An evaluation of strong motion records and a new parameter A95

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Abstract
From the past studies of acceleration records, it is generally recognised that peak acceleration is not a suitable measure of the ground motion for design purposes. Usually, peak accelerations are difficult to predict. They occur in high frequency pulses containing very little energy and therefore are of little consequence. On the other hand acceleration has direct and useful application in engineering design.A new parameter A95 is introduced in this paper which is defined as that level of acceleration which contains up to 95 per cent of the Arias Intensity. From the study of 135 records, it is noticed that the variation of the fraction of Arias Intensity with acceleration level can be described by a very well defined relationship. It is also observed that A95 and Arias Intensity bear a stable relationship. Furthermore, the Arias Intensity at a site correlates more closely with the earthquake magnitude and the distance of the site from the source in attenuation relationships. From the available data, relationships are derived which show that there is a difference between the near‐field and the far‐field attenuation laws.The following relationships are obtained: equation image where Es = Arias Intensity, Ex = fraction of Arias Intensity above an acceleration level A, M = surface wave magnitude, R = nearest distance to the energy source or focal distance in km.

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