽  
Wave Amplitude ◽  
Period Range ◽  
Attenuation Coefficients ◽  
Nuclear Explosions ◽  
Amplitude Data ◽  
Standard Deviations ◽  
Data Yield ◽  
Rayleigh Mode

abstract Surface waves generated by six earthquakes and two nuclear explosions are used to study the attenuation coefficients of the fundamental Rayleigh mode across Eurasia. Rayleigh-wave amplitude data yield average attenuation coefficients at periods between 4 and 50 sec. The data exhibit relatively large standard deviations and in some cases the average attenuation coefficients take on negative values which may be due to regional variations of the attenuative properties of the crust, lateral refraction, multipathing and scattering. A method has been developed to investigate the regional variation in the attenuative properties of the Eurasian crust and its effect on surface-wave amplitude data, employing the evaluated average attenuation coefficients for the fundamental Rayleigh mode. For this investigation, Eurasia is divided into two regions, one considered to be relatively stable, and the other considered to be tectonic in nature. This regionalization shows that the tectonic regions exhibit higher attenuation than the stable regions in the period range below about 20 sec, whereas in the period range above about 20 sec, no clear difference can be observed for the two regions. Although the effects of lateral refraction and multipathing may still significantly affect the observations, the regionalization lowers the standard deviations considerably and eliminates the negative values which were obtained in the unregionalized determinations.

Stress Drop Derived from Spectral Analysis Considering the Hypocentral Depth in the Attenuation Model: Application to the Ridgecrest Region, California

2021 ◽  
Author(s):  
Dino Bindi ◽  
Hoby N. T. Razafindrakoto ◽  
Matteo Picozzi ◽  
Adrien Oth
Keyword(s):  
Stress Drop ◽  
Spectral Decomposition ◽  
Epicentral Distance ◽  
Source Parameters ◽  
S Wave ◽  
Qualitative Comparison ◽  
Ground Shaking ◽  
Attenuation Model ◽  
Hypocentral Distance ◽  
The Impact

ABSTRACT We investigate the impact of considering a depth-dependent attenuation model on source parameters assessed through a spectral decomposition. In particular, we evaluate the effect of considering the hypocentral depth as an additional variable for the attenuation model, using as the target the tendency of the average stress drop to increase with depth, as observed in recent studies. We analyze the Fourier spectra of S-wave windows for about 1900 earthquakes with a magnitude above 2.5 recorded in the Ridgecrest region, southern California. Two different parameterizations of the attenuation term are implemented in the spectral decomposition, either as a function of the hypocentral distance alone or as a function of both epicentral distance and depth. The comparison of the spectral attenuation curves shows that, although the hypocentral model describes, on average, the range of values spanned by the attenuation curve for different depths, systematic differences with distance, depth, and frequency are observed. These differences are transferred to the source spectra and, in turn, to the source parameters extracted from the best-fitting ω−2 models. In particular, stress drops for events deeper than 7 km are, on average, almost double even when depth is introduced explicitly in the attenuation model. The increase of stress drop with depth is confirmed also after accounting for the increase of the shear velocity with depth, which absorbs about 30%–40% of the total increase. Moreover, a qualitative comparison with a model for the gradient of the effective normal stress confirms the reliability of the observed trend. Finally, the coherent spatial patterns shown by a simplified 2D tomographic representation of the spectral residuals highlights the impact on ground-shaking variability of the lateral variability of the crustal attenuation properties in the region.

