We decided as a team that we have not provided an adequate geological and scientific purpose of our time here at sea. So, here is a little background knowledge which helps not only you, but us understand our time here on station. The Cascadia Initiative 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 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.
Now that we have that out of the way, it’s back to the saga of the lost TRM. By the time John and I woke up for our next watch, excitement, albeit negative excitement, was high. Last night while on site for Jason testing, a winch test of a Trawl Resistant Mount (essentially a hood that covers the OBS and protects it from fisherman nets) failed. The line snapped under the weight of the hood for reasons unknown and the hood was lost overboard. Thankfully we can put our faith in the capable robotic hands of Jason to save the day. A plan was implemented to deploy Jason down to the bottom of approximately 950 meters of water to search for our renegade TRM.
Needless to say, John and I were pumped that Jason was about to spring into action on our watch because that means we were headed to the control room! It took some time for preparations, and it took more time to finally get to the bottom, but once we were there, the Jason control van was squared away and on point. After passing by shrimp, octopus, a school of anchovies and fish, we found our wayward TRM. We put a fix on it, went back to the surface to load Jason up with some tools, and back down to put a hook on it. Of course all of this took time and our watch expired by the time the TRM was fully retrieved, but the jubilance was had when the cameras eyes were feasting on the upturned TRM, and we were there with our fork and knife.
In all fairness, Hanna and Astrika’s watch when we were relieved must have been really interesting as well. Being able to see the human-like dexterity of Jason operating nearly 1000 meters beneath the surface was surely exciting. The ability to attach a clamp and line to the side of the TRM with robotic hands and arms is pretty amazing. Later on their watch and into Natsumi and Caitlin’s watch, Jason and Madea were retrieved and we continued about our business.
Of note, we were close enough to the shoreline for a phone call today. While out on deck feeding my addiction to connection, I spotted two orcas off of the port beam, marking the first time I’ve ever seen them in the wild. It was pretty amazing.