scholarly journals Estimation of radiated energy using the KiK-net downhole records—old method for modern data

2020 ◽  
Vol 221 (2) ◽  
pp. 1029-1042 ◽  
Author(s):  
Hiroo Kanamori ◽  
Zachary E Ross ◽  
Luis Rivera
Keyword(s):  
Site Response ◽  
Source Model ◽  
Synthetic Seismograms ◽  
S Wave ◽  
P Waves ◽  
S Waves ◽  
Radiated Energy ◽  
Time Integral ◽  
Magnitude Range ◽  
Significant Difference

SUMMARY We use KiK-net (NIED) downhole records to estimate the radiated energy, ER, of 29 Japanese inland earthquakes with a magnitude range from Mw = 5.6 to 7.0. The method is based on the work of Gutenberg and Richter in which the time integral of S-wave ground-motion velocity-squared is measured as a basic metric of the radiated energy. Only stations within a distance of 100 km are used to minimize complex path and attenuation effects. Unlike the teleseismic method that uses mainly P waves, the use of S waves which carry more than 95 per cent of the radiated energy allows us to obtain robust results. We calibrate the method using synthetic seismograms to modernize and improve the Gutenberg–Richter method. We compute synthetic seismograms for a source model of each event with a given source function (i.e. known ER), the actual mechanism and the source-station geometry. Then, we compare the given ER with the computed energy metric to correct for the unknown effect of wave propagation and the mechanism. The use of downhole records minimizes the uncertainty resulting from the site response. Our results suggest that the currently available estimates of ER from teleseismic data are probably within a factor of 3, on average, of the absolute value. The scaled energy eR ( = ER/M0) is nearly constant at about 3 × 10−5 over a magnitude range from Mw = 5.6 to 7.0 with a slight increasing trend with Mw. We found no significant difference in eR between dip-slip and strike-slip events.

Numerical simulation of azimuthal acoustic logging in a borehole penetrating a rock formation boundary

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. D283-D291 ◽  
Author(s):  
Peng Liu ◽  
Wenxiao Qiao ◽  
Xiaohua Che ◽  
Xiaodong Ju ◽  
Junqiang Lu ◽  
...  
Keyword(s):  
Domain Model ◽  
P Wave ◽  
S Wave ◽  
Angle Variation ◽  
P Waves ◽  
Acoustic Logging ◽  
S Waves ◽  
Rock Formation ◽  
Logging Tool ◽  
Difference Time

We have developed a new 3D acoustic logging tool (3DAC). To examine the azimuthal resolution of 3DAC, we have evaluated a 3D finite-difference time-domain model to simulate a case in which the borehole penetrated a rock formation boundary when the tool worked at the azimuthal-transmitting-azimuthal-receiving mode. The results indicated that there were two types of P-waves with different slowness in waveforms: the P-wave of the harder rock (P1) and the P-wave of the softer rock (P2). The P1-wave can be observed in each azimuthal receiver, but the P2-wave appears only in the azimuthal receivers toward the softer rock. When these two types of rock are both fast formations, two types of S-waves also exist, and they have better azimuthal sensitivity compared with P-waves. The S-wave of the harder rock (S1) appears only in receivers toward the harder rock, and the S-wave of the softer rock (S2) appears only in receivers toward the softer rock. A model was simulated in which the boundary between shale and sand penetrated the borehole but not the borehole axis. The P-wave of shale and the S-wave of sand are azimuthally sensitive to the azimuth angle variation of two formations. In addition, waveforms obtained from 3DAC working at the monopole-transmitting-azimuthal-receiving mode indicate that the corresponding P-waves and S-waves are azimuthally sensitive, too. Finally, we have developed a field example of 3DAC to support our simulation results: The azimuthal variation of the P-wave slowness was observed and can thus be used to reflect the azimuthal heterogeneity of formations.

A computer program for focal mechanism determination combining P and S wave data

1969 ◽  
Vol 59 (2) ◽  
pp. 503-519
Author(s):  
Agustin Udias ◽  
Dieter Baumann
Keyword(s):  
Computer Program ◽  
Focal Mechanism ◽  
Total Error ◽  
Source Model ◽  
Polarization Angle ◽  
S Wave ◽  
Period Range ◽  
S Waves ◽  
Double Couple ◽  
The Relationship

abstract A computer program has been developed to find the orientation of a double couple source model for the mechanism of an earthquake which best satisfies the data from P and S waves. The relationship between the two axes of the solution given by the equations for the polarization angle of S is used in order to rapidly find the orientation of the source model for which a total error value involving the error of S and P data is a minimum. The program gives best results for data from homogeneous instruments of similar period range. Solutions for three earthquakes, selected because of the orientation of the source, are presented and the reliability of their solutions under ideal conditions is discussed.

