Earthquake Risk by State: USGS Data Shows Where the Next Big One Could Strike

When Americans think about earthquake risk, they think about California. This is understandable — the San Andreas Fault is the most famous tectonic boundary in the country, and California has produced most of the destructive US earthquakes in living memory. But the USGS National Seismic Hazard Model (NSHM), updated in 2023, identifies significant earthquake hazard in 42 of 50 states.

Here is what the data shows, state by state, for the regions that matter most to property underwriters and catastrophe modelers.

California: The San Andreas and Hayward Faults

California's earthquake hazard is driven by two fault systems. The San Andreas Fault runs approximately 800 miles from the Salton Sea to Cape Mendocino and is capable of producing magnitude 8.0+ events. The most recent major rupture was the 1906 San Francisco earthquake (M7.9), which killed over 3,000 people and destroyed 80% of the city.

The Hayward Fault, running through the densely populated East Bay (Oakland, Berkeley, Fremont), is considered by the USGS to be the single most dangerous fault in the United States based on the combination of probability and exposure. The 2014 UCERF3 model estimated a 33% probability of a M6.7+ event on the Hayward Fault within 30 years. The Hayward Fault last ruptured in 1868 and is considered overdue for a major event.

The USGS NSHM 2023 estimates that the probability of at least one M6.7+ earthquake in California within the next 30 years exceeds 99%. For M7.5+, the probability is approximately 46%. These are not speculative numbers — they are derived from fault slip rate measurements, paleoseismic trench studies, and geodetic monitoring.

Pacific Northwest: The Cascadia Subduction Zone

The Cascadia Subduction Zone extends approximately 700 miles from northern California to British Columbia, where the Juan de Fuca plate is subducting beneath the North American plate. This fault is capable of producing M9.0+ megathrust earthquakes — comparable to the 2011 Tohoku earthquake in Japan.

The last full Cascadia rupture occurred on January 26, 1700, producing an estimated M9.0 earthquake and a tsunami that struck the coast of Japan (documented in Japanese historical records). Turbidite studies in marine sediment cores show that full-margin Cascadia events occur approximately every 200–600 years, with a mean recurrence interval of approximately 240 years.

As of 2026, 326 years have elapsed since the last full rupture. The USGS estimates a 7–15% probability of a M9.0+ Cascadia event within 50 years, and approximately 37% probability of a M8.0+ event. Oregon and Washington have significant population and infrastructure exposure in the Cascadia hazard zone, with Portland, Seattle, and the I-5 corridor all within the strong shaking footprint.

For cat modelers, Cascadia is a tail-risk scenario that produces industry losses in the $100B+ range — comparable to or exceeding Hurricane Katrina. The insured loss potential makes it one of the top three natural catastrophe scenarios for the US insurance market.

Central US: The New Madrid Seismic Zone

The New Madrid Seismic Zone (NMSZ), located at the junction of Missouri, Tennessee, Arkansas, Kentucky, and Illinois, produced the largest earthquake sequence in the recorded history of the contiguous United States: three events exceeding M7.0 between December 1811 and February 1812. These earthquakes were felt across the entire eastern US, rang church bells in Boston, and caused the Mississippi River to flow backwards temporarily.

The USGS estimates a 25–40% probability of a M6.0+ event in the NMSZ within 50 years, and a 7–10% probability of M7.0+. While these magnitudes are lower than Cascadia, the hazard is amplified by three factors:

Attenuation: Seismic waves attenuate (lose energy) much more slowly in the stable continental crust of the Central US than in the fractured crust of California. A M7.0 in the NMSZ produces damaging ground motion across a geographic area approximately 10 times larger than the same magnitude event in California.

Building stock: Structures in the NMSZ region are overwhelmingly unreinforced masonry — the most earthquake-vulnerable construction type. Memphis, the largest city in the zone, has extensive pre-code masonry construction. FEMA Hazus damage functions assign mean damage ratios of 40–60% for unreinforced masonry at MMI VIII.

Insurance penetration: Earthquake insurance take-up rates in the NMSZ states are below 5% of residential properties. A damaging event would produce enormous uninsured losses.

Oklahoma: Induced Seismicity

Oklahoma experienced a dramatic increase in earthquake activity between 2009 and 2016, driven by wastewater injection from oil and gas operations. The state went from averaging fewer than 2 M3.0+ events per year before 2009 to over 900 in 2015. The 2016 Pawnee earthquake (M5.8) was the largest instrumentally recorded earthquake in Oklahoma history.

Regulatory changes to injection volumes have reduced activity significantly since the 2015 peak, but Oklahoma continues to experience elevated seismicity. The USGS NSHM 2023 incorporates induced seismicity in its hazard maps for the first time, assigning meaningful hazard values to areas of central and northern Oklahoma that had negligible hazard in previous editions.

South Carolina: The Charleston Seismic Zone

The 1886 Charleston earthquake (estimated M7.0) remains the most destructive earthquake in the history of the US East Coast. The event killed approximately 60 people, destroyed 2,000 buildings, and caused damage equivalent to approximately $6 billion in 2026 dollars. MMI X shaking was recorded in the epicentral area.

The Charleston seismic zone shows continued microseismic activity. The USGS assigns Charleston a seismic hazard level comparable to some areas of California for long return periods (2,500 years). The combination of infrequent but large events, unreinforced masonry construction, and near-zero earthquake insurance penetration makes Charleston a significant tail-risk scenario.

Alaska and Hawaii

Alaska is the most seismically active US state by event count. The 1964 Great Alaska earthquake (M9.2) remains the second-largest instrumentally recorded earthquake globally. Alaska experiences M7.0+ events approximately every 1–2 years, though most occur in sparsely populated areas. The Anchorage metropolitan area has significant hazard from both megathrust events on the Alaska-Aleutian subduction zone and crustal faults.

Hawaii's volcanic seismicity is distinct from tectonic earthquakes but produces damaging events. The 2018 Kilauea eruption sequence included a M6.9 earthquake on the south flank of the island of Hawaii. The USGS NSHM includes Hawaiian seismic sources with hazard levels that exceed many mainland states.

How CivilSense Scores Earthquake Hazard

CivilSense computes earthquake hazard scores using three components weighted by their contribution to hazard at each location: historical seismicity from the USGS earthquake catalog (Gutenberg-Richter frequency analysis within 200km), proximity to mapped Quaternary faults from the USGS fault database, and NSHM probabilistic ground motion values at the 2% in 50-year exceedance level.

Each component is fully transparent. The score for any US address shows the contributing factors, the data sources, and the methodology. For the Pacific Northwest, the Cascadia subduction zone contribution dominates. For Central US locations, the NMSZ source governs. For California, fault proximity and historical frequency combine to produce the highest scores in the nation.

Enter any US address to see your earthquake hazard score with full methodology exposure — the same data a catastrophe modeler would use to evaluate your location.