The National Weather Service Eureka Ca issued a special statement at 7.00 pm pst Saturday on Jan 9, 2010 saying that Eureka California and nearby cities Ferndale, Humboldt, Sacramento and Bayview experienced an earthquake measured at 6.5 magnitude, which struck the area at 4:27.

Residents across Northwest California had felt that a major quake was coming as this region had been shaking for quite some time.

According to the statement, no tsunami was generated by the Ferndale earthquake or Eureka earthquake expected along the west coast.  Aftershocks were felt in Eureka Ca and Ferndale Ca and other areas and are expected over the next few days.

Sheriff’s Department cpl Brenda Godsey was cited by the sfgate.com as saying that the earthquake struck about 27 miles southwest of Eureka Ca resulting in loss of electricity and phone service across the Humboldt County.

No personal injuries have been reported thus far in the Eureka earthquake or Ferndale earthquake as some called.

By Jimmy Downs

Earthquake Details

Cited from http://earthquake.usgs.gov/earthquakes/eqinthenews/2010/nc71338066/

Aftershock warning:

PROBABILITY REPORT 

Published on January 10, 2010 @ 01:13:57 GMT

Northern California Seismic Network (NCSN) operated by UC Berkeley and USGS 

Version 0: This report supersedes any earlier probability reports about this event. 

MAINSHOCK 

STRONG AFTERSHOCKS (Magnitude 5 and larger) - 

At this time (immediately after the mainshock) the probability of a strong and possibly damaging aftershock IN THE NEXT 7 DAYS is approximately 78 PERCENT 

EARTHQUAKES LARGER THAN THE MAINSHOCK - 

Most likely, the recent mainshock will be the largest in the sequence. However, there is a small chance (APPROXIMATELY 5 TO 10 PERCENT) of an earthquake equal to or larger than this mainshock in the next 7 days.

WEAK AFTERSHOCKS (Magnitude 3 to 5) -

In addition, approximately 70 to 20 SMALL AFTERSHOCKS are expected in the same 7-DAY PERIOD and may be felt locally. 

This probability report is based on the statistics of aftershocks typical for California. This is not an exact prediction, but only a rough guide to expected aftershock activity. This probability report may be revised as more information becomes available.

Background Information About Aftershocks 

Like most earthquakes, the recent earthquake is expected to be followed by numerous aftershocks. Aftershocks are additional earthquakes that occur after the mainshock and in the same geographic area. Usually, aftershocks are smaller than the mainshock, but occasionally an aftershock may be strong enough to be felt widely throughout the area and may cause additional damage, particularly to structures already weakened in the mainshock. As a rule of thumb, aftershocks of magnitude 5 and larger are considered potentially damaging. 

Aftershocks are most common immediately after the mainshock; their average number per day decreases rapidly as time passes. Aftershocks are most likely to be felt in the first few days after the mainshock, but may be felt weeks, months, or even years afterwards. In general, the larger the mainshock, the longer its aftershocks will be felt. 

Aftershocks tend to occur near the mainshock, but the exact geographic pattern of the aftershocks varies from earthquake to earthquake and is not predictable. The larger the mainshock, the larger the area of aftershocks. While there is no "hard" cutoff distance beyond which an earthquake is totally incapable of triggering an aftershock, the vast majority of aftershocks are located close to the mainshock. As a rule of thumb, a magnitude 6 mainshock may have aftershocks up to 10 to 20 miles away, while a magnitude 7 mainshock may have aftershocks as far as 30 to 50 miles away.