The entire house started vibrating, for what seemed like an eternity. In reality, it was just over 30 seconds. As my Labrador nervously paced my bedroom, my first thought was, “that train can sure rattle this tiny house.” Helena, Montana has westbound coal trains that speed through town at all hours of the day and night. Even though I am far enough from the tracks, sometimes it feel like my bed is shaking when it passes. But, on this evening, just past midnight, it wasn’t a train, it was a 5.8 magnitude earthquake with an epicenter just 40 miles from town.
After waking enough to realize it an earthquake, my mental processes were grasping at what to do next. “Head to the basement, wait no, that’s a tornado.” I was drawing a blank and instinct kicked in. I ran into my son’s room, who was still sleeping at the time, until I threw myself on top of him to shield him from any falling debris. Apparently, I’m a misguided hero. After the first tremor was over, I realized we should be hiding under the table. My son and I just lay in bed, wide awake, as we waited through two aftershocks, with similar intensity to the original earthquake.
Is It the Super Volcano?
As a geologist knowledgeable in the seismically active regions of my region, my biggest concern was – “it’s going to blow, the Yellowstone Super Volcano is going to blow!”
Fortunately, the information super highway was sitting next to my bed. I was able to determine that the epicenter wasn’t south of Helena in Yellowstone National Park, rather in the opposite direction. It was 40 miles northwest near a very small town, Lincoln, Montana.
It was a wild night and the next morning I heard tales of coworkers standing in the middle of the street in pajamas, not sure what was going on or what to do.
Over, the past month, there has been a significant increase in seismic activity northwest of Helena, and many of nights I am confused between the train and the earthquakes. In the past 30 days, according to the USGS map, there have been 60 recorded earthquakes with magnitudes greater than 2.5 near Lincoln Montana. This wins in the number of earthquakes in my region beating out the former champion in seismic activity, Yellowstone National Park, with a mere 15 earthquakes in the past 30 days greater than 2.5.
Let me explain a bit of the science behind earthquake measurements. The USGS – United States Geological Survey- monitors earthquake activity throughout the US and the world. The device that measures earthquakes is a seismometer and the measure that the USGS uses to measure the vibrations and intensity is the Richter scale. Generally speaking, an earthquake with a magnitude less than 2.5 is usually not felt, but can still be measured. Earthquakes greater than 2.5 to 5.4 are often felt and cause minor damage. They are quite common, with over 30,000 across the world each year. Earthquakes similar to the 5.8 magnitude near Lincoln occur less frequently, approximately 500 per year worldwide, usually resulting in some structural damage. Fortunately for humanity, the higher magnitude earthquakes, capable of mass destruction, are much less frequent with magnitudes greater than 8 occurring every 5 to 10 years.
The 5.8 magnitude Lincoln earthquake was felt by many and thankfully resulted in only minor damage and some broken ketchup bottles in the Lincoln store. Any potential damage due to earthquakes is already limited. There is low population density and a whole lot of nothing near Lincoln.
Should we be worried?
Could this increase in earthquake activity near Lincoln be a sign of something bigger to come? After all, this is the biggest earthquake in decades, and the strongest to hit the state in more than 40 years.
The last big earthquake that the older Montanan’s can remember was the Quake Lake earthquake of 1959. A 7.3 magnitude earthquake, near Yellowstone National Park, created a massive avalanche, killing 28 people and rearranging the hydrologic landscape into the current day Quake Lake. To compare, the 2010 earthquake in Haiti registered 7.0 on the Richter Scale.
This region is very capable of devastating earthquakes even though the location is so far away from plate boundaries. Generally, the higher magnitude earthquakes occur near plate boundaries. Haiti is located right on a plate boundary.
Mike Stickney, a seismologist at the Earthquake Studies Office with the Montana Bureau of Mines and Geology in Butte, said the quake was probably the strongest in Montana since October 1964 and was located along the axis of the intermountain seismic belt. He said the quake occurred on a strike/slip fault. This is a vertical fault where one side moves horizontally against the other, similar to the kind of movement experienced along the San Andreas Fault in California.
Intermountain Seismic Belt
A belt of seismicity known as the Intermountain Seismic Belt extends through western Montana and continues southward through Yellowstone Park, along the Idaho-Wyoming border, through Utah, and into southern Nevada. In western Montana, the Intermountain Seismic Belt is up to 100 km wide. A branch of the Intermountain Seismic Belt extends west from the northwest corner of Yellowstone Park, through southwestern Montana, into central Idaho. It has been the site of the two largest historic earthquakes in the northern Rocky Mountains, the August 18, 1959 Hebgen Lake, Montana, earthquake and the October 28, 1983 Borah Peak, Idaho, earthquake (M 7.3). Although it has been over four decades since the last destructive earthquake in Montana, small earthquakes are common in the region. They occur at an average rate of 7-10 earthquakes per day.
Is a Big Earthquake Likely?
You would have way better luck predicting the weather in a mountainous region than predicting earthquakes. The smaller earthquakes, while frequent, may be just that, small earthquakes. There is nothing static about our earth and whether we feel it or not, there is constant movement, extension and compression, and sometimes the crust needs to release some tension. This results in an earthquake. I’d rather the crust release little burps than to wait for the build-up of tension to an earthquake of mass destruction. Either way, it is beyond human control, and scientists do their best at measuring and predicting.
An earthquake can happen anywhere. There are known faults, active and inactive, and unmapped faults throughout the entire United States. It would be impossible to tell, without the use of a crystal ball, where or when the next big one is going to hit. What we do know – the chance of experiencing an earthquake increases near plate boundaries, or in my case, near the Intermountain Seismic Belt.
Let me know your thoughts on the recent increase in Earthquake Activity in the comments below!
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