Earthquake Risk in the US: How FEMA Scores It and How to Prepare

Written by Dvir · Data: FEMA National Risk Index v1.20 · Updated August 4, 2026

Earthquakes are the National Risk Index’s second-largest hazard by expected loss — roughly $26 billion per year nationally — despite being rare. That combination is exactly what makes them tricky to think about: a county can go a century without a damaging quake and still carry enormous risk, because when the ground finally moves under a modern city, losses arrive all at once and uninsured. The 1994 Northridge earthquake, a magnitude 6.7 under suburban Los Angeles, caused over $20 billion in damage in about twenty seconds.

What counts as earthquake risk

The NRI’s earthquake hazard (code ERQK) covers ground shaking from fault rupture — the primary killer of buildings — along with the liquefaction and ground failure that shaking triggers. (Earthquake-caused tsunamis and landslides are booked under their own NRI hazards.)

US earthquake risk is not just the San Andreas. The Cascadia Subduction Zone off Oregon and Washington can produce magnitude-9 events — the last one, in January 1700, dropped the coastline and sent a tsunami to Japan. The New Madrid Seismic Zone produced some of the strongest quakes in US history (1811–12) under what is now Missouri, Tennessee, and Arkansas. Salt Lake City sits on the Wasatch Fault; Charleston, SC was devastated in 1886; Alaska has more large quakes than the rest of the country combined; and Hawaii, Puerto Rico (2020), and even Oklahoma (induced seismicity) round out the map.

How the NRI measures it

FEMA combines each county’s exposure (building value and population), annualized earthquake frequency derived from USGS National Seismic Hazard Model probabilities, and historic loss ratios into an Expected Annual Loss, scored 0–100 relative to all counties. For a hazard this rare, the “annualized” framing matters: a county expecting one severe quake per 200 years with $200B exposed can carry a $1B-class EAL even if nobody alive has felt a big one there.

Where the risk concentrates

3,137 counties record measurable earthquake risk, but the top is emphatic: Los Angeles County, CA leads the nation (score 100, ~$4.6 billion expected annual loss — the largest single county-hazard number in the entire index outside flooding). The Bay Area follows — Alameda (~$1.35B) and Santa Clara (~$1.19B) counties — with Orange County, CA and King County, WA (Seattle, ~$1.2B) completing the top five. High ratings continue through the Puget Sound, Portland, Salt Lake City’s Wasatch Front, Memphis and the New Madrid zone, Charleston, Anchorage, and Honolulu.

How to read your county’s score

Earthquake risk is about when your buildings were built as much as where they stand. Modern seismic codes (roughly post-1994 in the West) perform well; the dangerous stock is older: unreinforced masonry, pre-1980 concrete, “soft-story” apartments over open parking, and houses not bolted to their foundations. If your county rates High or Very High, the questions are: What vintage is your home? Is it bolted and braced? Does your city have a mandatory retrofit program (LA, San Francisco, and Seattle do)? And crucially — do you have earthquake insurance? Standard homeowners policies exclude earthquake entirely; in California only about 10–15% of homeowners carry it.

What actually reduces the risk

  • Bolt and brace. For wood-frame houses, a foundation bolt-and-cripple-wall-brace retrofit costs a few thousand dollars, prevents the most common catastrophic failure (sliding off the foundation), and is subsidized in California (Earthquake Brace + Bolt).
  • Kill the soft story. Living above open parking or storefronts in an older building is the highest-risk residential situation; retrofits add steel frames or shear walls.
  • Secure the interior. Strap the water heater (fire + water loss), anchor tall furniture and TVs, use museum putty and cabinet latches. Most injuries are from falling objects, not collapsing buildings.
  • Drop, Cover, Hold On — under a table, not in a doorway, and do not run outside during shaking; facades kill. Practice via the annual Great ShakeOut.
  • Get early warning. The ShakeAlert system delivers seconds of warning via the MyShake app and wireless alerts in CA, OR, and WA — enough to drop, stop surgery, or slow a train.
  • Prepare for two weeks on your own. A Cascadia or San Andreas event will overwhelm response capacity; water (1 gal/person/day), a gas shutoff wrench, and out-of-state contact plans are the standard kit.

