Ocean Bottom Seismology in the Pacific Northwest Days 1-3.


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North America » United States » Washington
July 13th 2012
Published: July 13th 2012EDIT THIS ENTRY

Hello from the Pacific Northwest! Finally found myself a little downtime to write about what has been going on here. I arrived into Seattle-Tacoma airport around 9:45 on Sunday night and took a cab up to the University of Washington (U-district) where I met the boat (R/V Thomas G. Thompson). I was pretty beat from a week+ of vacation (spoken: partying), so I didn’t have a lot of energy to explore, but I was able to find my stateroom (yeeeaaaa I had a stateroom, woot! woot! photo 001(2)), the crew’s mess and the main lab where I will be spending most of my time (photo 037). My roommate John was nice enough to make my rack up with bedding so I didn’t wake him up when I got here, so I just hit it and tried to adjust to my new home and time zone.
The next day we had a meeting with Dr. Maya Tolstoy, our professor and Chief Scientist for this particular Ocean Bottom Seismology (OBS herein) expedition which is part of a larger, 4-year project called the Cascadia Initiative (CI). The CI is “an onshore/offshore seismic and geodetic experiment that takes advantage of an amphibious array to study questions ranging from megathrust earthquakes to volcanic structure to formation, deformation, and hydration of the Juan de Fuca and Gorda plates.” (Tolstoy) Generally speaking, our purpose here is to collect 24 OBS units that were deployed last year and deploy 6 which will be collected next year. From these units we can collect raw data which will be analyzed and interpreted by the scientists and students working on the project. What they are looking at is movement of the Juan de Fuca plate. Of specific interest is the accretionary prism (which is sediment that has been scraped off of the subducting or downgoing plate by the overriding plate, think snowplow on the street with snow gathering in the shovel portion) and a new phenomenon known as Episodic Tremor and Slip (ETS herein), slow slip on the downgoing plate beneath the locked zone, that has been observed to be the predecessor of major earthquake events. The goal is to gather data from these tremors along the fault and in the long term use it for earthquake forecasting. Of course there is much to be learned about this seismic activity before that comes to fruition including where it is exactly happening along the faults and its direct relationship to events. Understanding the The general geology behind the fault zone is the colder, denser oceanic plate (Juan de Fuca) is subducting beneath the warmer, more buoyant continental plate (North America). This collision results in the scraping mentioned earlier, but earthquakes occur when the tension in the locked zone reaches a certain level and eventually flicks back to a more stable state releasing large waves of energy through the earth’s interior and exterior.
Armed with a little bit of background knowledge and our marching orders for the underway at 0830 the following morning, the grad and undergraduate students made their way into Seattle for a little sightseeing and fun! On our agenda was the famous public market which has everything from fruit, flowers and fresh groceries to off-the-dock fish and crustaceans which are very professionally thrown at err to customers and co-workers. From there we wandered around downtown Seattle, unsuccessfully attempting to locate a spot high enough to get a glimpse of Mt. Rainier. The only way to solidify that spot was to get up into the space needle, so before there we picked up a smoothie and made one last stop at the original Starbucks where there was a fantastic bluegrass band, “The Tallboys” playing out in front (photo 1393). I snagged one of their cd’s and it was off to the needle (photo 1401)! Even though the weather was overcast and foggy (shocker), the views from the top were still pretty spectacular (photo 1412)! After the needle, we headed back to get changed and go out for a widely recommended Thai meal in U-district. It lived up to the hype, excellent food. Knowing that we were going to be sans beer for the next couple weeks, I stopped and picked up a 12-pack for the group that we enjoyed at the Oceanography building overlooking the canal. When the last drop was drank, it was time to hit the rack and prepare to get haze grey and underway! Night y’all!



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