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OSMS 95-14

"Strong Ground Motion Data From the 1994 Northridge, California, Earthquake"

by Robert Darragh, Anthony Shakal and Moh Huang

Darragh, Robert, Anthony Shakal and Moh Huang (1995). Strong Ground Motion Data From the 1994 Northridge, California, Earthquake. The Northridge, California, Earthquake of 17 January 1994: California Department of Conservation, Division of Mines and Geology Special Publication 116, p. 55-63.

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Introduction

The 6.7 M (moment magnitude) earthquake that occurred near Northridge, California on January 17, 1994 produced an important set of strong-motion recordings. Strong-motion records were obtained from over 700 stations. These stations include more than 250 ground-response stations, 400 buildings, and 50 other structures.

Some of the highest acceleration ever recorded at ground-response and structural sites occurred in the Northridge earthquake. These accelerations are greater than most existing attenuation models would have predicted and are also higher than the 1971 San Fernando earthquake. The thrust mechanism of this event as well as its location under a metropolitan area may have contributed to the number of high acceleration recordings. Although the accelerations are high, the correspondence between measured acceleration and damage requires further study, since some sites with high acceleration experienced only moderate damage. Some vertical accelerations were larger than the horizontal, but in general this event fits the pattern observed in previous earthquakes. Strong-motion records processed to date show significant differences in acceleration and velocity waveforms and amplitudes across the San Fernando Valley.