The earthquakes that wrote the building code

Every major provision of American seismic design traces to a specific failure.

San Francisco (1906). A magnitude ~7.9 rupture on the San Andreas destroyed most of the city — largely through the fire that followed, after the water mains broke. It established two enduring lessons: earthquakes are fire events, and lifelines fail together.

Long Beach (1933). A moderate magnitude-6.4 quake collapsed dozens of school buildings. It happened after school hours, which is the only reason it is not remembered as a massacre of children. California’s legislature passed the Field Act within a month, imposing state engineering oversight on school construction — the first serious seismic building law in the country.

Alaska (1964). The magnitude 9.2 Good Friday earthquake, the largest ever recorded in North America, produced ground failure, landslides, and a destructive tsunami. It drove the creation of the modern federal earthquake research effort and much of what is known about subduction-zone behavior.

San Fernando (1971). Freeway overpasses collapsed, a hospital failed, and a dam nearly did. The result was a wholesale revision of bridge and hospital design standards and the beginning of California’s long-running seismic retrofit programs for public infrastructure.

Loma Prieta (1989) and Northridge (1994). Loma Prieta collapsed a double-deck freeway and a section of the Bay Bridge and showed what soft soils do to shaking. Northridge, a magnitude 6.7 directly under a dense suburb, caused over $20 billion in damage in seconds, destroyed apartment buildings with open parking on the ground floor, and revealed that welded steel moment-frame connections — believed to be the safest system in use — were cracking. The soft-story retrofit ordinances now in force in Los Angeles, San Francisco, and other cities exist because of Northridge, and steel connection design was rewritten nationwide.

Nisqually (2001) in Puget Sound and the Puerto Rico sequence (2019–2020) both hit regions with large stocks of unreinforced masonry and non-ductile concrete, and both produced retrofit programs that are still incomplete.

Where and when: the seismic geography of the US

Earthquakes have no season. What they have is a geography of recurrence intervals, and the intervals are long enough that human memory is a terrible guide to risk.

  • California. The San Andreas system plus dozens of active faults beneath the Los Angeles and Bay Area basins. Frequent moderate events; the largest expected losses in the country because of what is built on top.
  • Pacific Northwest. The Cascadia Subduction Zone is capable of magnitude-9 ruptures lasting several minutes, with a tsunami following within 15–30 minutes on the outer coast. The last full rupture was January 1700. Seattle also has the shallow Seattle Fault directly beneath the city.
  • Intermountain West. The Wasatch Fault runs beneath Salt Lake City and the Utah population corridor. Idaho, Nevada, and Montana all have active normal faulting.
  • New Madrid Seismic Zone. The 1811–1812 sequence produced several of the largest earthquakes in the recorded history of the continent, in what is now Missouri, Tennessee, Arkansas, and Kentucky. Mid-continent geology transmits shaking far more efficiently than the fractured crust of the West, so a New Madrid event affects a much larger area than a Californian quake of the same magnitude — over a region built almost entirely without seismic detailing.
  • Charleston, South Carolina. The 1886 earthquake was strongly felt over most of the eastern US and remains the benchmark for East Coast seismic hazard.
  • Alaska and Hawaii. Alaska experiences more large earthquakes than the rest of the country combined; Hawaii’s are volcanic-tectonic and frequent.
  • Oklahoma and Kansas. A pronounced increase in felt earthquakes beginning around 2009 was linked by USGS research to deep wastewater injection from oil and gas operations. Rates fell substantially after injection was regulated, but this is the one place in the country where seismic hazard has been demonstrably human-modified in both directions.

Retrofits, ranked by value

Seismic mitigation has an unusually clear cost-benefit ordering, and the cheap items are near the top.

