Shake, rattle, and roll...to scale

Last week was spring break here in Madison, WI.  It’s been a while since I took part in the annual mass exodus, but I decided to take advantage of the time off, pack up, and get out of Dodge for a few days.  My destination was chilly, drizzly Seattle for an in-person crash course about the study of earthquakes and their associated dangers in the Puget Sound area.  I also went out to meet some of the people—both professional scientists and volunteer citizens—who are helping this effort along.

Spring Break 2011!  Downtown Seattle as seen from West Seattle across Elliott Bay.

The timing of my trip during the week after Japan’s subduction-related magnitude 9.0 Tohuku earthquake and the resulting tsunami, and not long after a shallow crustal temblor hit Christchurch, NZ, was purely coincidental.  It did, however, provide an engaging, albeit tragic, backdrop for discussing earthquake hazards in the area and individual motivations for contributing to the study of these hazards.  The susceptibility of the Puget Sound to both of these types of earthquakes, as well as to large deep earthquakes such as the 2001 Nisqually quake, and the parallels to these recent events is not lost on many in the region.

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.

Kaboom! An undersea volcano blows its top…

This spectacular video of an erupting undersea volcano recently came through the geoscience grapevine, and thought I would share it here.  Enjoy!

According to the anonymous voice accompanying the video, the volcano is Kavachi (9.02° S 157.95° E), near the Solomon Islands.  The eruptive history of Kavachi has been recorded since 1939 and numerous periods of volcanism have been documented in that time.  Although the date of this video is uncertain, the most recent known eruption occurred in early April 2007 following a magnitude 8.1 earthquake.  Kavachi has emerged above the ocean surface to form an island on nine occasions, only to subside again due to erosion.