Compilation of strong-motion records from the August 6, 1979 Coyote Lake earthquake

Porcella, R.L.; Matthiesen, R.B.; McJunkin, R.D.; Ragsdale, J.T.

doi:10.3133/ofr79385

Cited by 12 publications

(4 citation statements)

References 2 publications

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“…Volume I of that series was used for acceleration instead of Volume II because the procedures used in producing Volume II tended to bias the peak acceleration toward lower values. For more recent earthquakes, sources of strong-motion data include Porter (1978), PorceUa (1979), Porcella et al (1979), Brady et al (1980), and Boore and Porcella (1981). In addition, unpublished data were made available by the California Division of Mines and Geology, by J. N. Brune for the stations of the cooperative program of the University of California at San Diego and the Universidad Nacional Autonoma de Mexico, and by Kinemetrics Inc. for the Shell Oil Company station at Munday Creek, Alaska.…”

Section: Datamentioning

confidence: 99%

Peak horizontal acceleration and velocity from strong motion records including records from the 1979 Imperial Valley, California, earthquake

Joyner¹,

Porcella²

1981

Open-File Report

226

332

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We have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relations for peak horizontal acceleration and velocity. This new analysis uses a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. An innovation in technique is introduced that decouples the determination of the distance dependence of the data from the magnitude dependence. The resulting equations are log A =-1.02 + 0.249M-log r-0.00255r + 0.26P r_-(d2-1-7.32) 1/2 5.0_

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Section: Datamentioning

confidence: 99%

Peak horizontal acceleration and velocity from strong motion records including records from the 1979 Imperial Valley, California, earthquake

Joyner¹,

Porcella²

1981

Open-File Report

226

332

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“…At station 2 values of 0.26 g and 32 cm/sec were recorded. At station 1 peak vertical acceleration was 0.08 g and peak vertical velocity 2.6 cm/sec versus 0.18 g and 6.6 cm/sec at station 2 (Porcella £t &]_. , 1979;Brady et_ ^1_., 1980). These records provide an especially favorable opportunity to study the effect'of sediments on earthquake ground motion at moderate amplitude levels.…”

Section: Introductionmentioning

confidence: 92%

The effect of Quaternary alluvium on strong ground motion in the Coyote Lake, California, earthquake of 1979

1981

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The effect of alluvium on strong ground motion can be seen by comparing two strong-motion records of the Coyote Lake, California, earthquake of August 6, 1979 (M. = 5.9). One record at a site on Franciscan bedrock had a peak horizontal acceleration of 0.13 g and a peak horizontal velocity of 10 cm/sec. The other, at a site 2 km distant on 180 m of Quaternary alluvium overlying Franciscan, had values of 0.26 g and 32 cm/sec, amplifications by factors of 2 and 3. Horizontal motions computed at the alluvial site for a linear plane-layered model based on measured P and S velocities show reasonably good agreement in shape with the observed motions but the observed peak amplitudes are greater by a factor of about 1.25 in acceleration and 1.8 in velocity. About 15 percent of the discrepancy in acceleration and 20 percent in velocity can be attributed to the difference in source distance; the remainder may represent focusing by refraction at a bedrock surface concave upward. There is no clear evidence of nonlinear soil response. Fourier spectral ratios between motions observed on bedrock and alluvium show good agreement with ratios predicted from the linear model. In particular, the observed frequency of the fundamental peak in the amplification spectrum agrees with the computed value, indicating that no significant nonlinearity occurs in the secant shear modulus. Computations show that nonlinear models are compatible with the data if values of the coefficient of dynamic shear strength in terms of vertical effective stress are in the range of 0.5 to 1.0 or greater. The data illustrate that site amplification may be less a matter of resonance involving reinforcing multiple reflections, and more the simple effect of the low near-surface velocity. Application of traditional seismological theory leads to the conclusion that the site amplification for peak horizontal velocity is approximately proportional to the reciprocal of the square root of the product of density and shear-wave velocity.

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“…The main shock of the 6 August 1979 Coyote Lake earthquake (ML = 5.9) triggered the system and resulted in the recording of approximately 27 sec of acceleration on each of the 12 channels. The peak recorded ground acceleration Porcella et al, 1979).…”

Section: Strong-motion Instrumentationmentioning

confidence: 99%

“…With the availability of a significant number of near-source strong ground motion records and also world-wide teleseismic data, the Coyote Lake earthquake has been well researched (Uhrhammer, 1980;Joyner et al, 1981;Liu and Heimberger, 1983). Compilations of strong-motion records recovered from the earthquake are given by Porcella et al (1979), and processed data from the San Juan Bautista bridge and the station in the town of San Juan Bautista are given by Porter et al (1983). Liu and Heimberger (1983) report that the earthquake was nearly a pure strike-slip mechanism with strike (N24 oW) parallel to the Calaveras fault.…”

Section: Strong-motion Instrumentationmentioning

confidence: 99%

Spatial variation of ground motion determined from accelerograms recorded on a highway bridge

Wilson

Jennings

1985

Bulletin of the Seismological Society of America

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A set of time-synchronized strong-motion accelerograms, obtained on the San Juan Bautista 156/101 Separation Bridge in California during the 6 August 1979 Coyote Lake earthquake (ML = 5.9), are used to study the spatial variation of ground motion at the bridge site, including traveling wave effects and the influence of multiple-support excitation. Analysis of the ground motion recorded at the base of two of the bridge supports (32.6 m apart) revealed the presence of a differential support excitation having a period of ≈ 3 sec, much longer than any structural periods of the bridge. This signal also appeared as a noticeable long-period component in the superstructure displacements. Analysis of the vertical and radial components of the 3-sec ground motion indicated that ground displacements were retrograde for the duration of strong shaking, with several cycles exhibiting elliptical particle motions. These findings suggest that long-period differential support motions were induced by phase delays in a Rayleigh wave traveling across the bridge site. Further support to this premise is given by the location of the bridge site near a maxima of the Rayleigh wave radiation pattern for the Coyote Lake earthquake (based on published focal mechanism data). Traveling wave effects were also detected for compressional body waves by a correlation analysis which indicated a time delay of ≈ 7 msec between P-wave arrivals at two of the bridge supports.

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Compilation of strong-motion records from the August 6, 1979 Coyote Lake earthquake

Cited by 12 publications

References 2 publications

Peak horizontal acceleration and velocity from strong motion records including records from the 1979 Imperial Valley, California, earthquake

Peak horizontal acceleration and velocity from strong motion records including records from the 1979 Imperial Valley, California, earthquake

The effect of Quaternary alluvium on strong ground motion in the Coyote Lake, California, earthquake of 1979

Spatial variation of ground motion determined from accelerograms recorded on a highway bridge

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