  • Strap the water heater. Under a hundred dollars of parts. An unstrapped heater topples, breaks the gas line, and starts a fire in a house you can no longer get water to. Do this first, everywhere in the West.
  • Anchor tall furniture, TVs, and heavy objects. Bookcases and dressers to studs, TVs with straps, latches on upper cabinets, museum putty under anything breakable on a high shelf. Most earthquake injuries are from falling objects, and this is a weekend and a hundred dollars.
  • Bolt the house to the foundation and brace the cripple walls. For pre-1980 wood-frame houses on a raised foundation, this is the single most important structural retrofit: it prevents the house sliding off its foundation, which is the classic total loss. Typical costs run a few thousand dollars, and California’s Earthquake Brace + Bolt program has offered substantial grants for exactly this work.
  • Fix the soft story. An apartment building or house with living space over open parking or a wide garage opening has no lateral resistance at its weakest level. Retrofits add steel moment frames or shear walls. Several cities now mandate it; if you own or rent in such a building, know its status.
  • Address unreinforced masonry. Brick buildings without steel reinforcement are the deadliest common structure type in earthquakes worldwide. Retrofit means anchoring walls to floors and diaphragms — expensive, but the alternative is collapse.
  • Flexible gas connectors and an accessible shutoff. Automatic seismic gas shutoff valves exist and are required in some jurisdictions. At minimum, keep a wrench attached to the meter and know how to use it.
  • Non-ductile concrete. Pre-1980 concrete frame buildings are the other high-fatality category. This is an owner and city-policy problem more than a homeowner one, but it should influence where you choose to live or work.

Earthquake insurance: the biggest coverage gap in America

Standard homeowners and renters policies exclude earthquake damage entirely. Not sub-limited — excluded. It has to be bought separately, and most people in high-hazard counties have not.

  • How to buy it. In California, through the California Earthquake Authority (sold via participating insurers) or a growing private market. Elsewhere, as an endorsement or a standalone policy.
  • Deductibles are percentage-based and large. Commonly 5–25% of the dwelling limit, applied separately to the structure and sometimes to contents. On a $600,000 rebuild limit, a 15% deductible is $90,000. This is why people say the coverage is for catastrophe, not for cracked drywall — and why choosing a lower deductible is worth pricing rather than assuming.
  • Fire following an earthquake is usually covered by the homeowners policy, since fire is a covered peril even when the earthquake that caused it is not. Shake damage is not.
  • Renters need contents coverage. An earthquake endorsement on a renters policy is inexpensive relative to replacing a household’s belongings.
  • Loss of use matters more here than almost anywhere. After a major urban earthquake, tens of thousands of units become uninhabitable at once and rents spike. Check the ALE limit.
  • Retrofit discounts exist. Bolted-and-braced homes qualify for premium reductions with several carriers and with the CEA. Keep the permit and inspection records.
  • The federal backstop is thin. Individual FEMA assistance after a declared disaster is capped and is designed to relieve hardship, not to rebuild a house. Assume it will not make you whole.

Before, during, and after

Before. Turn on ShakeAlert-powered warnings if you are in California, Oregon, or Washington — via the MyShake app, Android’s built-in earthquake alerts, and Wireless Emergency Alerts. They deliver seconds to tens of seconds of warning, which is enough to get under a table, stop an elevator, or pull a train’s brakes. Store water at one gallon per person per day for at least two weeks, not three days: a Cascadia or San Andreas event will sever roads, water mains, and fuel supply over a region far larger than any response capacity. Keep sturdy shoes and a flashlight tied to the bed frame — broken glass on the floor in the dark is the first hazard after shaking stops. Agree on an out-of-state contact, since long-distance texting often works when local calls do not.

During. Drop, Cover, and Hold On. Get under a sturdy table and hold on to it; if there is none, get down beside an interior wall away from windows and cover your head and neck. Do not stand in a doorway — that advice came from adobe construction and is wrong for modern buildings. Do not run outside during shaking, where falling facades, glass, and parapets kill people. If you are in bed, stay there and cover your head with a pillow. If you are driving, pull over clear of overpasses and power lines and stay in the vehicle. On the coast in Cascadia or Alaska, strong shaking that lasts a long time is your tsunami warning — as soon as it stops, walk inland and uphill immediately without waiting for an official alert.

After. Expect aftershocks, some of them damaging, for days to months. Check for gas leaks by smell and sound; shut off the gas only if you suspect a leak, because restoring service requires a utility visit that may take weeks. Do not use candles. Check on neighbors, particularly in older buildings. Photograph damage before cleanup, and get a structural assessment before re-entering a building with cracked masonry, a leaning frame, or a collapsed ground floor. If your house shifted on its foundation, that is a structural claim regardless of how intact the walls look.

Sources

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