Source spectra and site-response estimates using the Coda of Lg waves in western Europe

S. Chevrot; Y. Cansi

doi:10.1029/96gl01480

Spectral Analysis of K-NET and KiK-net Data in Japan, Part II: On Attenuation Characteristics, Source Spectra, and Site Response of Borehole and Surface Stations

Bulletin of the Seismological Society of America ◽

10.1785/0120100135 ◽

2011 ◽

Vol 101 (2) ◽

pp. 667-687 ◽

Cited By ~ 66

Author(s):

A. Oth ◽

D. Bindi ◽

S. Parolai ◽

D. Di Giacomo

Keyword(s):

Spectral Analysis ◽

Site Response ◽

Source Spectra ◽

Attenuation Characteristics

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Site response and source spectra of S waves in the Zagros region, Iran

Journal of Seismology ◽

10.1007/s10950-012-9344-1 ◽

2012 ◽

Vol 17 (2) ◽

pp. 645-666 ◽

Cited By ~ 7

Author(s):

H. Zafarani ◽

B. Hassani

Keyword(s):

Site Response ◽

S Waves ◽

Source Spectra ◽

Zagros Region

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Comparison of strong-motion spectra with teleseismic spectra for three magnitude 8 subduction-zone earthquakes

Bulletin of the Seismological Society of America ◽

10.1785/bssa0800040913 ◽

1990 ◽

Vol 80 (4) ◽

pp. 913-934

Author(s):

Heidi Houston ◽

Hiroo Kanamori

Keyword(s):

Half Space ◽

Site Response ◽

Strong Motion ◽

Body Waves ◽

Reference Spectrum ◽

Empirical Relations ◽

Finite Fault ◽

Simple Physical Model ◽

Source Spectra ◽

The Difference

Abstract We studied strong-motion spectra observed for three Mw 7.8 to 8.0 earthquakes (the 1985 Michoacán, Mexico; 1985 Valparaíso, Chile; and 1983 Akita-Oki, Japan earthquakes). We determined the decay of spectral amplitude with distance from the station, considering different measures of distance from a finite fault. We compared strong-motion spectra (Fourier acceleration spectra) observed for these three earthquakes with those estimated from the source spectrum determined from teleseismic P waves. We scaled the teleseismic source spectra to produce reference strong-motion spectra at periods from 1 to 10 sec using a simple physical model of far-field S body waves from a point source recorded at the surface of a homogeneous half-space. For all three earthquakes the reference spectral amplitudes at periods of 1 to 5 sec are about half the observed ones at distances of about 50 km. The difference increases as the distance increases. At distances of 200 to 300 km, the reference spectrum is about 1/10 of the observed one. The difference between the reference and the observed spectrum is attributed to the contribution of phases other than direct S waves and to site response. We applied corrections for the finiteness (spatial extent) of the source using a simple model of rupture propagation on a dipping two-dimensional fault. Including the source finiteness did not improve the estimate substantially at periods from 1 to 20 sec, but it modeled significant changes in the signal duration as a function of azimuth for the 1985 Michoacán earthquake. Our results can be used to establish empirical relations between the observed spectra and the half-space responses, depending on the distance and the site condition. If such empirical relations can be established, source spectra determined from teleseismic records may be used to estimate strong motions.

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Statistical spectral model of earthquakes in the eastern Tohoku district, Japan, based on the surface and borehole records observed in Sendai

Bulletin of the Seismological Society of America ◽

10.1785/bssa0870020446 ◽

1997 ◽

Vol 87 (2) ◽

pp. 446-462

Author(s):

Toshimi Satoh ◽

Hiroshi Kawase ◽

Toshiaki Sato

Keyword(s):

Stress Drop ◽

Site Response ◽

Standard Penetration Test ◽

Spectral Model ◽

Corner Frequency ◽

Quantitative Prediction ◽

S Wave ◽

Frequency Dependent ◽

Initial Values ◽

Source Spectra

Abstract Strong motions of 18 earthquakes (3.4 ≦ MJ ≦ 7.1, MJ: JMA magnitude) in the eastern Tohoku district, Japan, have been observed at 12 borehole sites within a 20- × 20-km region in Sendai. In our previous study, we defined a Pliocene layer, whose S-wave velocity VS is greater than 500 m/sec and whose N value of the standard penetration test is greater than 50, as engineering bedrock in Sendai and calculated 304 engineering bedrock waves (hypocentral distance X = 15 to 300 km) by removing the site response between the engineering bedrock and the surface. As the second stage of our study toward a quantitative prediction of strong ground motions of horizontal components, we propose here a statistical spectral model of the engineering bedrock waves by introducing the site response between the pre-Tertiary bedrock (VS ≈ 3000 m/sec) and the engineering bedrock (VS ≈ 500 to 700 m/sec) and a frequency-dependent Q into Boore's spectral model. We separate the site response between the pre-Tertiary bedrock and the engineering bedrock, an attenuation function, and source spectra from the engineering bedrock spectra by assuming an ω−2 model with the seismic moment M0 from the Harvard CMT solution estimated for earthquakes of MJ ≧ 5.3. Initial values of corner frequency f0 are determined based on a previous empirical M0 − f0 relationship in this district. Using six moderate-sized earthquakes (5.3 ≦ MJ ≦ 6.0), we first estimate frequency-dependent Q to be Q = 110f0.69 (f: frequency) by minimizing the standard deviation of the site response, which is defined as the ratio of observed engineering bedrock spectra with respect to the estimated attenuation and the assumed source spectra. The averaged site response is simultaneously estimated to be 1 at 0.1 Hz, 5 at 1 Hz, and 3 at 20 Hz. We then invert f0 and cutoff frequencies fmax for all 18 earthquakes and M0 for seven small-sized earthquakes of MJ < 5.3 by minimizing the difference between the model and observed spectra. The average Brune stress drop obtained from an M0 − f0 relationship estimated from 17 earthquakes except for the smallest earthquake with M0 less than 1021 dyne·cm is 200 bars. The estimated M0 − f0 relationship is identical to the one used to calculate initial values of f0 so that we do not need to perform the inversion iteratively. The obtained stress drop for subduction zone earthquakes in the eastern Tohoku district is consistent with other previous studies. The dependence of the inverted fmax on M0 is not significant, and the logarithmic average of fmax is found to be 13.5 Hz. By using these controlling parameters and the M0 − f0 relationship obtained from a regression analysis, acceleration spectra on the engineering bedrock in Sendai can be predicted statistically from X and M0 or MJ by considering standard deviations of the site response, f0, and fmax.

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