Alaska experienced a busy year underground in 2014, according to experts who record the state's earthquakes.
The Alaska Earthquake Information Center detected 40,686 quakes in the state and bordering parts of Canada, significantly more that the previous high of nearly 32,000 in 2003, the Fairbanks Daily News-Miner reported.
In 2013, 28,000 earthquakes were detected with the center's seismometer network.
"We've blown away those benchmarks," said state seismologist Michael West. "There's never been a year where we identified 40,000 earthquakes in a year."
The number is easily the most in the last decade or so, he said, but it's hard to make comparisons to earlier years.
"The further we go back the less information there is," he said.
Most of the 2014 earthquakes were not felt by people, West said, and were in the range of magnitude 2 or 3.
With more than 400 recording stations across Alaska, and up-to-date maintenance, the health of the seismic network is better than ever, West said.
Technological advances in instruments and software also have improved the center's ability to detect earthquakes, he said.
Those two reasons don't explain the increase, however.
"Then the third one, which is actually of interest, is the Earth itself," West said. "Even when you strip away those other two, there really have been a disproportionate number of earthquakes in Alaska in the past year."
A lot of small earthquakes are aftershocks from big quakes, he said.
The significant 2014 quakes include the Noatak-area "swarm," five earthquakes greater than magnitude 5 from April to June in the northwest Brooks Range.
A magnitude 7.9 quake, the largest since 2002, on June 23 struck the Rat Islands. A magnitude 6 earthquake erupted July 17 under Seward Glacier in the Saint Elias mountains. Another magnitude 6 quake struck July 25 in southeast Alaska's Palma Bay.
On Aug. 30, a magnitude 5.2 quake hit near Minto and was felt in Fairbanks. On Sept. 25, a magnitude 6.3 quake near Skwentna was felt in downtown Anchorage about 80 miles away.