Laboratory Study on Scattering Characteristics of Shear Waves in Rock Samples

Fukushima, Yo; Nishizawa, Osamu; Sato, Haruo; Ohtake, Masakazu

doi:10.1785/0120020074

Cited by 45 publications

(32 citation statements)

References 41 publications

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“…Assigning the P-wave velocity of each mineral to appropriate locations on a surface photo image of a granite sample, Sivaji et al (2002) and Fukushima et al (2003) made 1-D velocity distributions. Granite is composed of feldspar, quartz, and biotite.…”

Section: Acf Of Velocity Inhomogeneity Revealed From Well-logs and Romentioning

confidence: 99%

Seismic Wave Propagation and Scattering in the Heterogeneous Earth : Second Edition

Sato¹,

Fehler²,

Maeda³

2012

458

385

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Scattering due to randomly distributed small-scale heterogeneities in the earth significantly changes seismic waveforms of local earthquakes especially for short periods. Scattering excites long lasting coda waves after the direct arrival and broadens the apparent duration of oscillation with increasing travel distance much longer than the source duration time. Models of propagation through deterministic structures such as those with horizontally uniform velocity layers cannot explain those observed phenomena. Our goal in writing this book is to put a focus on the phenomena of seismic wave scattering by distributed heterogeneities in the earth, especially in the lithosphere, where stochastic treatment is essential to describe both heterogeneous media and wave propagation through them. Stochastic approaches and deterministic approaches are complementary for the construction of a unified image of the earth's structure.Keiiti Aki was a distinguished pioneer who extensively developed various stochastic methods for short-period seismology. His strong encouragement and continuous support for us were essential in motivating us to write the first edition of this book. Before Kei passed away in 2005, he kindly cited our book when he argued for the importance of the study on seismic wave scattering caused by small-scale heterogeneity in his letter to V. I. Keilis-Borok, ". . . To a geodynamicist, the earth's property is smoothly varying within bodies bounded by large-scale interfaces. Most seismologists also belong to this "smooth earth club," because once you start with an initial model of smooth earth your data usually do not require the addition of smallscale heterogeneity to your initial model. As summarized well in a recent book by Sato and Fehler (1998), the acceptance of coda waves in the data set is needed for the acceptance of small-scale seismic heterogeneity of the lithosphere. There are an increasing number of seismologists who accept it, forming the "rough earth club." I believe that you are also a member of the rough earth club, judging from the emphasis on the hierarchical heterogeneity of the lithosphere. . . . "(Aki 2009).The first edition of this book was fortunately accepted in the geophysical community as a textbook, especially for graduate students. Furthermore it has been often cited in the physics community since this book introduced various aspects of wave scattering in real heterogeneous media. During the decade following the vii viii Preface to the Second Edition publication of the first edition, there were developments in stochastic methods and analyses focusing on seismogram envelopes. Radiative transfer theory has been used not only for the study of coda envelopes but also for the analysis of whole seismogram envelopes. These studies made it possible to resolve the spatial variation of scattering strength. There have been developments in the statistical description of wave propagation in random media that reliably predict the delay of peak amplitude from the onset and the broadening of seismogr...

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Section: Acf Of Velocity Inhomogeneity Revealed From Well-logs and Romentioning

confidence: 99%

Seismic Wave Propagation and Scattering in the Heterogeneous Earth : Second Edition

Sato¹,

Fehler²,

Maeda³

2012

458

385

View full text Add to dashboard Cite

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“…The maps are then converted to P-velocity maps by assigning velocity values to the minerals (Fukushima 2000;Spetzler et al 2001). Microstructure images of the granitic rocks are obtained with 600-dpi (dot per inch) colour data.…”

Section: Random Medium Analysismentioning

confidence: 99%

“…The colour images are converted to tri-colour images to identify the three minerals: white, gray and black colour corresponding to plagioclase, quartz and biotite, respectively. However, the measurements of waveforms in different directions suggest that the effect of cracks on observed waveforms is not strong for frequencies less than 1 MHz (Nishizawa et al 1997;Fukushima 2000). The maps are then converted to P-velocity maps by assigning velocity values to the minerals (Fukushima 2000;Spetzler et al 2001).…”

Section: Random Medium Analysismentioning

confidence: 99%

A physical-model study of the statistics of seismic waveform fluctuations in random heterogeneous media

Sivaji

Nishizawa

Kitagawa

et al. 2002

Geophysical Journal International

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SUMMARY Using laboratory‐scale physical models, we studied seismic waveform fluctuation in 3‐D heterogeneous media, and evaluated the effects of short‐wavelength random heterogeneity on seismic waves. We made two series of experiments: (1) waves are excited by the same source signal and propagate through three kinds of granitic rocks with different scales of heterogeneity, and (2) waves are excited by different frequencies but propagating through the same rock. A compression‐mode piezoelectric transducer was attached to one side of the block, and the waveforms were measured at a 10 mm radius circular array with a 2 ° spacing, located on the other side. 180 waveforms are obtained at equal source–receiver distances with an equal wave radiation from the source. The source signals are one‐ or two‐cycle sine‐wave pulse with 0.5 MHz for different heterogeneities, and 0.25, 0.5, 1 and 2 MHz for the same heterogeneity. Waveforms were recorded by using a system equipped with a laser Doppler vibrometer as a sensor of elastic waves. The rock heterogeneities were investigated as the 1‐D velocity fluctuations obtained from the 2‐D microstructure images of the rock. By applying the exponential autocorrelation function, heterogeneities in the three rocks are characterized by similar fluctuation intensities (7.9–9.3 per cent) but different scale lengths ranging from 0.22 to 0.92 mm. We calculated the spatial correlation of waveforms, the correlation between an averaged waveform and observed waveforms, the energy partition with respect to lapse time, and the statistical distributions of the waveform parameters: correlation coefficients, traveltimes of P wave, and the log values of the P‐phase energy. Correlation of waveforms, energy partition and statistical parameters of waveforms are investigated as a function of the normalize scale parameter ka: the product of wave number and the characteristic scale length of heterogeneity. We found that waveform parameters change the trends at ka∼0.2–0.3. When ka exceeds 0.2–0.3, scattered waves become strong and waveforms become more complicated. This may indicate a transition from an equivalent homogeneous medium to a scattering medium for seismic waves propagating through random heterogeneous medium.

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“…To separate P and S waves, these authors performed measurements in two directions and then found projections of the displacement onto directions perpendicular and parallel to the surface. Fukushima et al (2003) used LDI to investigate polarisation of the shear waves in rock samples. The main advantage of using LDI in comparison with piezoelectric transducers is that the area of the measurement is much smaller than the wavelength, and that the full particle velocity vector can be recorded.…”

Section: Introductionmentioning

confidence: 99%