Shear Wave Velocities in Deep Soil Deposits

Ohta, Yutaka; Goto, Noriko; Shiono, Keishi; Takahashi, Hiroshi; Yamamizu, Fumio; Kurihara, Shigetoshi

doi:10.4294/zisin1948.30.4_415

Cited by 8 publications

(3 citation statements)

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“…Q S ( f ) and t * represent the frequency-dependent value of Q in the media between the two depth levels at which seismometers are installed in the seismic and engineering bedrock and the one-way time of S-waves traveling through the media, respectively. The S-wave impedance was measured at the time of the construction of the deepest borehole (Ohta et al, 1978;Yamamizu et al, 1981), and the calculated G o is 2.76 at the SHM site and 2.01 at the FCH site. The oneway time t * is estimated in this study for the time when the data windows used in estimating G( f ) were determined.…”

Section: Discussionmentioning

confidence: 99%

“…(a) Velocity structure at the SHM station, as determined by Ohta et al (1978). (b) Velocity structure at the FCH station, as determined by Yamamizu et al (1981).…”

Section: Methodsmentioning

confidence: 99%

“…2 (a). Vertically propagating S-wave velocities estimated for the Pleistocene rocks and pre-Tertiary basement using a down-hole method are 0.45 and 2.54 km/s, respectively (Ohta et al, 1978). On this basis, the seismic and engineering bedrock waves are recorded by seismometers installed at the depths of 2,300 and 200 m, respectively.…”

Section: Datamentioning

confidence: 99%

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Propagation characteristics of bedrock waves traveling from pre-Tertiary basement to engineering bedrock

Kinoshita

2007

Earth Planet Sp

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This study uses borehole array recordings to measure the propagation characteristics of bedrock waves traveling from pre-Tertiary basement (seismic bedrock) to engineering bedrock with an S-wave velocity of approximately 0.5-0.8 km/s. To avoid the destructive interference of surface-reflected down-going waves and incidence waves in seismic and engineering bedrock, borehole data recorded at sufficient depth levels are used in this study. This is the most important aspect of the fundamental basis of this study. The propagation characteristics, i.e., the transfer function, of bedrock motions for S-waves are well represented by a Butterworth-type low-pass filter model with a high corner frequency in excess of 15 Hz and a low decay rate of −3 power of frequency. The use of such a filter model is based on the concise representation of the transfer function from an engineering viewpoint. Simple one-dimensional ray theory with a plane wave approximation explains the characteristics of the model filter at low frequencies of less than approximately 5 Hz; however, one-dimensional ray theory with a plane wave approximation at high frequencies in excess of 5 Hz requires the unusual frequency characteristics of Q S −1 ( f ), which increases with increasing frequency, to explain the frequency characteristics of the model filter. These facts imply that the filter gain can be determined using the impedance ratio of seismic bedrock to engineering bedrock and the attenuation characteristics of the intervening media at low frequencies less than 5 Hz. However, the cutoff frequency and decay rate of the filter must be determined from observational data.

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Section: Discussionmentioning

confidence: 99%

“…(a) Velocity structure at the SHM station, as determined by Ohta et al (1978). (b) Velocity structure at the FCH station, as determined by Yamamizu et al (1981).…”

Section: Methodsmentioning

confidence: 99%