This is the Biggest and Most Damaging Earthquake in Shake Idaho’s History


Idaho is no stranger to earthquakes since it sits on a major fault line that runs across the Rocky Mountains. However, on March 31, 2020, Idaho witnessed its strongest earthquake in over four decades, with a magnitude 6.5 quake jolting the state’s central region.

The quake was felt by millions of people in Idaho, Montana, Utah, Nevada, and even Canada, causing minor damage and power interruptions in certain regions. But how does this earthquake compare to the largest one ever recorded in Idaho?

The Borah Peak earthquake of 1983

The answer is the Borah Peak earthquake, which struck on October 28, 1983, and registered a staggering 7.3 on the Richter scale. This quake was not only the greatest ever recorded in Idaho but also the largest in the contiguous United States since California’s Kern County earthquake of 1952.

The Borah Peak earthquake was so violent that it left a 21-mile-long fault scarp, or visible breach in the earth’s surface, that reached 14 feet in height. The earthquake also caused multiple landslides, rockfalls, and avalanches in the hilly area.

The Borah Peak earthquake caused significant damage and killed two people in the communities of Challis and Mackay, which were closest to the epicenter. According to the Idaho Geological Survey (IGS), 11 commercial structures and 39 residential dwellings were severely damaged, while over 200 buildings sustained moderate damage.

The earthquake also caused damage to multiple bridges, roads, pipelines, and dams, as well as disruptions in water, sewage, and electricity systems. The overall cost of the damage was estimated at $12.5 million, which is approximately $33 million today.

Impact of Earthquakes in Idaho

The Borah Peak earthquake was an uncommon and intense occurrence, although Idaho has had many more major earthquakes throughout its history. Since 1900, Idaho has seen 14 quakes of magnitude 6.0 or higher, as well as 51 quakes of magnitude 5.0 or higher, according to the United States Geological Survey.

The majority of these earthquakes struck the state’s center and eastern regions, where the fault line is more active. However, several earthquakes were felt in the state’s western and southern regions, where the fault line meets with other geological structures.

Earthquakes pose a significant risk to Idaho’s people and infrastructure, particularly in remote and mountainous areas with low population density and less severe construction requirements. Earthquakes can also produce secondary hazards such as landslides, liquefaction, floods, and fires, which can result in additional damage and deaths.

Furthermore, earthquakes can have long-term consequences for the ecosystem, including modifying the terrain, altering groundwater flow, and emitting greenhouse gases.

The Future of Earthquake Preparedness in Idaho

Given Idaho’s high seismic potential, it is critical that the state enhance its earthquake preparedness and resilience. The IGS and the USGS collaborate to monitor and analyze Idaho’s seismic activity and fault structure, as well as deliver accurate and timely information to the public and authorities.

The state and municipal governments are also taking steps to lessen the earthquake risk, including upgrading building rules, adapting essential buildings, holding emergency exercises, and educating residents.

However, there is still an opportunity for improvement because many Idahoans are uninformed of the earthquake risk or how to safeguard themselves and their property. According to a 2017 poll done by Boise State University, just 15% of Idahoans had taken part in an earthquake drill, and only 18% had secured their furniture and appliances to keep them from toppling during an earthquake. Furthermore, only 37% of Idahoans had an emergency package and 40% had a family communication plan in the event of a crisis.

As a result, Idahoans must take proactive actions to prepare for the next major earthquake, which will occur when not if. Idahoans may take the following easy and effective actions:

  • Find out what kinds of earthquakes can happen in their area and how to spot the signs of one.
  • Make a plan with their family and friends for how to get in touch with each other, where to meet up, and what to do in case of an emergency.
  • Put together an emergency kit with enough food, water, medicine, and other things to last at least 72 hours, and keep it somewhere safe and easy to get to.
  • Anchor their furniture and equipment and get rid of or move any heavy or flimsy things that could fall or break during an earthquake to make their home and workplace safer.
  • When they feel the shaking, they practice how to drop, cover, and hold on, as well as how to get out of the building safely.
  • Know what’s going on and do what the officials say before, during, and after an earthquake.
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