Seattle area’s evolving earthquake threat

Several recent studies from the world of geology have relevance in this damp corner of the country.  They point to the possibility that “the big one” might be bigger than we thought.

Lesson from Indonesia. They’ve had 5 major earthquakes in the past 5 years, including the famous tsunami of 2004.  A more recent quake and tsunami off the coast of Sumatra was eerily like the one that’s predicted to hit the coast of Washington and Oregon some day.  Major lessons?  As I reported for KPLU, it showed that these deep quakes could be more powerful than previously thought.   There was no tsunami this time, but the public knew enough to head for high ground anyway, just in case.

Slow quakes and Mega-quakes. You may have heard of “slow earthquakes” (also known as “deep tremors”). They happen pretty regularly in the land of Cascadia, as the power of a big earthquake is released slowly over a period of weeks.  We don’t feel anything, because the energy is spread out over time.  The leading theory is these release energy in one area as two plates on Earth’s crust slide past each other–but add to the pent-up energy at a deeper spot.  Now, scientists (led by Ken Creager at the U. of Washington) find a second type of unfelt tremor may be adding even more tension to the fault zone that runs beneath the Interstate-5 zone.  If so, that means “the big one,” whenever it happens, could be bigger than previously thought.  Geologists and engineers have to go back and re-do some calculations to see if we need to change our building codes.

Could this seismograph fit in your basement?

Volunteer to be a basement seismologist. The U.S. Geological Survey and U.W. are looking for modest size homes throughout the Seattle area, to create a network of sensors.  A similar project is underway in the San Francisco area.  They’ll get data on how different soils and different types of structures respond to shaking.  They need a spot on a concrete floor about 2 ft. x 2 ft. with electrical power and potential internet connection.  To sign up, check out the NetQuakes program.

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