what was the magnitude of the northridge earthquake
1994 Northridge earthquake The 1994 Northridge earthquake occurred on January 17, at 4:30:55 a.m. PST and had its epicenter in Reseda, a neighborhood in the north-central San Fernando Valley region of Los Angeles, California. It had a duration of approximately 10–20 seconds. The blind thrust earthquake had a moment magnitude (Mw) of 6.7, which produced ground acceleration that was the highest ever instrumentally recorded in an urban area in North America,[5] measuring 1.8g (16.7 m/s2)[6] with strong ground motion felt as far away as Las Vegas, Nevada, about 220 miles (360 km) from the epicenter. The peak ground velocity at the Rinaldi Receiving Station was 183 cm/s[7] (4.09 mph or 6.59 km/h), the fastest peak ground velocity ever recorded. In addition, two 6.0 Mw aftershocks occurred, the first about one minute after the initial event and the second approximately 11 hours later, the strongest of several thousand aftershocks in all.[8] The death toll was 57, with more than 8,700 injured. In addition, property damage was estimated to be between $13 and $50 billion,[9] making it one of the costliest natural disasters in U.S. history.