Earthquake Swarm Rocks Yellowstone
It was recently reported that a very rare triple swarm of earthquakes rocked Yellowstone National Park.
In fact, Bob Smith, a geophysics professor out of the University of Utah, says he has never seen even two swarms occur together before in all the 53 years that he has been monitoring seismic activity. Now, he he’s seen three.
An earthquake swarm, seismologists say, is an event where a sequence of earthquakes occurs in a limited geographic area over a short period of time.
Speaking about the event, Smith called it “remarkable,” asking, “How does one swarm relate to another? Can one swarm trigger another and vice versa?”
No answers are available to Smith’s questions, however, because simultaneous swarms haven’t been detected before.
Smith says he believes that at least two of the swarms are probably related to each other though.
The three swarms hit in the following areas: Lewis Lake, the Lower Geyser Basin and the northwest part of Norris Geyser Basin.
Earlier this month, on September 15, the largest earthquake to rock Yellowstone in over a year occurred about six miles north of the Old Faithful Geyser. Its magnitude was about 3.6 at its epicenter. It takes a magnitude of about 3.0 for people to feel it, a Yellowstone representative named Al Nash told the Jackson Hole News & Guide.
The recent swarms of earthquakes began on September 10 and finished up on September 16.
The University of Utah put out a statement saying that altogether 130 earthquakes with magnitudes ranging from 0.6 to 3.6 occurred in the area, with most of them being located in the Lower Geyser Basin. But, including many smaller events which were not detected, there were many more quakes than this.
The recent swarms produced four earthquakes which, although they were not large, were significant enough in size to be felt.
The first, which had a magnitude of 3.5, happened on September 13, about 17 miles northeast of West Yellowstone, Montana. The next two tremblors to be felt occurred early on the morning of September 15 with magnitudes of 3.2 and 3.4 respectively. These two occurred in rapid succession, with one being detected at 5:10 AM and the other at 5:11 AM. The quakes happened about 15 miles southeast of West Yellowstone. The largest earthquake recording during the swarm, a 3.6, was measured nearby about 4 1/2 hours later.
According to Nash, a strong enough earthquake, like the 7.3-7.5 quake that shook the Hebgen Lake area in 1959, has the potential to change the activity of the geysers in the area. And, in fact the 1959 quake did. It caused nearly 300 features to erupt, included 160 where there were no previous records of geysers. None of the current earthquakes were powerful enough to create these types of changes, however.
Smith says he believes that the current swarms of earthquakes may, in fact, be related to the 1959 earthquake. “We think that much of the seismicity is still aftershocks from that event in 1959. It can go on for hundreds of years.”
Usually only about half a dozen earthquakes occur each year in Yellowstone, Smith noted, so it is quite unusual for this level of swarm activity to rock the park.
Written by: Nancy Schimelpfening
http://guardianlv.com/2013/09/earthquake-swarm-rocks-yellowstone/