Posted: Nov 3, 2013 4:02 PM by Matt Elwell - KBZK News
Updated: Nov 3, 2013 9:28 PM
Western Montana and Yellowstone National Park are certainly no strangers to earthquakes but this summer, several clusters of earthquakes were raising the eyebrows of scientists.
Our own meteorologist Matt Elwell has more.
This past summer marked an event that, in many respects, was normal around Yellowstone National Park - earthquakes.
But there was one exception - the sheer number of earthquakes that shook the area.
Nearly 130 small magnitude earthquakes occurred between September 10th and September 16th with different epicenters around the park.
These clusters of earthquakes are known as swarms.
Director of Earthquake Studies at Montana Tech, Mike Stickney said, "Earthquake swarm is swarm in indeed a cluster of earthquakes without one large outstanding event."
"Earthquake clusters kind of come in two flavors," he said. "One is a main shock-aftershock sequence where the main shock is a big earthquake followed by smaller earthquakes that typically die away with time. A swarm is just is a bunch of earthquakes without any outstanding earthquake. You get numerous earthquakes with similar magnitude in that sequence of events."
The rumbles that hit Yellowstone in September fall into the second category.
Stickney says, "They were actually very dramatic swarms if you were looking at seismograph centered near the epicenter of those earthquakes."
"There would be two, three or four-minute earthquakes going off every minute. Most of those were tiny magnitude one or smaller earthquakes," he said.
And what's more - visitors to the park may not have even known it was happening!
"Depending on how excited they were about the animals they might not have even noticed the earthquake.," Stickney said.
He says that there are fairly logical explanations and one of them isn't necessarily that Yellowstone's volcano is roaring back to life.
"There is good evidence to suggest that as magma, the molten rock at depth, cools, and crystallizes, it releases volatile water and gasses and those make their way out through fractures in the earth to the surface we see those as geothermal features in the park," he says.
"That fluid migrating through the earth's crust, we can think of that as lubricating some of those fractures and can produce some of those earthquakes. Probably those swarms in Yellowstone are related to the overall volcanic activity at depth and not necessarily indicating that something is getting ready to erupt," Stickney explains.
In fact, according to Stickney, it could be quite the opposite. The volcanic activity might just be quieting down, and those swarms may be just the result of gasses being released.
Stickney says that we know about 75 faults around western Montana that show evidence of seismic activity and only a handful of those faults have been studied in detail.
Scientist hope to be able to study them in more detail to understand how and why those faults might move.
For daily information on earthquakes and to track them yourself, visit this website.