The U.S. Geological Service reported a 6.9 magnitude earthquake off the coast of northern California last night. The quake, which hit at 10:18 p.m. PT, originally was classified on the Richter magnitude scale as a 6.1 but was later adjusted upwards by seismologists. A number of aftershocks occurred with at least one of them being significant at a 4.6 magnitude. The California earthquake’s epicenter was 48 miles off the coast of Ferndale, 50 miles distant from Eureka, and 247 miles away from Sacramento.
The Pacific Tsunami Warning Center reported that given all data available, the earthquake should not produce a destructive tsunami. The potential for an earthquake off the coast of California generating a tsunami is a big consideration not only for those in California but those in Hawaii as well. Because a tsunami is a series of seismic sea waves created by an underwater disturbance, such as the recent earthquake, it may cause significant amounts of destruction to coastal areas. Disturbances may be caused by such things as underwater earthquakes, volcanic eruptions, landslides, or even meteorites.
Tsunamis can produce waves up to 100 feet high and travel at speeds measured in the hundreds of miles per hour. After an underwater disturbance occurs, the tsunami travels outward from the epicenter. The wave builds in height as it reaches the shore. The height of the wave is dependent upon the size of the disturbance and the topography of the ocean floor and the coastline itself. The most destructive tsunamis to hit the United States have struck the coastlines of California, Hawaii, Alaska, Oregon, and Washington. Experts at the National Oceanic and Atmospheric Administration (NOAA) have the primary responsibility to provide warnings of impending tsunamis to the United States. This recent 6.9 magnitude earthquake off the coast of northern California has not required the NOAA or the Pacific Tsunami Warning Center to issue any cautionary statements.
While this quake has not generated a tsunami, it is the strongest earthquake off the coast of northern California in over 20 years. The last one was a 7.2 magnitude earthquake back in April, 1992. Both sheriff and fire officials report that in the most populated areas closest to the center of last night’s quake, they have had no significant damage or injuries. Current reports indicate that the rumble was felt for a much longer time than expected. In fact, Eureka police reported that the shaking continued for approximately 30 seconds.
Eureka, a city populated by approximately 27,000 residents, is no stranger to earthquakes. The city often feels tremors. The last, largest one in the area was in 2012 rating 5.6 on the Richter scale. That quake, like this one, did not cause injuries or severe damages. After the rumble last night, residents still had power. More than 3,000 people reported the quake on the USGS website.
This earthquake has a 90 percent expectation of producing aftershocks greater than magnitude 5.0 within the next seven days. Additionally, there is a chance that sometime in the next week northern California will experience quake either as large as, or larger, than last night’s 6.9 magnitude earthquake.
By Dee Mueller