Northridge 20 Years After

Urban earthquakes such as the 1994 M 6.7 Northridge earthquake provide unique moments of clarity for those of us working on earthquake hazards. I recall being jolted awake at 4:31 a.m., 17 January 1994, in my Pasadena home. As I hurried to my U.S. Geological Survey (USGS) office on the Caltech campus, I remember wondering what the day would bring. Was the epicentral region sparsely populated, or had we just taken a direct hit to urbanized Los Angeles (LA)? We now know that, although damaging shaking extended into the LA basin, it was the San Fernando Valley that experienced truly violent shaking; five strong-motion accelerometers recorded peak ground velocities (PGV) of more than 1 m=s. Although the attack was over in 15 seconds, it left behind about $20 billion in damage and millions of terrified Angelenos, especially those living in the San Fernando Valley