Hawaiian-Emperor Seamount Seismic Experiment

A packed house for the finals of the ping pong tournament. Luan Nguyen squares off against Tim Kane. Following the successful completion of our program, we are transiting ~3000 km to port in Kodiak, Alaska.     This trip took us back across the date line and along the Aleutian Islands and Alaska Peninsula, where we were treated to glimpses of distant, rugged mountains shrouded in clouds. Our newly collected data has kept us very busy. The long trip enabled us to complete onboard processing of seismic and bathymetric data, discuss initial observations from the data and share our preliminary results with the rest of the Langseth ’s crew.   We are seeing all kinds of interesting and unexpected things in the data.  We may even get close to completing the cruise report before we come into port, which would a minor miracle. Mei Liu and her model OBS But the transit has also given us a chance for some recreation now that our main data collection dut...

Luan nabs a returning WHOI OBS Yesterday, we finished recovering 29 ocean bottom seismometers deployed along the Emperor Seamount Chain, thus completing our field program in the Emperor Seamount Chain.   We were blessed with a long period of excellent weather for collecting data on the 15-km-long seismic streamer and for most of the OBS recoveries.   Good weather is particularly important for the latter.   Despite all of the technology that enables us to put a seismometer on the seafloor in water depths of 6300 m (~19,000 ft!) and send them commands to come back to the ocean surface, our method of fetching them from the ocean onto the ship is quite basic, but still impressive! The ship’s mates drive this large vessel right up next to the floating OBS, and people reach out and hook the OBS from the starboard deck using a long stick!   We then use a crane to hoist them out of the water.   This procedure becomes much more difficult in rough weather. Maneuverin...

The main lab's view of the last seismic reflection data being collected. Overseeing  them are  drawings of Emperor Jimmu and Empress Suiko. Finishing the seismic reflection acquisition part of our experiment, we find ourselves south of Jimmu Guyot and near Suiko Guyot. The term ‘guyot’ refers to a flat top seamount that was first named by Harry Hess, a pioneer in developing our current understanding of plate tectonics. These features have a similar morphology to the plateaus found in the Western United States with both having a flat terrain on top that is raised above with surrounding areas often by steep slopes. The Hawaii-Emperor Seamount Chain is a great example of the formation of guyots along volcanic chains. Active volcanism is found on the youngest in the chain, currently at the Big Island of Hawaii which sits atop the central Hawaiian hotspot, a small spot in the plate that fuels the volcano from great depths. As the Pacific Plate slowly but steadily moves to t...

For the last few days, we have had calm seas and been ensconced in a thick fog much of the time. Right now, this doesn't pose any problems for our science operations - we are cruising along and acquiring seismic reflection data, which can illuminate the subsurface just fine, fog or no fog.  But the fog is starting to make everyone on the ship a little crazy!   Normally one is treated to expansive ocean views at sea, but instead we get to see this: The horizon is out there somewhere... Perhaps even more disconcerting, the ship sounds a special fog horn at regular intervals to alert other ships that we have limited maneuverability since we are towing equipment. It consists of one long horn followed by two shorter ones. It is very loud.  Everyone on the ship will tell you that this horn must be located right outside their  cabin. We can live with it for now, but soon we will transition back to OBS work. When its time to pick them up, it would be super helpfu...

Our expedition is moving along steadily. We have now completed collecting both wide-angle and seismic reflection data for our first profile. The Langseth is cruising toward our second line of survey which is about two days away (13hrs from now). In the past few days, we have had some very exciting experience with seismic acquisition including an opportunity to see how a hydrophone streamer was deployed into the water, 15 km of it.   The streamer is a carrier of hydrophones which we use to record the sound wave signals generated by our airguns that were reflected back to us from the subsurface. We have a set of hydrophones place every 12.5 m along the streamer. As watchers on the earliest shift of the day we got to spend a field day on the streamer deck and joined in with the crew to learn about streamer deployment and all of the advanced technologies that come with it. Putting out a 15-km-long line of hydrophones into the ocean is no trivial job. We were tasked with assem...

The streamer disappearing into the misty horizon. We already finished the first seismic reflection line! Deploying the streamer was a lot of work, but definitely worth it. 15 kilometers of hydrophones will allow us to identify more deeper structures, like the moho. Mei releasing an XBT into the ocean. While collecting the data, we had to keep an eye on the streamer tension, the multibeam bathymetry recording - like we always do - and we had to release some XBT's, which are instruments used to measure the water column temperature. This is important information for the bathymetry data and operation of equipment, but also for the seismic oceanography studies that Will has been working on. As scientists, we spend a lot of time in the comfy main lab (cleaning the multibeam files haha), so it's a refreshing experience to go out to release the XBT's. It's super cold outside and my shift goes from 2am to 10 am, so this time - as well as when we were deploying the O...

Chris snags WHOI OBS under Tim's watchful eye. It’s been a busy week! After we finished deploying 28 ocean bottom seismometers on the seafloor along a ~500-km-long profile across Jimmu Seamount in the Emperor Seamount Chain, we steamed back down the line creating seismic sources with the specialized seismic source array of the R/V Langseth .   We then retrieved all of the OBS. Sound waves from the seismic source array travel up to ~20 miles below the seafloor, and then bend back towards the surface. The returning sound waves are recorded by the ocean bottom seismometers, which are very sensitive and detect very small vibrations at the seafloor. We can model the paths of sound waves through the earth and the time it takes them to travel along those paths to image geological structures deep below the Emperor Seamount Chain, which is one of the main objectives of our study. While we were creating sound sources along the line, Valeria and Luan did some tests of ho...