Use of reciprocity theorem for obtaining Rayleigh wave radiation patterns

1966 ◽  
Vol 56 (4) ◽  
pp. 925-936 ◽  
Author(s):  
I. N. Gupta
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Three Dimensional ◽  
Reciprocity Theorem ◽  
Point Sources ◽  
Dimensional Case ◽  
Wave Radiation ◽  
Radiation Patterns ◽  
Homogeneous Half Space ◽  
Double Couple

abstract The reciprocity theorem is used to obtain Rayleigh wave radiation patterns from sources on the surface of or within an elastic semi-infinite medium. Nine elementary line sources first considered are: horizontal and vertical forces, horizontal and vertical double forces without moment, horizontal and vertical single couples, center of dilatation (two dimensional case), center of rotation, and double couple without moment. The results are extended to the three dimensional case of similar point sources in a homogeneous half space. Haskell's results for the radiation patterns of Rayleigh waves from a fault of arbitrary dip and direction of motion are reproduced in a much simpler manner. Numerical results on the effect of the depth of these sources on the Rayleigh wave amplitudes are shown for a solid having Poisson's ratio of 0.25.

scholarly journals Triplicated P-wave measurements for waveform tomography of the mantle transition zone

Solid Earth ◽  
2012 ◽  
Vol 3 (2) ◽  
pp. 339-354 ◽  
Author(s):  
S. C. Stähler ◽  
K. Sigloch ◽  
T. Nissen-Meyer
Keyword(s):  
Transition Zone ◽  
Epicentral Distance ◽  
Body Wave ◽  
Source Parameters ◽  
Body Waves ◽  
P Wave ◽  
Theoretical Modelling ◽  
Finite Frequency ◽  
Mantle Transition Zone ◽  
Band Limited

Abstract. Triplicated body waves sample the mantle transition zone more extensively than any other wave type, and interact strongly with the discontinuities at 410 km and 660 km. Since the seismograms bear a strong imprint of these geodynamically interesting features, it is highly desirable to invert them for structure of the transition zone. This has rarely been attempted, due to a mismatch between the complex and band-limited data and the (ray-theoretical) modelling methods. Here we present a data processing and modelling strategy to harness such broadband seismograms for finite-frequency tomography. We include triplicated P-waves (epicentral distance range between 14 and 30°) across their entire broadband frequency range, for both deep and shallow sources. We show that is it possible to predict the complex sequence of arrivals in these seismograms, but only after a careful effort to estimate source time functions and other source parameters from data, variables that strongly influence the waveforms. Modelled and observed waveforms then yield decent cross-correlation fits, from which we measure finite-frequency traveltime anomalies. We discuss two such data sets, for North America and Europe, and conclude that their signal quality and azimuthal coverage should be adequate for tomographic inversion. In order to compute sensitivity kernels at the pertinent high body wave frequencies, we use fully numerical forward modelling of the seismic wavefield through a spherically symmetric Earth.

A Monte Carlo approach to seismic hazard analysis

1999 ◽  
Vol 89 (4) ◽  
pp. 854-866 ◽  
Author(s):  
John E. Ebel ◽  
Alan L. Kafka
Keyword(s):  
Monte Carlo ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Epicentral Distance ◽  
Ground Motions ◽  
Source Parameters ◽  
Parametric Models ◽  
Earthquake Catalog ◽  
Attenuation Relations ◽  
Ground Motion Attenuation

Abstract We have developed a Monte Carlo methodology for the estimation of seismic hazard at a site or across an area. This method uses a multitudinous resampling of an earthquake catalog, perhaps supplemented by parametric models, to construct synthetic earthquake catalogs and then to find earthquake ground motions from which the hazard values are found. Large earthquakes extrapolated from a Gutenberg-Richter recurrence relation and characteristic earthquakes can be included in the analysis. For the ground motion attenuation with distance, the method can use either a set of observed ground motion observations from which estimates are randomly selected, a table of ground motion values as a function of epicentral distance and magnitude, or a parametric ground motion attenuation relation. The method has been tested for sites in New England using an earthquake catalog for the northeastern United States and southeastern Canada, and it yields reasonable ground motions at standard seismic hazard values. This is true both when published ground motion attenuation relations and when a dataset of observed peak acceleration observations are used to compute the ground motion attenuation with distance. The hazard values depend to some extent on the duration of the synthetic catalog and the specific ground motion attenuation used, and the uncertainty in the ground motions increases with decreasing hazard probability. The program gives peak accelerations that are comparable to those of the 1996 U.S. national seismic hazard maps. The method can be adapted to compute seismic hazard for cases where there are temporal or spatial variations in earthquake occurrence rates or source parameters.

