Earthquakes risk in South Dakota

Earthquake Risk in South Dakota

South Dakota is located in the stable interior of the North American plate, far from the active plate boundaries that cause most of the world's earthquakes. According to the USGS Earthquake Hazards Program, the state has a relatively low seismic hazard compared to regions like California or Alaska. The South Dakota Office of Emergency Management also recognizes that while the risk is low, it is not zero. The state has experienced occasional small earthquakes, but no major damaging events in recent history.

Geography plays a key role: South Dakota is far from the New Madrid Seismic Zone in the central U.S. and the Intermountain Seismic Belt in the West. However, there are minor fault lines in the state, particularly in the western and central regions. The Black Hills area, for example, has seen minor seismic activity. But overall, the entire state shares a similar low risk. Earthquakes do not have a 'season' – they can occur at any time of year, though they are not tied to weather patterns. The most exposed areas would be those near any minor faults, but even there, the chance of a strong quake is very low.

The USGS National Seismic Hazard Maps show that the risk is relatively uniform across South Dakota, with slightly higher hazard in the western part of the state near the Black Hills and along the Missouri River. However, even these areas have a very low probability of damaging earthquakes. The state's emergency management agency encourages residents to focus on general disaster preparedness, which covers earthquakes along with other hazards like tornadoes and floods.

State emergency managers emphasize an all-hazards approach to preparedness, meaning the same steps that help you get ready for other disasters (like severe storms or floods) also apply to earthquakes. Because the risk is low, most South Dakotans will never experience a damaging earthquake, but knowing what to do can prevent injury and panic if one does occur.

How Earthquakes Affect Homes in South Dakota

Even a moderate earthquake can cause damage to homes, though in South Dakota the likelihood of a strong quake is very low. Typical earthquake damage includes cracked foundations, walls, and ceilings; broken windows; and toppled furniture or appliances. Older homes, especially those with unreinforced masonry (brick or stone) chimneys or walls, are more vulnerable. Homes built on soft soils or fill may experience more shaking than those on bedrock.

In South Dakota, the most common housing stock includes wood-frame homes, which generally perform better in earthquakes than unreinforced masonry. However, any home can suffer damage if the shaking is strong enough. Non-structural damage—like items falling off shelves, water heaters tipping over, or gas lines rupturing—can also be costly and dangerous.

Insurance considerations: Standard homeowner's insurance policies typically do not cover earthquake damage. In South Dakota, because the risk is low, many insurers may not even offer earthquake coverage as an add-on. If you want protection, you would need to purchase a separate earthquake insurance policy or endorsement. However, given the very low risk, the cost may not be worth it for most homeowners. The FEMA Earthquake Safety page notes that earthquake insurance is most important in high-risk areas. Still, it's wise to review your policy and understand what is covered.

How to Prepare Your Home for an Earthquake

Even in a low-risk state like South Dakota, basic preparedness can reduce injury and damage. The following steps are recommended by Ready.gov and FEMA:

• Secure heavy furniture and appliances: Anchor bookcases, televisions, and cabinets to wall studs. Use straps or brackets to secure water heaters, refrigerators, and other large appliances.
• Brace and reinforce: If you have a home with unreinforced masonry, consider consulting a structural engineer about retrofitting. This can include bolting the house to its foundation and bracing cripple walls.
• Protect your water heater: Strap your water heater to wall studs and install flexible gas connectors if you have natural gas. This prevents fires and water damage.
• Install latches on cabinets: Use childproof latches or earthquake latches to keep cabinet doors closed during shaking, preventing items from falling out.
• Secure breakables: Use museum putty or earthquake gel to hold items on shelves. Store heavy items on lower shelves.
• Create an emergency kit: Include water, non-perishable food, flashlight, batteries, first-aid supplies, medications, and a battery-powered radio. Ready.gov has a full list.
• Make a family plan: Decide how you will communicate and where you will meet if separated. Practice 'Drop, Cover, and Hold On' drills.
• Know how to shut off utilities: Learn how to turn off gas, water, and electricity in case of damage. Only shut off gas if you smell or hear a leak.

These steps are relatively inexpensive and can also help with other hazards like severe storms. For more detailed guidance, visit the South Dakota Office of Emergency Management website.

Frequently Asked Questions

Are earthquakes common in South Dakota?

No, earthquakes are not common in South Dakota. The state experiences very few felt earthquakes, and major damaging earthquakes have not occurred in recorded history. The USGS rates the seismic hazard as low, but small, barely noticeable tremors can occasionally happen. The risk is considered level 1 out of 5.

What should I do during an earthquake in South Dakota?

If you feel shaking, Drop, Cover, and Hold On. Drop to your hands and knees, cover your head and neck with your arms, and hold on to sturdy furniture. If you are indoors, stay there until shaking stops. If outdoors, move away from buildings, streetlights, and utility wires. Ready.gov provides detailed guidance for different situations.

Is earthquake insurance worth it in South Dakota?

For most homeowners in South Dakota, earthquake insurance is not typically necessary because the risk of damaging earthquakes is very low. Standard homeowner's policies do not cover earthquake damage, but given the low likelihood, many residents choose not to purchase additional coverage. However, if you live near a minor fault or have a vulnerable home, you may want to discuss options with your insurance agent.

Official Resources

• South Dakota Office of Emergency Management
• USGS Earthquake Hazards Program
• Ready.gov – Earthquakes
• FEMA Earthquake Safety