SOURCE EFFECTS ON STRONG MOTION RECORDS

Source effects on strong motion records are demonstrated using one of the best instrumented earthquakes to date. A large number of near-source, strong-motion records for the ۱۹۸۷ Whittier Narrows, California, earthquake are inverted to obtain the history of slip. The pattern of ۱۷ stations that form good ۳۶۰° azimuthal coverage of the source is expected to give good resolution. We use a modified version of the inversion method developed by Hartzell and Heaton [۹]. The results show a complex rupture process within a small source volume, with at least four separate concentrations of slip. 'The waveforms of data records and synthetics are fit well in both shape and amplitude. We find that the ground motions can be roughly explained by considering only source effects coupled with the same averaged propagation path effects to each strong motion station.