An analytical solution to separate P‐waves and S‐waves in VSP wavefields

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 955-967 ◽  
Author(s):  
Hiroshi Amano
Keyword(s):  
Analytical Solution ◽  
Formal Solution ◽  
Seismic Profile ◽  
Synthetic Seismograms ◽  
Third Order ◽  
P Waves ◽  
Practical Applications ◽  
S Waves ◽  
The Third ◽  
Z Domain

An analytical solution to separate P‐waves and S‐waves in vertical seismic profile (VSP) wavefields is derived using combinations of certain terms of the formal solution for forward VSP modeling. Some practical applications of this method to synthetic seismograms and field data are investigated and evaluated. Little wave distortion is recognized, and the weak wavefield masked by dominant wavetrains can be extracted with this method. The decomposed wavefield is expressed in the frequency‐depth (f-z) domain as a linear combination of up to the third‐order differential of traces, which is approximated by trace differences in the practical separation process. In general, five traces with single‐component data are required in this process, but the same process is implemented with only three traces in the acoustic case. Two‐trace extrapolation is applied to each edge of the data gather to enhance the accuracy of trace difference. Since the formulas are developed in the f-z domain, the influence of anelasticity can be taken into account, and the calculation is carried out fast enough with the benefit of the fast Fourier transform (FFT).

A two‐layer stacking procedure to enhance converted waves

Geophysics ◽  
1993 ◽  
Vol 58 (7) ◽  
pp. 997-1001 ◽  
Author(s):  
B. L. N. Kennett
Keyword(s):  
Lower Layer ◽  
Effective Means ◽  
Water Layer ◽  
Physical Models ◽  
S Wave ◽  
P Waves ◽  
S Waves ◽  
Receiver Array ◽  
Sea Bed ◽  
Layer Stacking

For marine seismic sources quite efficient conversion of P‐waves to S‐waves can occur at hard seafloors, e.g., carbonate horizons in tropical waters. The S‐waves are reflected back from structures at depth and are reconverted to P‐waves in the water before detection by the receiver array. Such PSSP reflections can carry useful information on the structure beneath the sea bed but are most significant at large offsets and so are not easily stacked with a conventional normal moveout (NMO) procedure based on a hyperbolic time trajectory. A two‐layer stacking procedure that separates the water layer from the region below the seafloor provides a very effective means of extracting the PSSP arrivals, but also works well for P‐waves. There is no direct analytic form for the stacking trajectories but they can be calculated quite efficiently numerically. A further advantage is that the stacking velocity for S‐waves in the lower layer can be interpreted directly in terms of S‐wave propagation, so that S‐wave interval velocities can be found. Stacking procedures based on such simple physical models are likely to be useful in other cases where attention needs to be focused on a particular aspect of the wavefield.

Thin-bed prestack spectral inversion

Geophysics ◽  
2009 ◽  
Vol 74 (4) ◽  
pp. R49-R57 ◽  
Author(s):  
J. Germán Rubino ◽  
Danilo Velis
Keyword(s):  
Time Window ◽  
A Priori ◽  
Amplitude Spectrum ◽  
Wavelet Spectrum ◽  
Model Parameters ◽  
Data Sets ◽  
S Wave ◽  
P Waves ◽  
S Waves ◽  
Zero Offset

Prestack seismic data has been used in a new method to fully determine thin-bed properties, including the estimation of its thickness, P- and S-wave velocities, and density. The approach requires neither phase information nor normal-moveout (NMO) corrections, and assumes that the prestack seismic response of the thin layer can be isolated using an offset-dependent time window. We obtained the amplitude-versus-angle (AVA) response of the thin bed considering converted P-waves, S-waves, and all the associated multiples. We carried out the estimation of the thin-bed parameters in the frequency (amplitude spectrum) domain using simulated annealing. In contrast to using zero-offset data, the use of AVA data contributes to increase the robustness of this inverse problem under noisy conditions, as well as to significantly reduce its inherent nonuniqueness. To further reduce the nonuniqueness, and as a means to incorporate a priori geologic or geophysical information (e.g., well-log data), we imposed appropriate bounding constraints to the parameters of the media lying above and below the thin bed, which need not be known accurately. We tested the method by inverting noisy synthetic gathers corresponding to simple wedge models. In addition, we stochastically estimated the uncertainty of the solutions by inverting different data sets that share the same model parameters but are contaminated with different noise realizations. The results suggest that thin beds can be characterized fully with a moderate to high degree of confidence below tuning, even when using an approximate wavelet spectrum.

