Tag Archives: seismometers

Cascadia Initiative on the RV Oceanus – 2013

Poor Internet connections prevented Bill from live-blogging the 2013 cruise, though he was able to capture some video (below) that provides an idea of what working conditions can be like at sea. You can learn about the season’s objectives and accomplishments on the Cascadia Initiative 2013 Cruise page.

Videos from the 2013 cruise:

Bird’s eye view of the recovery process:

OBS Recovery 2:

SIO OBS Night Recovery:

Deepest Recovery

Monday, July 16, 2012

The weather today cooperated with the successful recovery of three of our deepest deployed Abalone seismometers. The seas were calm, with 3 to 6 foot swells. The wind was out of the north, picking up to 11 knots as evening approached.

The depth of the seismometers’ deployment directly effects their recovery time. After an acoustic signal from the New Horizon is sent down to the Abalone’s release wire, we wait 7 to 8 minutes for the wire to burn through. We actively range on the Abalone as it ascents. Since the ship is stationary, the amount of time for the acoustic signal to travel up from the seismometer steadily decreases. The three Abalones that we recovered today (J43, J44 and J36) were deployed in depths ranging from 2654 meters to 2821 meters. The deepest seismometer (J36) that was signaled at 21:26, didn’t reach the surface until 22:10, and required a 44-minute ascent time. About twenty feet from the surface, a pressure-activated strobe is activated. There is also an orange flag on top of each Abalone, but since this particular recovery was at night, we relied on the strobe in order to navigate the ship into close proximity.

Abalone with signal flag and strobe light

Once sighted and illuminated by spotlight, the New Horizon maneuvers to bring the Abalone along its starboard side. This is a delicate procedure, requiring a slow forward speed and bow thrusters so that we can bring the ship close enough to attach a tag line to the top of the Abalone.

One of us uses a telescoping pole with detachable grab hook attached to the tag line. Given the roll of the ship, large ocean swells and the vertical bobbing of the Abalone, this procedure can be very challenging. If we are unsuccessful, the New Horizon must turn into the sea for another attempt.


Detachable hook on telescoping rod
Attaching tag line 

Once the first tag line is attached, another line from a telescoping pole and detachable grab hook is attached to the Abalone. The other end of this line is connected to the deck crane, which does the heavy lifting. Even after leaving the 300-pound weight on the ocean floor, the Abalone weighs over 550 pounds.

Retrieval Crane 

Immediately after the crane lifts the Abalone from the sea surface, another tag line is attached to its bottom. By maintaining tension with the first and third lines, the Abalone is prevented from colliding with the ship. The crane continues to lift, then turn aft, positioning the seismometer of the deck. Tag line tension is eased as the crane slowly lowers the Abalone and is secured to the deck of the New Horizon.

Keep the tag line taut
Abalone on deck

All of the data that the seismometer collected during its months on the ocean bottom is stored in the red data logger. The data logger is removed from the Abalone and quickly taken into the ship’s science lab to begin analysis.

Tossed at Sea

Sunday, July 15, 2012

It’s been another full day. We recovered the Abalone seismometer J65 slightly after midnight (00:10) from 165 meters of water. After moving north, the weather deteriorated. Offshore the Washington side of the Juan de Fuca strait the winds rose to more than 35 knots, coming in from the Northwest. The seas were high and steep, but we managed to recover YiM2 at 04:45 from 139 meters.:

The darkness added to the challenge, as you might expect. We cruised on to the next Abalone recovery site, but the sea conditions were too hazardous to attempt it. Instead, we continued moving north through the heavy weather.

Attempting to sleep in conditions such as these are difficult. The pitch and roll of the New Horizon keeps you awake, in spite of exhaustion. An added hazard is being tossed from your bunk to the metal deck. I placed my survival suit under the outer side of the mattress, creating somewhat of a solid hammock. To insulate myself, I put blankets between the bulkhead and my body. Needless to say, we didn’t get much sleep:

Because of the weather and our reduced cruising speed, it took us until 13:50 to arrive at Y1M1. When we recovered this Abalone, it was covered with spiny sea stars. We recovered the fourth Abalone of the day (J73) at 17:46 from 143 meters.

Heading north on Saturday

Saturday, July 14, 2012

Today we recovered three Abalone seismometers. The first one was Y1M5 (see chart for location) at 07:30 from 828 meters down. The second seismometer (J57) was much shallower. At only 56 meters deep, its structure was covered with barnacles, anemones and a couple of sea stars. The next seismometer (Y1M4) was recovered from 563 meters of water at 20:20.


Anemones on J57

As the day progressed, the wind and sea flatten somewhat, permitting observation of marine mammal activity. During the morning we spotted two humpback whales (Megaptera novaeangliae) lunge feeding, possibly on herring. Later (~19:30), we had the good fortune to watch a large pod (~200) of Pacific white-sided dolphins (Lagenorhynchus obliquidens) swimming with another pod (~100) of Pacific right whale dolphins (Lissodelphis borealis). They could be clearly identified by their lack of a dorsal fin and torpedo-like breaching behavior.



Friday the 13th – First night at sea

The fifteen instruments to be recovered were some of those that were deployed from the October voyage of the Wecoma. These are the Scripps Institute of Oceanography “Abalones”. Abalones are trawl-resistant, three component, battery powered ocean bottom seismometers, capable of being deployed in water depths of 50 to 6000 meters. We are recovering them via an acoustic release. After cruising to the proper latitude and longitude, an acoustic signal is sent down from the ship to “wake up” the Abalone’s acoustic release. The Abalone acknowledges by sending back its own acoustic signal. We then send a signal down to the acoustic release burn wire. The burn wire is an alloy of nickel and chromium. When an electric current is passed through it, the burn wire begins to oxidize. After about seven and a half minutes, the Abalone separates from its steel ballast and floats to the surface at about 60 meters per minute.

The first Abalone slated for recovery (Y1M7) was deployed in 1356 meters of water. After its 22-minute ascent, the strobe from the first Abalone was sighted at 22:05. The rough seas and high wind complicated recovery.  The deck crew missed the first pass, and the New Horizon had a difficult time keeping the floating Abalone along its starboard side. Eventually we secured our first recovery to the deck at 22:45.

We will cruse through the night to our second station (Y1M5).

Off the coast of Washington

Wednesday afternoon, October 19th – Off the coast of Washington at the edge of the continental margin

We just deployed another Cascadia seismometer. It will take 65 minutes to reach the ocean floor, 2630 meters below. It will take another hour to conduct the acoustic survey, as the Wecoma cruises in a kilometer and ½ circle overhead.

Ready to be released


Wecoma’s crane is lifting the seismometer over the side


It takes at least 5 crew members to deploy a seismometer

Wednesday’s Sunrise

The weather has deteriorated somewhat, but is still serviceable.  We deployed two seismometer last night and another one this morning. Since we are in deeper water, it takes longer for the seismometer to reach the bottom.  A acoustic survey is immediately conducted to determine its exact location in three dimensions; latitude, longitude and depth. The Wecoma circles the seismometer location as the acoustic release sends signals to the ship.

Wednesday’s Sunrise