The Rinaldi Strong Motion Accelerogram of the Northridge,California Earthquake of 17 January 1994

Abstract

The Rinaldi record of the 1994 Northridge earthquake is one of the most important strong motion records in earthquake engineering (largest recorded horizontal peak ground velocity in the western United States, ∼170 cm/s). Digitization of this record was not straightforward because of numerous stalls and malfunction of the half-second pulse relays. It was digitized and processed for the Los Angeles Department of Water and Power soon after the earthquake, and was recently redigitized and reprocessed. This paper presents the results of the recent digitization and processing and a comparison of the two digital versions of the record. The “new” version differs from the “old” version in the number of stalls corrected for (17 versus one stall), total length of digitized traces (∼20 s versus ∼15 s), and amplitudes of some high frequency acceleration peaks (in the “old” version, some high frequency peaks have been underestimated). The peak amplitudes of corrected acceleration, velocity and displacement, and the linear response spectrum amplitudes are not significantly different. However, the two digital interpretations have different time scales, because of the difference in the number of stalls accounted for.