Analysis of a worldwide strong motion data sample to develop an improved correlation between peak acceleration, seismic intensity, and other physical parameters

Abstract

Results of a continuing investigation of the correlations between seismic intensity and ground motion are reported. An updated strong motion sample consisting of data measured from nearly 1600 accelerograms forms the basis for these investigations. Statistical analyses of these data have yielded correlation equations. They indicate a dependence of the acceleration/intensity correlation on magnitude, epicentral distance and possibly the geographical region or tectonic province in which the earthquakes are occurring. The difficult problem of identifying and explaining regional anomalies in the acceleration/intensity correlation is addressed and evidence is presented which suggests that the Southern European anomaly may be related to the fact that the spectral composition of the near-field ground motions measured in Southern Europe are unusual and that this may reflect regional differences in the dynamic characteristics of the earthquake sources. The influence of local site geology on the acceleration/intensity correlation has also been examined in more detail, including the measured effects at a specific station in New Guinea at which an unusually large peak acceleration amplification has been identified and documented. It has been concluded that the local amplification of the peak acceleration is generally controlled by the overburden thickness at the site, due to the fact thatmore » the peak acceleration pulse is attenuated as it propagates through the imperfectly elastic layer of alluvium. A new correlation equation in which the magnitude variable is replaced by epicentral intensity is derived for purposes of applications to the assessment of historical earthquakes for which no instrumentally determined magnitudes are available. Preliminary results suggest that intensity may be much more strongly correlated with response spectral amplitudes in narrow period bands than with any single peak ground motion parameter.« less