Some may not believe this, but Montana is one of the most earthquake-prone states in the nation. The Great Montana Shake out says earthquake activity in Montana usually happens in the state’s mountainous western region since it lies in the intermountain seismic belt. While earthquakes with a magnitude of 8.0 are less likely, Montana earthquakes can range as large as 7.5.
The Hebgen Lake earthquake in Southwestern Montana that occurred in the late 1950s was the largest historic earthquake in Montana, with a 7.3 magnitude. The earthquake resulted in 29 fatalities and roughly 11 million dollars in damages. It also caused about 18 miles of surface faulting with two major faults on the lake’s northeast side. The earthquake dropped the lake’s basin down to about 22 feet.
The earthquake was felt in Washington, Canada, North Dakota, and Utah. One of the most significant disastrous effects of the quake was the triggered landslide that came down from the South Wall of the Madison Canyon near the lake. This incident became the largest triggered landslide in North America. The Hebgen Lake also caused a large wave underneath the lake that caused damage to the Hebgen Dam.
Another significant earthquake happened in Helena, Montana, more than 80 years ago. What started as a few small tremors became a series of several hundred earthquakes over the month of October. The three most damaging earthquakes were a 5.8 – 6.0 earthquake magnitude. Several people were injured, and two died as a result of falling bricks from buildings.
The earthquakes resulted in an estimated 3 million dollars of property damage, with Helena high school suffering the most. One of the largest earthquakes was felt across 230,000 miles of land, including in areas of Western Montana, Wyoming, Idaho, and even southern Canada. The aftermath of the Helena earthquake proved to locals that they do not only happen in California and Alaska, which was a common belief at the time.
The best way to stay safe during an earthquake is to drop to the ground, take cover by getting underneath something sturdy like a table or desk, and hold onto the sturdy object until the shaking stops.