Imaging the Sources of Great Alaskan Earthquakes

Imaging the Sources of Great Alaskan Earthquakes
Researcher: Donna Shillington
Student Blog: Team Diebold goes to Sea

A major tectonic boundary on the seafloor off Alaska has produced fatal earthquakes and tsunamis similar to the recent one in Japan. In 1964, the second largest quake ever recorded happened here, and other parts of the fault may be building energy for another event. Scientists from Lamont-Doherty Earth Observatory are aboard the research vessel Marcus G. Langseth to better understand what causes these quakes, which will help assess the hazard for Alaska and beyond. Follow Lamont seismologist Donna Shillington from the field.

Returning From Sea to Dutch Harbor

by | 8.8.2011 at 4:37pm
Shishaldin volcano

At 6:30 am on August 5, the R/V Langseth pulled into port in Dutch Harbor, marking the end of our very successful research cruise. Our steam into port from our study area involved a trip through Unimak pass and beautiful views of Aleutian volcanoes, including majestic Shishaldin. Many things are required to make a research [...]

Swimming in Data Offshore Alaska

by | 7.31.2011 at 9:22pm
Seafloor faults imaged by bathymetric mapping

Although we still have ~3 days of data collection aboard the R/V Langseth to go before we pull in our equipment and head for port, we are already drowning in beautiful seismic data. Following each pulse from the air gun array, the two 8-km-long streamers listen for returning sound waves for 22 seconds. This is [...]

Boring Days at Sea are a Blessing

by | 7.24.2011 at 7:23pm | 1 Comment
Humpback observed from marine mammal observation tower on Langseth (picture courtesy of PSOs)

For the last nine days, we have been underway acquiring seismic reflection data to study a plate tectonic boundary offshore Alaska with the R/V Marcus G. Langseth. Now that the initial excitement of deploying all of our seismic gear and watching the first sound waves arrive on our two 8-km-long streamers has faded, we have [...]

Collecting Data Offshore Alaska, But Just Barely

by | 7.18.2011 at 4:23pm
P1000747

One of the core objectives of our project is to image the part of the plate tectonic boundary that locks up and then ruptures to produce great earthquakes. To examine deep parts of the interface between the Pacific plate and the North American plate in the Aleutian subduction zone, we need to go as close to the coast as possible. This is easier said than done.

Unspooling Miles of Seismic Streamer Near the Shumagin Islands

by | 7.14.2011 at 6:07pm | 2 Comments
Seismic streamer with a 'bird' being deployed into the ocean

On July 11, we marked the successful completion of the first phase of our project and embarked on the second. Part 1 involved deploying ocean bottom seismometers and recording air-gun-generated sound waves. We successfully retrieved all of the OBS’s, and the data that they recorded look very exciting at first blush (and contain some surprises!).

Summoning ocean bottom seismometers from the deep

by | 7.8.2011 at 1:39am | 2 Comments
P1000585

After leaving our seismometers on the seafloor offshore Alaska for a few days to record sound waves generated by the air guns of the R/V Langseth, we returned to collect them. The recovery of OBS always involves a certain amount of suspense.

Deploying Ocean Bottom Seismometers off Alaska

by | 7.4.2011 at 10:18am | 2 Comments
obs_deploy

On July 2, we finished deploying over twenty ocean-bottom seismometers as a part of our marine expedition to study a major tectonic boundary offshore Alaska. Ocean bottom seismometers (OBS’s) are autonomous instruments that sit on the seafloor and record sound waves traveling through the earth and the water. Floats made from glass balls and syntactic [...]

Heading to Sea off Alaska Aboard the R/V Langseth (at last)

by | 6.30.2011 at 10:44pm
The R/V Langseth in port in Kodiak

Yesterday evening, we left Kodiak aboard the R/V Marcus G. Langseth and began our 38-day-long research cruise offshore Alaska. As we left port, we were treated to clear skies, calm seas and spectacular views of Kodiak – dark grey mountains tipped with snow emerging from the lush green landscape. Although Kodiak offered beautiful sights and [...]

Finishing Up Onshore and Heading Offshore

by | 6.24.2011 at 7:09pm
I admire a small earthquake recorded at our Nelson Lagoon station

Seven days and eleven flights after we arrived in Alaska, we finished deploying our seismic stations onshore.  Our final constellation of stations differs a little from our original plan (as always happens with field work), but achieves our main goal of instrumenting the part of the Alaska Peninsula that is nearest to our planned offshore [...]

Installing Seismic Gear On The Beautiful (But Challenging) Alaska Peninsula

by | 6.22.2011 at 2:23pm
Katie and Doug install station in Port Heiden

Every field location comes with logistical hurdles, and the Alaska Peninsula is no exception. Weather, wildlife and modes of transport pose the greatest challenges. We are hardly the first scientists to encounter these: Lamont-Doherty Earth Observatory has a long, rich history of collecting seismic data in this region (e.g., Shumagin Seismic Network, which ran for [...]