Since Idaho is located on a major fault line that passes through the Rocky Mountains, earthquakes are common there. On March 31, 2020, a magnitude 6.5 earthquake rocked the middle portion of Idaho, causing the state to feel its biggest tremor in almost forty years. Millions of people in Idaho, Montana, Utah, Nevada, and even Canada felt the tremor, which also caused some minor damage and power disruptions. However, what is the difference between this earthquake and the largest known earthquake in Idaho?
The 1983 Earthquake at Borah Peak
The earthquake that struck Borah Peak on October 28, 1983, registered a massive 7.3 on the Richter scale. Not only was this the biggest earthquake in Idaho history, but it was also the biggest in the contiguous United States since the 1952 Californian Kern County earthquake. The Borah Peak earthquake was so strong that it left behind a fault scarp, or visible fracture on the earth’s surface, that stretched 21 miles and rose to a height of up to 14 feet. In the hilly area, the earthquake also caused multiple avalanches, rockfalls, and landslides.
The communities nearest to the epicenter, Challis and Mackay, suffered significant damage and lost two residents as a result of the Borah Peak earthquake. The Idaho Geological Survey (IGS) reports that over 200 buildings had moderate damage, while 11 commercial buildings and 39 individual residences sustained serious damage. In addition, the earthquake caused disruptions to water, sewage, and electricity services and destroyed several bridges, roads, pipelines, and dams. It was projected that the damage would cost $12.5 million in total, or over $33 million in today’s money.
The Effects of Idaho Earthquakes
Although the earthquake on Borah Peak was an uncommon and severe occurrence, Idaho has seen numerous other notable earthquakes throughout its history. Since 1900, Idaho has experienced 51 earthquakes of magnitude 5.0 or higher and 14 earthquakes of magnitude 6.0 or higher, according to the U.S. Geological Survey (USGS). The state’s eastern and central regions, where the fault line is more active, saw the majority of these earthquakes. But the state’s western and southern regions, where the fault line meets with other tectonic structures, have also seen occasional earthquakes.
Idaho’s infrastructure and population are seriously at risk from earthquakes, particularly in the state’s rural and mountainous regions where building rules are laxer and population density is lower. Secondary hazards that can result in further damage and mortality include landslides, liquefaction, flooding, and fires. These can also be triggered by earthquakes. In addition, earthquakes have the potential to release greenhouse gases into the atmosphere, change the flow of groundwater, and change the terrain over the long term.
Idaho’s Prospects for Earthquake Preparedness
Idaho has a high seismic potential, therefore strengthening its resilience and preparedness for earthquakes is crucial. In order to accurately and promptly educate the public and the authorities about Idaho’s seismic activity and fault structure, the USGS and IGS are collaborating. In order to lower the risk of earthquakes, the state and local governments are also putting in place a number of measures, including revising building rules, retrofitting important facilities, holding emergency drills, and educating the public.
There is still space for improvement, though, as many Idahoans do not know how to safeguard their home and themselves from earthquake threats. Just 15% of Idahoans had taken part in an earthquake drill, and only 18% had secured their appliances and furniture to keep them from falling during an earthquake, according to a 2017 Boise State University poll. In addition, only 40% of Idahoans had a family communication plan in case of a disaster, and only 37% had an emergency pack.
In Summary
Since the Borah Peak earthquake of 1983—which was the greatest earthquake ever recorded in Idaho—the magnitude 6.5 earthquake that struck the state in 2020 was the largest. The two earthquakes showed how vulnerable and seismically active Idaho is, as well as how important it is to improve resilience and readiness for earthquakes. Idahoans may lessen the effects of future earthquakes and recover more quickly by reflecting on the past and acting now.