Reflection and refraction of elastic waves at a corrugated interface

1966 ◽  
Vol 56 (1) ◽  
pp. 201-221
Author(s):  
Shuzo Asano
Keyword(s):  
Wave Amplitude ◽  
Normal Incidence ◽  
P Wave ◽  
Irregular Waves ◽  
Angle Of Incidence ◽  
S Wave ◽  
Reflected Waves ◽  
S Waves ◽  
Significant Difference ◽  
Almost All

abstract The effect of a corrugated interface on wave propagation is considered by using the method that was first applied to acoustical gratings by Rayleigh. The problem is what happens when a plane P wave is incident on a corrugated interface that separates two semi-infinite media. As is well known, there are irregular (scattered) waves as well as regular waves. By assuming both the amplitude and the slope of a corrugated interface to be small, quantities of the order of the square of corrugation amplitude are taken into account. In the case of normal incidence for three models considered, the effect of corrugation on reflection is larger than the effect of corrugation on refraction; the amplitude of the regularly reflected waves decreases, and that of the regularly refracted waves and of the irregular waves increases, as the corrugation amplitude becomes larger. Generally, the larger the velocity contrast, the larger the variation of wave amplitude with the wavelength and the amplitude of corrugation. The S wave component generally becomes larger as the wavelength of corrugation becomes smaller. Boundary waves exist, depending upon the ratio of wavelength of corrugation to that of the incident wave. For a specified interface, it is possible that there is a significant difference in wave amplitude as a function of the elastic constants. In the case of oblique incidence, computation was carried out for angles of incidence smaller than 15° for one model. For these small angles of incidence, almost all results for the case of normal incidence still hold. Furthermore, it can be concluded that the effect of the angle of incidence on reflected S waves is larger than for the other waves and that large differences in the amplitudes of waves at different angles of incidence may be expected for the irregular waves.

A site effect study in Acapulco, Guerrero, Mexico: Comparison of results from strong-motion and microtremor data

1992 ◽  
Vol 82 (2) ◽  
pp. 642-659 ◽  
Author(s):  
Carlos Gutierrez ◽  
Shri Krishna Singh
Keyword(s):  
Seismic Waves ◽  
Site Response ◽  
Nonlinear Behavior ◽  
Strong Motion ◽  
Site Effect ◽  
Seismic Gap ◽  
S Wave ◽  
Data Set ◽  
S Waves ◽  
The City

Abstract The city of Acapulco is located near or above the mature seismic gap of Guerrero along the Mexican subduction zone. With the purpose of studying the character of strong ground motion on soft sites, four digital accelerographs have been installed in the city on such sites. These instruments have been in operation since 1988. Two additional instruments, part of the Guerrero Accelerograph Array, are located on hard sites in the area. One of these, VNTA, has been in operation since 1985 and the other, ACAN, since 1989. These stations have recorded several earthquakes. We use data from eight events (4.2 ≤ M ≤ 6.9) to study spectral amplification of seismic waves at the soft sites with respect to VNTA. The S waves are amplified by a factor of 6 to 25 at the soft sites in a fairly broad range of frequencies; both the amplification and the frequency band over which it occurs depend upon the site. Although the largest earthquake in our data set (M = 6.9) gave rise to a peak horizontal acceleration exceeding 0.3 g at one of the soft sites, no clear evidence of nonlinear behavior of the subsoil is found. Spectral amplifications of S-wave coda are very similar to those of S waves. We also measured microtremors at the strong-motion sites. The microtremor spectra were interpreted, using reasonable assumptions, to test the feasibility of this technique in reproducing the spectral amplifications observed during earthquakes. Our results show that only a rough estimate of site response can be obtained from this technique, at least in Acapulco; caution is warranted in its use elsewhere.

