Preliminary results from a study related to the subduction of the Juan De Fuca Plate beneath the North American Plate off the coast of Washington and British Columbia indicate that the potential mega-thrust earthquake could strike closer to the Seattle-Tacoma area than previously thought. I believe this project is the same one where I posted their press release about two years ago. According to the article, the average return period for these mega-thrust earthquakes is 400 to 500 years with a range between 300 and 800 and the estimated magnitude of around 9.0. The last mega-thrust earthquake along the Cascadia Subduction Zone was in January of 1700. Previously, scientists predicted the earthquake would be centered just off the coast, they now think it could be 30 miles or more inland, under the Olympic Peninsula to the west of the Seattle-Tacoma area. Source: Physorg.com via Geology.com.
A deadly magnitude 6.3 earthquake struck Christchurch, New Zealand on February 22, killing at least 147 and with around 200 still missing. Many buildings have been badly damaged or destroyed and residents also had to deal with large quanities of mud and water which was a result of the liquefaction. The same region was affected by a 7.1 magnitude quake in September of 2010. That earthquake was centered deeper and farther from the metropolitan area so there were fewer casualties and less damage. But many buildings that had recently been repaired, or were even still under repair were devastated once again. Some early reports were calling this earthquake an aftershock of the September earthquake, but maps I’ve seen (at right) show pretty clearly it was a different fault segment that ruptured during this earthquake. I have a collection of links below that might be of interest. My heart goes out to the people of New Zealand affected by this disaster.
Released: 4/14/2008 12:02:15 PM
California has more than a 99% chance of having a magnitude 6.7 or larger earthquake within the next 30 years, according scientists using a new model to determine the probability of big quakes.
The likelihood of a major quake of magnitude 7.5 or greater in the next 30 years is 46%-and such a quake is most likely to occur in the southern half of the state.
[Editor] At Left: Figure 1. The colors on this California map represent the UCERF probabilities of having a nearby earthquake rupture (within 3 or 4 miles) of magnitude 6.7 or larger in the next 30 years. As shown in the table, the chance of having such an event somewhere in California exceeds 99%. The 30-year probability of an even more powerful quake of magnitude 7.5 or larger is about 46%. [/Editor]