The Whittier Narrows, California Earthquake of October 1, 1987—Note on Peak Accelerations during the 1 and 4 October Earthquakes

Abstract

Attenuation patterns of the recorded peak accelerations during two moderate earthquakes (M_L = 5.9 and 5.3) in Los Angeles, California are described. It is shown that the recording of earthquake motions by dense arrays of accelerographs can yield a detailed and deterministic picture of the physical processes which are involved in shaping the observed variations of strong ground motion. For the two earthquakes the observed changes of peak amplitudes with respect to the azimuth and distance are slowly and continuously changing functions showing strong dependence of amplitudes on the radiation patterns of the two earthquakes and on the effects of wave propagation through irregular three-dimensional geology of the Los Angeles basin.