S-wave velocity measurement in deep soil deposit and bedrock by means of an elaborated down-hole method

Ohta, Yukitaka; Goto, Noriko; Yamamizu, Fumio

doi:10.1016/0148-9062(81)90353-3

Cited by 5 publications

(8 citation statements)

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“…Since the P times contain small unknown errors that are much less than those in the S-P times, straight lines were fitted through the data sets using the maximum likelihood method of Bartlett (1949). is about 1.7, but for unconsolidated sediments the ratio is usually higher and may be as high as 4 or more (Ohta et al 1980). The ratio of the S to the P travel time should therefore be larger at short distances, since the fraction of the path length within the overburden is larger for the shear wave.…”

Section: Analysis Of S-p Versus P Timesmentioning

confidence: 96%

On the Generation of P and S Wave Energy in Crystalline Rocks*

Wright¹,

Johnson²

1982

Geophysical Prospecting

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A seismic source consisting of a 700 kg weight that could be dropped vertically or projected down a ramp inclined at 45" to the vertical was tested as a source of P, SV and SH waves within a crystalline rock body at Chalk River, Ontario. The seismic energy was recorded by arrays of both horizontal and vertical-component geophones at distances between 30 and 600 m from the source, which was operated over glacial overburden varying in thickness from less than a meter to a few tens of meters. Seismic energy was more efficiently generated when the overburden thickness was at least several meters. The signals identified visually as S are generally true S, though some may be the converted wave PS. The SV amplitudes are generally larger than those of P, regardless of the type of shot, while the signal frequencies are roughly 60 Hz and 90 Hz, respectively. The horizontal-component seismograms for the inclined shots showed no evidence of SH polarization, and the SH amplitudes were only rarely enhanced relative to P and SV amplitudes on changing from vertical to inclined shots. These unexpected results are attributed to the combined effect of the high velocity and density contrasts and the irregularity of the boundary between the glacial overburden and the rock body.

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Section: Analysis Of S-p Versus P Timesmentioning

confidence: 96%

On the Generation of P and S Wave Energy in Crystalline Rocks*

Wright¹,

Johnson²

1982

Geophysical Prospecting

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“…The authors OHTA et al, 1980), on the basis of the directly measured S-wave velocites, computed the remarkable effect of deep soil deposits upon the amplification of seismic S waves. They suggested that the effect of deep soil deposits upon wave modification and amplification is severe in the period range of 1-10sec.…”

Section: Discussionmentioning

confidence: 99%

“…The reduction process is quite satisfactory, except for 1.4km depth measurements, where large noises having a similar frequency to the S wave signal were predominant. The reason why noises were exclusively large at this depth, can be explained by the fact that cementing of the casing-pipe was not complete around 1.4km in depth (H. SUZUKI, oral communication, 1978;OHTA et al, 1980). 4.…”

Section: Data Reductionmentioning

confidence: 99%

“…This suggests that the Swave velocity of soil deposits at the present site is rather continuously varied with depth than stepwise. Also in previous works (OHTA et al, 1978(OHTA et al, , 1980, the continuous velocity was suggested by comparing the P-wave velocity with the sonic-velocity logging data. The revised model, therefore, can be considered as an approximation for the continuous velocity distribution.…”

Section: Data Reductionmentioning

confidence: 99%

“…Also in seismology, it is evident that the shallower earth structure is indispensable for the precise analysis of seismic source process by means of near-field long-period seismic waves. From these points of view, the authors carried out the direct measurement of S-wave velocity beneath the Tokyo metropolitan area (OHTA et al, 1977(OHTA et al, , 1978(OHTA et al, , 1980YAMAMIZU and GOTO, 1978;, where thick sediments with the S-wave velocity smaller than about 1.5km/sec are widely deposited down to the depth of 2-4km. In these measurements, three deep boreholes were temporarily used.…”

Section: Introductionmentioning

confidence: 99%

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Attenuation of shear waves in deep soil deposits as revealed by down-hole measurements in the 2,300 meter-borehole of the Shimohsa observatory, Japan.

et al. 1983

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Shear wave attenuation in deep soil deposits down to 2.3km in depth was directly and systematically measured at one of the deep-borehole observatories which were constructed for geophysical observations in the Tokyo metropolitan area.Introducing the newly designed SH-wave generator for an S-wave source, the down-hole measurements at 12 different depths were conducted down to 2.3km at intervals of 0.1-0.3km. Attenuation factors determined by the spectral ratio method were linearly inverted to QS-values under an assumption of frequency-independent QS.bottom of deep soil deposits, respectively, and larger than 150 in the substratum, for the frequency range of 3.5-20Hz.The QS for about 20 of the upper-most soil layer is faily consistent with known values which were estimated in shallower wells at various places.The substratum QS-value of 150 or over is not inconsistent with the crustal QS.The present measurement in such deep soil deposits is a new contribution to seismological and earthquake engineering studies.A significant effect of the attenuation factors upon the seismic waves is present by computing the amplification characteristics of deep soil deposits. At the present experimental site, the attenuation factor has a rather drastic effect upon the S wave in the period range shorter than 3sec.

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On the generation of P and S wave energy in crystalline rocks

Wright¹,

Johnson²

1983

International Journal of Rock Mechanics and Mining Sciences &am

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S-wave velocity measurement in deep soil deposit and bedrock by means of an elaborated down-hole method

Cited by 5 publications

References 0 publications

On the Generation of P and S Wave Energy in Crystalline Rocks*

On the Generation of P and S Wave Energy in Crystalline Rocks*

Attenuation of shear waves in deep soil deposits as revealed by down-hole measurements in the 2,300 meter-borehole of the Shimohsa observatory, Japan.

On the generation of P and S wave energy in crystalline rocks

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