scholarly journals Rayleigh wave propagation in transversely isotropic magneto-thermoelastic medium with three-phase-lag heat transfer and diffusion

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Iqbal Kaur ◽  
Parveen Lata
Keyword(s):  
Heat Transfer ◽  
Rayleigh Wave ◽  
Homogeneous Medium ◽  
Transversely Isotropic ◽  
Phase Lag ◽  
Attenuation Coefficients ◽  
Three Phase ◽  
Stress Components ◽  
And Diffusion ◽  
Penetration Depths

Abstract The present research deals with the propagation of Rayleigh wave in transversely isotropic magneto-thermoelastic homogeneous medium in the presence of mass diffusion and three-phase-lag heat transfer. The wave characteristics such as phase velocity, attenuation coefficients, specific loss, and penetration depths are computed numerically and depicted graphically. The normal stress, tangential stress components, temperature change, and mass concentration are computed and drawn graphically. The effects of three-phase-lag heat transfer, GN type-III, and LS theory of heat transfer are depicted on the various quantities. Some particular cases are also deduced from the present investigation.

scholarly journals Optimization of Gravity Wave Source Parameters for Improved Seasonal Prediction of the Quasi-Biennial Oscillation

2019 ◽  
Vol 76 (9) ◽  
pp. 2941-2962
Author(s):  
Cory A. Barton ◽  
John P. McCormack ◽  
Stephen D. Eckermann ◽  
Karl W. Hoppel
Keyword(s):  
Gravity Wave ◽  
Optimal Parameter ◽  
Forecast Error ◽  
Source Parameters ◽  
Phase Speed ◽  
Time Interval ◽  
Quasi Biennial Oscillation ◽  
Wave Source ◽  
Forecast Lead Time ◽  
Biennial Oscillation

Abstract A methodology is presented for objectively optimizing nonorographic gravity wave source parameters to minimize forecast error for target regions and forecast lead times. In this study, we employ a high-altitude version of the Navy Global Environmental Model (NAVGEM-HA) to ascertain the forcing needed to minimize hindcast errors in the equatorial lower stratospheric zonal-mean zonal winds in order to improve forecasts of the quasi-biennial oscillation (QBO) over seasonal time scales. Because subgrid-scale wave effects play a large role in driving the QBO, this method leverages the nonorographic gravity wave drag (GWD) parameterization scheme to provide the necessary forcing. To better constrain the GWD source parameters, we utilize ensembles of NAVGEM-HA hindcasts over the 2014–16 period with perturbed source parameters and develop a cost function to minimize errors in the equatorial lower stratosphere compared to analysis. Thus, we may determine the set of GWD source parameters that yields a forecast state that most closely agrees with observed QBO winds over each optimization time interval. Results show that the source momentum flux and phase speed spectrum width are the most important parameters. The seasonal evolution of optimal parameter value, specifically a robust semiannual periodicity in the source strength, is also revealed. Changes in optimal source parameters with increasing forecast lead time are seen, as the GWD parameterization takes on a more active role as QBO driver at longer forecast lengths. Implementation of a semiannually varying source function at the equator provides RMS error improvement in QBO winds over the default constant value.

scholarly journals Source Parameter of Earthquakes in Talala, Gujarat (India): An Implication towards Seismotectonic

Proceedings ◽  
2019 ◽  
Vol 24 (1) ◽  
pp. 7
Author(s):  
Sandeep Kumar Aggarwal
Keyword(s):  
Epicentral Distance ◽  
Moment Tensor ◽  
Source Parameters ◽  
Focal Depth ◽  
B Value ◽  
Complete Sequence ◽  
P Value ◽  
Centroid Moment Tensor ◽  
North East ◽  
Lateral Plane

