Mean free path of S-waves under the Kanto district of Japan.

Sato, Haruo

doi:10.4294/jpe1952.26.185

Cited by 75 publications

(26 citation statements)

References 8 publications

(12 reference statements)

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“…Later, coda waves were thought to offer a useful seismological tool for the quantitative estimation of the strength of random heterogeneity (Aki and Chouet 1975;Sato 1978). As seismometers were placed in boreholes where ambient seismic noise was greatly reduced compared to that on the ground surface and as the onset of digital seismic network allowed dynamic range to be increased, envelopes of entire seismograms including both the maximum amplitude portion and the coda portion were recorded and modeled to learn more about the random heterogeneity of the earth's lithosphere by using frequencies in the range of 1-30 Hz.…”

Section: Scattering Of Seismic Wavesmentioning

confidence: 99%

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

Sato¹,

Fehler²,

Maeda³

2012

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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: Scattering Of Seismic Wavesmentioning

confidence: 99%

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

Sato¹,

Fehler²,

Maeda³

2012

Self Cite

458

385

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show abstract

“…(12) is modified as (13) The scattering coefficient g0 and QS are derived from a and b, Frequency dependence of the total scattering coefficient derived from the amplitude ratio between S-and coda waves in the western Nagano region (solid circles). The extent of the scattering coefficients estimated in Kanto (Aki, 1980a;Sato, 1978) and Kanto-Tokai (Fehler et al, 1992) region is expressed by rectangles. The location of these regions is shown in Fig.…”

Section: One-dimensional Qs Structurementioning

confidence: 99%

Dependence of Coda Q on Frequency and Lapse Time in the Western Nagano Region, Central Japan.

Kosuga

1992

J,Phys,Earth

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We have investigated the dependence of coda Q (QC) on frequency and lapse time using the data observed at short hypocentral distances (1-23 km) over a wide frequency range (1-64 Hz). QC was determined by applying a single isotropic scattering model to the bandpass-filtered seismograms from aftershocks of the 1984 Western Nagano Prefecture, Earthquake. QC depends on frequency, f in Hz, according to a power law, QC=Q0fn. We also found a strong dependence of QC on lapse time, in particular, for short lapse times less than 10 s. This lapse time dependence is characterized by an increase in Q0 and a decrease in n with lapse time. We interpreted this observation as indication of depth variation of QS and estimated a crustal model of one-dimensional QS structure from QC measured at various lapse times. The model exposes low QS in a surface layer and a significant increase in QS with depth in the upper 2 km of the crust. QS in the uppermost crust is compatible with that measured at a deep borehole in the Kanto Plain, central Japan. However, we cannot attribute the lapse time dependence of QC to the sole effect of depth, variation of QS, because QC calculated from the QS model shows more gradual increase than the observation. The scattering coefficient (g0) estimated from the amplitude ratio of S-and coda waves, as well as QS calculated from the energy flux model, suggest a contribution of multiple scattering to the lapse time dependence for long lapse times. For short lapse times, on the other hand, depth variation of g0, as indicated by the change in n with lapse time, is possibly responsible for the sharp increase in QC with lapse time. Thus the apparent lapse time dependence of QC is caused by a combination of depth variation of QS and g0, and multiple scattering effect.

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“…On the basis of travel time tomography Sharma (2008) showed that the crust in the Garhwal and Kumaun area is highly heterogeneous. Sato (1978) and Pulli (1984) have shown that the scatterers responsible for the generation of coda waves are generally assumed to be distributed over the surface area of an ellipsoid which can be estimated using the following equation: where x and y are the surface co-ordinates, R is the hypocentral distance, v is the velocity of S-wave and t c is the average lapse time, respectively. We have used S-wave velocity of 3.6 km/s and average lapse time duration t c = 2t s + W/2.…”

Section: Frequency Dependence Of Coda Qmentioning

confidence: 99%

Lapse time and frequency-dependent attenuation characteristics of Kumaun Himalaya

Singh

Bharathi

Chadha

2012

Journal of Asian Earth Sciences

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Mean free path of S-waves under the Kanto district of Japan.

Cited by 75 publications

References 8 publications

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

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

Dependence of Coda Q on Frequency and Lapse Time in the Western Nagano Region, Central Japan.

Lapse time and frequency-dependent attenuation characteristics of Kumaun Himalaya

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