Skip to main content
U.S. flag

An official website of the United States government

Lake sediments can unlock crucial information about past earthquakes, needed for seismic hazard modeling. USGS researchers and partners from the Woods Hole Oceanographic Institution deployed 10 seismographs in and around Skilak Lake, Alaska to learn more about past shaking events.  

Understanding the timing, size, and location of past earthquakes is key for assessing seismic risks and creating hazard models. In earthquake prone regions like Southcentral Alaska, lake sediments are proving to be an especially reliable indicator of past seismic events. 

yellow boat is towed behind bigger boat in blue lake and mountains in background
The float rig from which the seismographs were deployed on Skilak Lake, Alaska.
Unveiling Earthquake History at Skilak Lake, Alaska

Sediment cores from these lakes provide a detailed timeline of past seismic events. Geologists look for buried deposits from underwater landslides and turbidity flows triggered by earthquakes to determine when each event occurred.

To infer magnitudes and locations of older events, researchers need to know how lake basins respond to seismic waves arriving from different directions and earthquake sizes. The response of a lake basin to seismic shaking can be measured directly by installing seismographs in and around the basin.

Person sitting on floating equipment in the middle of a lake on a cloudy day, a mountain is in the background
The float rig supporting the seismographs was towed to the deployment site on Skilak Lake with Hannah Brewer (WHOI) on board.
Unveiling Earthquake History at Skilak Lake, Alaska

Combining the geologic and seismic observations enables researchers to extend the modern record of seismic events further back in time. 

Person sits on log with seismic equipment recording data in notebook
Nathan Miller (USGS) programing a land seismograph station.
Unveiling Earthquake History at Skilak Lake, Alaska

Instrument Deployment at Skilak Lake, Alaska

A team of USGS scientists, in collaboration with partners from the Woods Hole Oceanographic Institution Ocean Bottom Seismic Instrument Center, are aiming to create a record of past earthquakes from Skilak Lake on the Kenai Peninsula of Alaska. In May 2024, they deployed two seismographs on the bottom of the lake and eight seismographs on land around the lake. Each instrument will collect data there for about 1 year. 

The seismographs at the bottom of the lake were originally designed for use in the deep ocean. They weigh roughly 800 pounds and are typically deployed from large ships, so the research team needed to get creative to make them work for this effort. The scientists towed the seismographs to the lake and launched them from a flatbed trailer. On the water, they were supported by a float rig and towed by a small boat to the deployment locations where they were released and sank to the lake bottom. To recover them when the year is up, an acoustic pinger will be used to trigger the instruments to detach from an anchor.

At each land site, around 300 pounds of instrument components were transferred from the boat to shore, then carried to the sites. Installation involved digging holes for the post-hole seismometers and attaching a station box containing electronics and batteries. 

two people in red dry suits stand next to seismic equipment
Unveiling Earthquake History at Skilak Lake, Alaska
person with red life vest smiles for photo on boat in lake
Unveiling Earthquake History at Skilak Lake, Alaska
two people in life jackets smile for a photo out on the water
Unveiling Earthquake History at Skilak Lake, Alaska
man in green hat and blue jacket smiles for photo on boat
Unveiling Earthquake History at Skilak Lake, Alaska
scientists stand around yellow boat and red buoys on boat launch
Unveiling Earthquake History at Skilak Lake, Alaska
two people in red dry suits prep buoy in yellow boat while in the water
Unveiling Earthquake History at Skilak Lake, Alaska
Small research boat and inflatable boat with person in it on a lake with snowcapped mountains in the background.
Unveiling Earthquake History at Skilak Lake, Alaska
two people in red dry suits prepare buoys for deployment off of yellow raft
Unveiling Earthquake History at Skilak Lake, Alaska
Three people on land near lake, digging
Unveiling Earthquake History at Skilak Lake, Alaska
three people on boats in lake with snow covered mountains in background
Unveiling Earthquake History at Skilak Lake, Alaska
One person laying down and one kneeling next to the post in ground in marshy wooded area.
Unveiling Earthquake History at Skilak Lake, Alaska

The data collected from these seismographs will offer invaluable insights into how basin shape, sediment types, earthquake size, and location influence shaking intensity. This can enhance seismic hazard models, leading to more accurate risk assessments and better overall preparedness. 

 

landscape of boat sitting in lake with forest and mountains in the background
The R/V Lutris on Skilak Lake, Alaska.

Get Our News

These items are in the RSS feed format (Really Simple Syndication) based on categories such as topics, locations, and more. You can install and RSS reader browser extension, software, or use a third-party service to receive immediate news updates depending on the feed that you have added. If you click the feed links below, they may look strange because they are simply XML code. An RSS reader can easily read this code and push out a notification to you when something new is posted to our site.