Glacial Activity Measured By Earthquake Monitoring Systems Can Be Very Useful
The melting of glaciers has long been associated with earthquakes. But frequent ice melts in Alaska though captured by seismic networks, are not considered particularly important. But according to state seismologist Michael West, the current earthquake monitoring system could be "tweaked" to target the dynamic movement of the state's glaciers. He will present his research today at the annual meeting of the Seismological Society of America (SSA), according to a press release Thursday.
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"In Alaska, these glacial events have been largely treated as a curiosity, a by-product of earthquake monitoring," said West, director of the Alaska Earthquake Center, which is responsible for detecting and reporting seismic activity across Alaska.
The Alaska seismic network was revamped in 2007-08, which improved its ability to record and track glacial events. "As we look across Alaska's glacial landscape and comb through the seismic record, there are thousands of these glacial events. We see patterns in the recorded data that raise some interesting questions about the glaciers," said West.
When large of chunks of ice break off from the leading edge of a glacier, in a process called calving, the Alaska Earthquake Center's monitoring system automatically records the event as an earthquake. Analysts monitor these records and eliminate these signals to have a clear record of earthquake activity for the region. But the discarded data may be a gold mine of information according to West.
"We have amassed a large record of glacial events by accident," said West. "The seismic network can act as an objective tool for monitoring glaciers, operating 24/7 and creating a data flow that can alert us to dynamic changes in the glaciers as they are happening." It's when a glacier is perturbed or changing in some way, says West, that the scientific community can learn the most.
Since 2007, the Alaska Earthquake Center has recorded more than 2,800 glacial events along 600 km of Alaska's coastal mountains. The equivalent earthquake sizes for these events range from about 1 to 3 on the local magnitude scale.
The majority of recorded quakes are a result of calving but there are other reasons for increased quake activity as well. For example the end of each glacier, where the ice meets the ocean known as the glacier's terminus or snout, behaves differently. Also, variations in the climate also impacts the glaciers movement creating an expected seasonal cycle in seismic activity. But West and team have seen unusual activity too.
In mid-August 2010, the Columbia Glacier's seismic activity changed radically from being relatively quiet to noisy, producing some 400 quakes to date. These types of signals from the Columbia Glacier have been documented every single month since August 2010, about the time when the Columbia terminus became grounded on sill, stalling its multi-year retreat.
This observation made West aware of the importance of the data collected by the Alaska Earthquake Center. "The seismic network is blind to the cause of the seismic events, cataloguing observations that can then be validated," said West, who suggests the data may add value to ongoing field studies in Alaska.
Of the numerous glacier studies conducted in Alaska, most of them concentrated on specific areas of the glacier over short periods and not on the entire glacier over a longer duration.
West suggests leveraging the data stream may help the scientific community observe the entire glacier complex in action or highlight in real time where scientists could look to catch changes in a glacier.
"This is low-hanging fruit," said West of the scientific opportunities waiting to be harnessed from the data.
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