The partition of radiated energy between P and S waves

1984 ◽  
Vol 74 (2) ◽  
pp. 361-376
Author(s):  
John Boatwright ◽  
Jon B. Fletcher
Keyword(s):  
Wave Energy ◽  
Body Wave ◽  
Focal Mechanisms ◽  
The Body ◽  
Body Waves ◽  
P Wave ◽  
Corner Frequency ◽  
S Wave ◽  
S Waves ◽  
Radiated Energy

Abstract Seventy-three digitally recorded body waves from nine multiply recorded small earthquakes in Monticello, South Carolina, are analyzed to estimate the energy radiated in P and S waves. Assuming Qα = Qβ = 300, the body-wave spectra are corrected for attenuation in the frequency domain, and the velocity power spectra are integrated over frequency to estimate the radiated energy flux. Focal mechanisms determined for the events by fitting the observed displacement pulse areas are used to correct for the radiation patterns. Averaging the results from the nine events gives 27.3 ± 3.3 for the ratio of the S-wave energy to the P-wave energy using 0.5 〈Fi〉 as a lower bound for the radiation pattern corrections, and 23.7 ± 3.0 using no correction for the focal mechanisms. The average shift between the P-wave corner frequency and the S-wave corner frequency, 1.24 ± 0.22, gives the ratio 13.7 ± 7.3. The substantially higher values obtained from the integral technique implies that the P waves in this data set are depleted in energy relative to the S waves. Cursory inspection of the body-wave arrivals suggests that this enervation results from an anomalous site response at two of the stations. Using the ratio of the P-wave moments to the S-wave moments to correct the two integral estimates gives 16.7 and 14.4 for the ratio of the S-wave energy to the P-wave energy.

Shear waves, multiple reflections, and converted waves found by a deep vertical wave test (vertical seismic profiling)

Geophysics ◽  
1980 ◽  
Vol 45 (9) ◽  
pp. 1373-1411 ◽  
Author(s):  
C. C. Lash
Keyword(s):  
Traveling Waves ◽  
Wave Energy ◽  
S Wave ◽  
Multiple Reflections ◽  
P Waves ◽  
S Waves ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Converted Waves ◽  
Set Up

Evidence that shear (S) waves are much more important in seismic surveys than currently believed was found in each of two deep well tests conducted some time ago. Wave tests were recorded along vertical lines, following procedures which are now designated “vertical seismic profiling.” The results may be divided into (1) evidence that shear (S) waves are produced by in‐hole dynamite charges and by the resulting compressional (P) waves, and (2) evidence that the S‐waves subsequently produce P‐waves. The proof of S‐wave production is quite conclusive. Even if we say that only P‐waves are set up in the immediate vicinity of the shot, some S‐waves are then generated within a radius of 10 to 100 ft to form what we will call a direct or “source S wave.” Other S‐waves are set up by conversion of P‐wave energy to S‐wave energy at interfaces hundreds and thousands of feet from the dynamite charge. In contrast to the P to S conversion, the evidence for S to P conversion is less conclusive. The source S‐wave generated near the shot was found to have a long‐period character, with many cycles which are believed to be controlled by the layering near the shot. The PS converted waves, which appear later, resemble the P‐waves that produce them. The interference to primary reflections by multiple reflections and/or converted waves produces complex signals at points deep in the well which require directional discrimination to separate up‐traveling waves from down‐traveling waves.

scholarly journals Comparison of recent S-wave indicating methods

2018 ◽  
Vol 29 ◽  
pp. 00019
Author(s):  
Katarzyna Hubicka ◽  
Jakub Sokolowski
Keyword(s):  
Real Data ◽  
The Body ◽  
Body Waves ◽  
Identification Accuracy ◽  
P Wave ◽  
S Wave ◽  
P Waves ◽  
S Waves ◽  
Mode Decomposition ◽  
Wave Arrival

Seismic event consists of surface waves and body waves. Due to the fact that the body waves are faster (P-waves) and more energetic (S-waves) in literature the problem of their analysis is taken more often. The most universal information that is received from the recorded wave is its moment of arrival. When this information is obtained from at least four seismometers in different locations, the epicentre of the particular event can be estimated [1]. Since the recorded body waves may overlap in signal, the problem of wave onset moment is considered more often for faster P-wave than S-wave. This however does not mean that the issue of S-wave arrival time is not taken at all. As the process of manual picking is time-consuming, methods of automatic detection are recommended (these however may be less accurate). In this paper four recently developed methods estimating S-wave arrival are compared: the method operating on empirical mode decomposition and Teager-Kaiser operator [2], the modification of STA/LTA algorithm [3], the method using a nearest neighbour-based approach [4] and the algorithm operating on characteristic of signals’ second moments. The methods will be also compared to wellknown algorithm based on the autoregressive model [5]. The algorithms will be tested in terms of their S-wave arrival identification accuracy on real data originating from International Research Institutions for Seismology (IRIS) database.

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