The earthquakes within the Nenana Basin in Interior Alaska last longer and seem to be more powerful than quakes similar to those in other areas.
University of Alaska Fairbanks scientists are investigating the reasons.
Reverberation is all about the sound.
The beautiful lake and swamps that lie in the Minto Flats region is a huge bowl that’s full of gravel. UAF Geophysical Institute seismology professor Carl Tape said to imagine the flat terrain as the surface of the ocean. If you were to remove the water you’d be able to see fascinating things emerge.
“If you take away all the dirt that’s been dumped on the ground, you’ll find a number of interesting things to see,” he said. “These massive bowls of or depressions exist to the west of Nenana in the area at the point where there is a point where the Tanana River kind of takes the opposite direction and flows northwards, towards Minto Flats. Minto Flats area before it flows west, eventually reaching the Yukon. This means that in the area that is Minto Flats, what looks quite flat and normal on the surface is actually full of interesting features below.”
Tape collaborated with fellow graduate student Kyle Smith, placing 13 seismic monitors throughout the region for four years from 2015 until 2019. Between 2015 and 2019, they recorded information from 48 local and regional earthquakes. The monitors, the very first seismic stations to be installed within the Minto Flats, are part of the Fault Locations and Alaska Tectonics from Seismicity project that is funded with the National Science Foundation.
“That region hasn’t been extensively studied,” said Smith. “And We wanted to understand what the river’s movement was as people are looking to undertake a variety of projects in the region. Therefore, it’s helpful for us to understand what will happen if there’s a major earthquake.”
They discovered that seismic waves are amplified when they bounce across the sides and bottoms of the basin. This means that people living in the flats think that earthquakes are larger than they actually are. They also integrated discussions with Minto residents or work within Minto in their study.
The basin that lies west of Nenana and south of Minto is 56 miles long and 7.5 miles wide. It was filled over millions of years of sediments brought in by rivers of within the Alaska Range. Smith suggested that it may be the deepest of these basins in Alaska.
” It’s as deep as seven kilometers deep, which means there’s probably around four miles” Smith said.
This is higher than Denali is high.
The seismic monitors detected earthquakes that last longer on the gravel-filled basin than more hard ground. Each Tape and Smith noticed the observed distinction between Nenana Ridge, which is located under the Parks Highway, and the flats below.
“The Ridge between Nenana and Fairbanks If you drive on it you’re the rock. The ground is very different in this kind of rock that it does down to Minto Flats.”
“There’s certain areas where the unique topography beneath ground the huge basin Bowl amplifies the ground movement and can make it last for longer. We know this because we’ve put the stations on the ground to track seismic activity,” Tape said.
“The shaking is about 10 times less than when you were only a few feet from the area. This is pretty remarkable how significant the difference is due to whatever geological cause,” Smith said.
Smith was born on Smith was a member of the Navajo Nation, got his Ph. D. at UAF and is now in the process of completing a new research assignment in Taiwan.
Tape stated that a number of UAF scientists are looking at the area for research.
“But these same characteristics are the reason why to, as Doyon for example to explore exploratory wells as well as collect geophysical information due to the prospect of gas and oil,” Tape said.
While the study shows how the ground could be moved during certain types of earthquakes Smith warns that predicting earthquakes is still a ways from being accurate.
” We’ll have an idea of how much ground will shake from any earthquakes but it’s not enough to reveal when or where the earthquake will occur,” Smith said.
Smith will present a lecture on research conducted on the research at Sandia National Laboratories in May.
