Day 3: Oh buoy, here we go!

We are officially underway! After departing Seward dock at 8:30am and having donned our full-body immersion suits as part of a safety drill (fortunately we were allowed to take them off afterwards), we’re now heading towards the first seismometer deployment site, LT03, which lies in the Shelikof Strait just north of Kodiak Island.

Map of our deployment sites. Each orange triangle is a location where we will drop an ocean bottom seismometer (OBS). The blue dot shows our current location in the Shelikof Strait, between Kodiak Island and the mainland.

Now that the cruise has begun, lets introduce the ship in a little more detail.

Its hardly luxurious, but we’re fortunate enough to be on board one of the most modern and well-equipped scientific research ships in the world. RV Sikuliaq was built in 2014 and was purposely designed for science missions. At 261 ft it’s a decent sized ship – there’s a science lab, lounge, dining room, kitchen, gym … the list goes on. Infact there’s even a sauna (which apparently can double as a ‘hypothermia recovery room’, but lets hope we won’t be using it for that purpose). As far as cabins are concerned, we’re treated to the height of oceanographic luxury – practical, comfortable rooms. You could event claim they’re en-suite (kind of, since the facilities are shared with the room next door). The Sikuliaq is capable of breaking ice of up to 2.5ft thick, which is fantastic on polar missions but means that the ship’s hull is much more rounded than those of non-icebreakers. This gives it a tendency to move around more in high seas, which we will no doubt experience on this trip.

But what about the science? As we travel, the ship will be collecting all sorts of data. Meteorological things like pressure, temperature and wind speed are a given, but we’ll also be recording bathymetry (water depth) data to map the sea floor. More about that later though.

On this particular adventure there are three groups of people: The crew, who take care of operating the ship, the Ocean Bottom Seismometer (OBS) engineers, who will oversee instrument deployment and the science team, which is us. This makes about 45 in total.

To be honest the science team is probably the least useful of these groups when it comes to activities aboard, but it’s our job to help out where we can and stay out of the way otherwise!

Testing the winch. The UFO-like object being lowered into the sea is a TRM, a trawl resistant cover for a shallow-water seismometer

Back to the important questions though: What are we actually doing here? And why do it in Southeast Alaska? Much more detailed answers to these questions will probably be given as this blog evolves, but here’s the primer.

The main goal of this cruise is to deploy 48 Ocean Bottom Seismometers (OBS) and 3 Acoustic GPS (GPS-A) sensors, the data collected by which will be used by seismologists to understand the subduction zone offshore Alaska and the earthquakes that happen there. The OBS instruments will sit on the sea floor until the summer of 2019, constantly recording vibrations caused by earthquakes and other seismic sources. We’ll only get to see this data when the instruments are recovered next year. The GPS-A sensors will be used to measure the tectonic motions of the seafloor, which will help us understand earthquake hazards in this area.

Map showing earthquake activity in Alaska. South-Central Alaska is one of the world’s most tectonically active places. Source

Alaska is one of the world’s most seismically active regions. The second largest earthquake in recorded history (the M9.3 1964 Prince William Sound event) occurred off the south coast, not far from Seward. The state is also a site of volcanic activity, active mountain building and onshore fault motions that can also lead the large earthquakes (e.g. the M7.9 2002 Denali event). All of this activity is because of ongoing subduction of the Pacific plate beneath the North American plate. Stay tuned to this blog for future posts about Alaska tectonics and why it’s such an interesting place to study.

Robert Martin-Short, UC Berkeley Seismic Lab


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