Nisqually...10 Years On

Headline from the Seattle Post-Intelligencer, March 1, 2001.

Earthquake occurrences in the past seven days.
(Screen grab from www.usgs.gov)

A quick glance at the USGS' running tally of recent earthquakes in the U.S. (right) reminds us of the country's most tectonically active areas .  It's pretty clear: California and Alaska, followed by several other geographic pockets of notable activity.  For residents of one of those pockets--Seattle and the greater Puget Sound area--the February 28 dateline on the map at right carries special significance.

Today is the 10th anniversary of the magnitude 6.8 Nisqually earthquake, which struck the area at 10:54 a.m. local time on Wednesday, February 28, 2001.  Although it ranks as only the 82nd largest earthquake by magnitude (by my count) in the U.S., it is the third largest on record and the most recent significant quake in Washington state.

The quake originated at a depth of 52 km in the subsurface Juan de Fuca plate, which is subducting under the North American plate in the Cascadia subduction zone.  The epicenter (47.15N 122.72W) was located toward the southern end of Puget Sound, 17.6 km northeast of Olympia, WA and 57.5 km south southwest of Seattle.

Road Trip Photo Appendix

Thought I'd slap up a few of my shots that didn't make the initial road trip post...some science(ish), some just for fun.

Keeping Portland Weird: OMSI, i.e., Oregon Museum of Science and Industry (0.000000002 astronomical units ≈ 300 m if I got the conversion right)

The Joy of Road Tripping…with Geologists

Anyone who has ever willingly embarked on a road trip is no doubt aware that the enjoyment is more in the journey than in reaching your destination.  Or however the adage goes.  For history buffs, the joy might come from touring Civil War battlefields or traversing Route 66 in search of Americana.  For foodies, maybe its stopping off at a roadside diner for a taste of regional cuisine or seeking out the freshest farm-raised ingredients that does the trick. 

For geologists, professional and amateur alike, it’s simple.  It’s the rock below our feet and the rock towering over our heads.  It’s the physical and chemical processes that gave these rocks their distinct textures and flavors, and the tremendous forces that shape(d) them.  The biotic veneer that selectively coats the crust is fascinating and often beautiful in its own right, but for a geologist, it’s all about what’s underneath that counts.

My apologies for waxing philosophic.  I’ve got all this on the brain after returning from a long weekend of road tripping through the Cascades with two close friends—one a structural geologist and the other a seismologist.  What better way to see the mountains, right?  It’s like having a backstage pass: you get the insider’s scoop, far more interesting than the average self-guided tour.  Okay, so my friends aren’t the world’s foremost experts on the Cascades.  Nor are they park rangers who could sneak us up close and personal to the steaming vents of Mt. St. Helens.  Nonetheless, they are very bright, and they know a whole lot more than I do about these things (I was, after all, only a biogeochemist, as they jokingly remind me on occasion).