scholarly journals Model Experiments on Body Waves-Travel Times, Amplitudes, Wave Forms and Attenuation

1965 ◽  
Vol 13 (1) ◽  
pp. 10-33 ◽  
Author(s):  
Hideki SHIMAMURA ◽  
Ryosuke SATO
Keyword(s):  
Body Waves ◽  
Travel Times ◽  
Model Experiments ◽  
Wave Forms

scholarly journals Asymptotic analysis for dispersion relations and travel times in noise cross-correlations: spherically symmetric case

2018 ◽  
Vol 474 (2218) ◽  
pp. 20180382
Author(s):  
Tianshi Liu ◽  
Haiming Zhang
Keyword(s):  
Asymptotic Analysis ◽  
Surface Waves ◽  
Green's Functions ◽  
Green’S Functions ◽  
Dispersion Relations ◽  
Body Waves ◽  
Spherically Symmetric ◽  
Travel Times ◽  
Cross Correlations ◽  
The Cross

The cross-correlations of ambient noise or earthquake codas are massively used in seismic tomography to measure the dispersion curves of surface waves and the travel times of body waves. Such measurements are based on the assumption that these kinematic parameters in the cross-correlations of noise coincide with those in Green's functions. However, the relation between the cross-correlations of noise and Green's functions deserves to be studied more precisely. In this paper, we use the asymptotic analysis to study the dispersion relations of surface waves and the travel times of body waves, and come to the conclusion that for the spherically symmetric Earth model, when the distribution of noise sources is laterally uniform, the dispersion relations of surface waves and the travel times of SH body-wave phases in noise correlations should be exactly the same as those in Green's functions.

A study of the Earth's crust and upper mantle using travel times and spectrum characteristics of body waves

1970 ◽  
Vol 60 (6) ◽  
pp. 1921-1935
Author(s):  
B. M. Gurbuz
Keyword(s):  
Upper Mantle ◽  
Body Waves ◽  
Earth’S Crust ◽  
Travel Times ◽  
Time Data ◽  
Crust And Upper Mantle ◽  
Contour Maps ◽  
Spectrum Characteristics ◽  
Earth's Crust ◽  
Early Rise

Abstract The aim of this paper is to investigate the velocity distribution and structure of the Earth's crust and upper mantle from the close collaboration of theory and experimental results of travel times and spectrum characteristics of body waves. The interpretation was based on 38 seismic records which were obtained from the “Project Early Rise” experiment during July 1966. The results refer to the area bounded by latitudes 49°W and 51°30′ and longitudes 93°W and 98°W. A least-squares analysis of the travel-time data was made and the uncertainties of the slopes, intercept times, and corresponding velocities were determined. The observed wide-angle reflections were used to calculate the root mean square velocities applying the T2 - X2 method. Depth calculations for the velocity discontinuities and seismic depth contour maps were made. A model was constructed, and the validity of the proposed new model was tested by comparing the observed travel times, spectrum-amplitude ratios, and relative phase shifts of body waves with theoretically expected values. Evidence is given for three discontinuities in the Earth's crust with velocities of 6.11 ± 0.01 km/sec, 6.8 ± 0.08 km/sec, and 7.10 ± 0.04 km/sec at average depths 18 ± 2 km and 25.5 ± 0.9 km. Velocities in the uppermost part of the mantle were determined as 7.90 ± 0.05 km/sec and 8.48 ± 0.05 km/sec with interfaces at the average depths of 34 ± 1 km, and 47 ± 1 km, respectively.

scholarly journals The February 9, 1971 San Fernando earthquake: A study of source finiteness in teleseismic body waves

1978 ◽  
Vol 68 (1) ◽  
pp. 1-29 ◽  
Author(s):  
Charles A. Langston
Keyword(s):  
Near Field ◽  
Dislocation Line ◽  
Strong Motion ◽  
Body Waves ◽  
P Waves ◽  
Long Period ◽  
Short Period ◽  
Wave Forms ◽  
San Fernando ◽  
The Time Domain

abstract Teleseismic P, SV, and SH waves recorded by the WWSS and Canadian networks from the 1971 San Fernando, California earthquake (ML = 6.6) are modeled in the time domain to determine detailed features of the source as a prelude to studying the near and local field strong-motion observations. Synthetic seismograms are computed from the model of a propagating finite dislocation line source embedded in layered elastic media. The effects of source geometry and directivity are shown to be important features of the long-period observations. The most dramatic feature of the model is the requirement that the fault, which initially ruptured at a depth of 13 km as determined from pP-P times, continuously propagated toward the free surface, first on a plane dipping 53°NE, then broke over to a 29°NE dipping fault segment. This effect is clearly shown in the azimuthal variation of both long period P- and SH-wave forms. Although attenuation and interference with radiation from the remainder of the fault are possible complications, comparison of long- and short-period P and short-period pP and P waves suggest that rupture was initially bilateral, or, possibly, strongly unilateral downward, propagating to about 15 km depth. The average rupture velocity of 1.8 km/sec is well constrained from the shape of the long-period wave forms. Total seismic moment is 0.86 × 1026 dyne-cm. Implications for near-field modeling are drawn from these results.

