abstract

An analysis of acceleration/intensity correlations has been carried out using a new, worldwide data sample compiled for this study from data measured from nearly 1500 strong-motion accelerograms. This new data sample has been extensively analyzed using a variety of statistical models. It has been found that the correlation equation relating peak horizontal ground acceleration (aH) to Modified Mercalli intensity (IMM) which best describes the trends in the subset of this new sample consisting of the nearly 900 observations for which aH ≧ 10 cm/sec2 is

 
logaH=0.25IMM+0.25

for aH given in cm/sec2. Analyses of the dependence of this correlation on other variables such as local earthquake magnitude (M), epicentral distance (R) and the geographical region in which the earthquakes are occuring suggest that over the range of these variables encompassed by the available data, the correlation equation which best fits the data is

 
logaH=0.14IMM+0.24M0.68logR+βk

where R is given in kilometers and

 
βWesternUnitedStates=0.60βJapan=0.69βSouthernEurope=0.88.

Thus, the Southern European data indicate peak horizontal accelerations at fixed values of intensity, magnitude and epicentral distance which are about a factor of two higher than the corresponding values for the Western United States and Japan. Sufficient data are not yet available to determine whether this difference is due to a consistent measurement bias associated with the assignment of intensities in Southern Europe or to variations in the regional tectonic environment in which the earthquakes are occurring.

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