How Accurate Can Strong Ground Motion Attenuation Relations Be?

abstract Two proposals are presented on the estimation of maximum accelerations of strong ground motion near the causative fault. First, the crucial selection of the form fitted to observed accelerations as a function of distance from the source is discussed. In particular, evidence is given that the attenuation form adopted by Joyner et al. (1981) constrains the attenuation parameters so that inferences on near-fault motion and magnitude dependence are questionable. An alternative attenuation form is proposed which decouples far-field variations from near-field variations. Nonlinear least-squares regression to the same data set confirms the flattening of attenuation curves near to the source (<10 km) in the magnitude range 5.0 < M < 7.0 and shows no indication (from the small amount of data available) of any additional increase in acceleration for M > 7 earthquakes. For 6.0 ≦ M ≦ 7.7, the regression yields y = 1.6 { ( x + 8.5 ) 2 + 1 } − 0.19 exp { − 0.026 ( x + 8.5 ) } where y is the peak horizontal acceleration in g, and x (km) is the closest distance to the surface projection of the rupture. Second, a robust and easily computed parameter is defined for significant peak acceleration that meets many engineering requirements. This “effective” peak acceleration is obtained by developing histograms for the number of peaks and troughs on the observed record and by choosing the acceleration value at about the 90 percentile level. This truncation excludes scattered outliers of high-amplitude peaks not representative of the general distribution of the ground motion amplitudes. Corresponding values for “effective peak acceleration” are tabulated for part of the basic data set, and it is demonstrated that the scatter about the attenuation regression line is reduced using the proposed parameter.

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Estimation of attenuation relations for strong-motion data allowing for individual earthquake magnitude uncertainties

Bulletin of the Seismological Society of America ◽

10.1785/bssa0870061674 ◽

1997 ◽

Vol 87 (6) ◽

pp. 1674-1678

Author(s):

David A. Rhoades

Keyword(s):

Ground Motion ◽

Regression Models ◽

Strong Ground Motion ◽

Strong Motion ◽

Error Variance ◽

Attenuation Relations ◽

Motion Data ◽

Different Levels ◽

Magnitude Determination ◽

Strong Ground

Abstract Standard errors of earthquake magnitudes are routinely calculated and vary appreciably between earthquakes. However, the uncertainties of magnitude determination are usually ignored in regression models of strong ground motion as a function of magnitude and distance from the earthquake source. This practice has the potential to bias estimates of strong ground motion. A method is given for taking account of the uncertainty of each magnitude determination in fitting such models. It extends previous methods in which the error variance is partitioned into between-earthquake and within-earthquake components. It allows for further decomposition of the between-earthquake component into a part attributable to magnitude uncertainties and a part attributable to other causes. The method has been applied to the well-known attenuation data of Joyner and Boore (1981). The Mw determinations in this dataset fall into two subsets with distinctly different levels of precision, namely, those determined directly and those inferred from values of ML. It is shown that most of the between-earthquake component of variance can be attributed to the relatively low precision of the magnitudes in the latter subset.

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Attenuation Relations of Strong Ground Motion in Japan Using Site Classification Based on Predominant Period

Bulletin of the Seismological Society of America ◽

10.1785/0120050122 ◽

2006 ◽

Vol 96 (3) ◽

pp. 898-913 ◽

Cited By ~ 326

Author(s):

J. X. Zhao

Keyword(s):

Ground Motion ◽

Strong Ground Motion ◽

Site Classification ◽

Attenuation Relations ◽

Predominant Period ◽

Strong Ground

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