Investigation of a method for determining stress accumulation at depth—II

1969 ◽  
Vol 59 (1) ◽  
pp. 43-58
Author(s):  
Joseph D. Eisler
Keyword(s):  
Field Experiments ◽  
San Andreas Fault ◽  
Body Waves ◽  
Travel Times ◽  
Compressional Waves ◽  
San Andreas ◽  
Path Lengths ◽  
Stress Accumulation

Abstract The second of two seismic field experiments designed to study the precision with which the arrival of compressional body waves could be timed over paths up to 42 km in length was performed seven months after the first at the same location in the Gabilan Range near Salinas, California. Results of the second experiment show that the timing of the compressional waves could be carried out to the same order of precision as in the first experiment, i.e., to ±1 msec. In addition, the travel times over certain path lengths increased by about 6 msec within the intervening period. This observation is discussed in terms of the possible release of stress at depth in the region adjacent to the San Andreas Fault.

Body waves and ray theory – travel times

2021 ◽  
pp. 339-362
Author(s):  
Charles J. Ammon ◽  
Aaron A. Velasco ◽  
Thorne Lay ◽  
Terry C. Wallace
Keyword(s):  
Body Waves ◽  
Ray Theory ◽  
Travel Times

Travel times of body waves in the moon

1970 ◽  
Vol 60 (1) ◽  
pp. 63-78 ◽  
Author(s):  
Yosio Nakamura ◽  
Gary V. Latham
Keyword(s):  
Large Amplitude ◽  
Body Waves ◽  
Central Core ◽  
Travel Times ◽  
The Moon ◽  
Shadow Zone ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
Velocity Zone

abstract Travel times and amplitudes of body waves in lunar models have been computed. The effect of a low-velocity zone upon the travel times and amplitudes of body waves is likely to be small unless the condition for the existence of a shadow zone at short to moderate epicentral distances is nearly satisfied. The PKP phase from a possible central core of the moon is likely to have a large amplitude in the area opposite to the epicenter.

The earthquake volume

1970 ◽  
Vol 60 (5) ◽  
pp. 1479-1489
Author(s):  
Seweryn J. Duda
Keyword(s):  
Observational Data ◽  
Critical Strain ◽  
Focal Depth ◽  
Body Waves ◽  
P Wave ◽  
Seismic Events ◽  
Travel Times ◽  
Calibration Curves ◽  
Wave Travel

Abstract A method is presented enabling one to estimate the volume of seismic events with all possible magnitudes and focal depths. The underlying observational data are either the travel times of body waves, or the equivalent magnitude calibration curves for body waves, if the absorption of body waves is neglected. The method is applied to the newest P-wave travel times. The distance from the focus to a point at which a given critical strain existed during the event is computed. The volume within strains larger than the critical prevailed during the event is obtained as a function of magnitude and focal depth. The volume so found is in agreement with a previous determination of the earthquake volume as a function of magnitude.

scholarly journals t* for S waves with a continental ray path

1978 ◽  
Vol 68 (4) ◽  
pp. 1013-1030
Author(s):  
L. J. Burdick
Keyword(s):  
Body Wave ◽  
Body Waves ◽  
P Wave ◽  
Lateral Asymmetry ◽  
Deep Earthquake ◽  
Data Set ◽  
S Waves ◽  
Short Period ◽  
Wave Forms ◽  
Ray Path

abstract The purpose of this study was to determine t* for S waves with ray paths under the continental United States. The data set consists of long- and short-period body waves from the Borrego Mountain earthquake as observed in the northeastern U.S. The P wave forms are dominated by the sP phase and the SH wave forms by the sS. It is assumed that there are no losses in pure compression so that the relative attenuation rate of P and S waves is known. The initial source radiation is determined from the sP phase and the value of tβ* from the spectral content of the S wave. The results indicate that tβ* is 5.2 ± 0.7 sec along this ray path. Long- and short-period body waves from some deep South American events are used to test for lateral asymmetry of the Q distribution under the U.S. No lateral amplitude variation exists in this data, but this result is difficult to correlate with many previous results. The t°* value for a 600-km deep earthquake appears to be about 3 sec. A comparison of these values with values computed from current models of the Earth's Q distribution indicates that the models are slightly too high in Q overall and that more of the total body-wave attenuation occurs above 600 km than is indicated by the models.

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