Talala is an excellent example of triggered neo-tectonic seismicity between two dams during a monsoon. An earthquake of Mmax 5.1 on 6 November 2007 at 21.16° N; 70.54° E, with a focal depth of 4.5 km and complete sequence, was first-time recorded on the latest broadband sensor. This found a dam/monsoon-induced earthquake preceded by 18 foreshocks of 2 ≤ Mw ≤ 4.8 within 9 h 11 minute, as well as smaller shocks that may not have been recorded because of sparse network coverage. After the deployment of local mobile observatories, aftershocks of Mw ≥ 1.0, which continued for months and subsided to background seismicity after four months, were recorded. The same kind of phenomena repeated, with Mmax 5.0 on 20 October 2011 at 21.06° N; 70.50° E, focal depth 5.5 km, which implies that the potential to generate dam/monsoon-induced seismicity took nearly four years again. These phenomena continued and the sequence was recorded by a network of 10 broadband seismographs (three in the Talala area and seven at an epicentral distance of 30 to 300 km). Centroid Moment Tensor (CMT) solutions and spectral source parameters of mainshock and aftershocks are evaluated to understand the seismotectonic of the region. The CMT depicts a major strike-slip motion along East North East-West South West with a left-lateral plane at 4.5 km depth. This indicates a sympathetic fault extension of the Son-Narmada fault. The source parameters of 400 shocks of Mw 1.0 to 5.1 found seismic moment 1011 to 1016.5 N-m, source radii 120–850 meter, and a stress drop of 0.003 to 25.43 Mpa. The b-value, p-value, fractal dimension, and slip on estimated different faults. The comparison between Talala and Koyna dam-induced source parameters tries to establish a comparison of seismicity from different parts of the world.

Focal depths and source parameters of the Rocky Mountain House earthquake swarm from digital data at Edmonton

1984 ◽  
Vol 21 (10) ◽  
pp. 1105-1113 ◽  
Author(s):  
C. J. Rebollar ◽  
E. R. Kanasewich ◽  
E. Nyland
Keyword(s):  
Epicentral Distance ◽  
Source Parameters ◽  
Earthquake Swarm ◽  
Focal Depth ◽  
Rocky Mountain ◽  
Small Variation ◽  
B Value ◽  
Digital Data ◽  
The Difference ◽  
Stress Drops

Seismic records at Edmonton (EDM) and Suffield (SES) between January 1976 and February 1980 show 220 events with magnitudes less than 4 originating near Rocky Mountain House. Many of these events show well defined Sn, Sg, and Pg phases and a small variation in the difference of Sg − Sn and Sg − Pg. Analysis of the theoretical travel times using a structure determined for central Alberta yields an average focal depth of 20 ± 5 km and an average epicentral distance of 175 ± 5 km southwest of Edmonton for 40 of these events. Because Sn was not clear on the remainder, it was not possible to get focal depths for all the events.Seismic moments of 80 events with local magnitudes from 1.6 to 3.5 were found to be in the range of 6.6 ± 2 × 1018 to 7.9 ± 2 × 1020 dyn∙cm (6.6 ± 2 × 1013 to 7.9 ± 2 × 1015 N∙cm). A relationship between local magnitude and seismic moment was log (M0) = 1.3ML + 16.6. This is similar to that determined for California. Source radii, where they could be determined, were 500 ± 50 m and stress drops were 0.75 ± 0.75 bar (75 ± 75 kPa).The energy release of 263 events recorded at EDM from the Rocky Mountain House area was 5.6 × 1017 erg (5.6 × 1010 J). The b value for this earthquake swarm was 0.8, similar to that observed in other parts of western Canada.The depths of focus, the low stress drops, and the statistical similarity to other natural earthquake sequences suggest that at least part of the swarm is of a natural origin.

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