Most Seismically Active Regions in the US

US States Ranked by Catalog Total (Live)

The table below ranks US states and territories by total earthquake count from the USGS Comprehensive Earthquake Catalog (ComCat) as ingested by PlainQuake (M4.0+, since 2005). Numbers render directly from our database, when the catalog updates, this page updates with it.

Source: USGS Comprehensive Earthquake Catalog (ComCat), ingested by PlainQuake (M4.0+, since 2005) USGS Comprehensive Earthquake Catalog (ComCat), ingested by PlainQuake (M4.0+, since 2005) Catalog counts update automatically as new USGS data is published. US state figures are aggregated from the same global M4+ ComCat record.

What the catalog tells us

Alaska accounts for roughly 52% of the total volume in the top-15 list above, illustrating its dominance over every other US state. Northern Mariana Islands and Guam, Pacific island territories, appear surprisingly high because of their proximity to the Mariana Trench subduction zone, despite low population. California's count, while modest in absolute terms within the catalog window, sits over a fault system that produces some of the highest-magnitude crustal earthquakes in the world (max M7.2 recorded in our catalog window; M7.9 in 1857 outside the window). The contrast between high-count low-magnitude regions (Hawaii volcanic flank) and low-count high-magnitude regions (the lower-48 historic events) is the central lesson of US seismic hazard.

Why Hawaii ranks below the Pacific territories

Hawaii's catalog volume is dominated by volcanic-flank events at Kilauea and Mauna Loa, small, high-frequency, and shallow. The Northern Mariana Islands and Guam, by contrast, sit at one of the deepest subduction zones on Earth and produce far more detected M4+ events than typically appreciated in U.S. discussions of seismic risk.

Oklahoma's induced-seismicity decade

Oklahoma's 2010-2016 swarm involved high-volume wastewater injection into Class II disposal wells, triggering thousands of M3+ events. After Oklahoma Corporation Commission directives in March 2016 cut injection volumes substantially, the rate fell within 18 months. The 2016 Pawnee event (Mw 5.8) remains the largest induced earthquake recorded in U.S. history.

How New Madrid and Charleston complicate the ranking

The contemporary catalog (2005-2025) does not capture the great historical events that define long-term U.S. hazard: the 1811-1812 New Madrid sequence (Missouri/Arkansas/Tennessee/Kentucky), estimated M7.5-8.0, and the 1886 Charleston M7.3 in South Carolina. Both regions are classified by USGS NSHM 2023 as significant hazard zones with multi-century recurrence intervals. Catalog rank alone, while useful as a relative measure, undersells long-term hazard in the central and eastern U.S.

Alaska: The Giant

Alaska's seismicity is in a category of its own. The Pacific Plate subducts beneath the North American Plate along the 4,000 km Aleutian Arc at a rate of about 56 mm per year, among the fastest convergence rates of any subduction zone on Earth. This produces a continuous stream of earthquakes at all magnitudes, including frequent M7+ events. Alaska averages more M7+ earthquakes than any other US state and has recorded two M8.5+ events since 1900 alone.

The 1964 Good Friday Earthquake (M9.2) remains the largest ever recorded in North America and the second-largest ever instrumentally recorded globally. It generated a Pacific-wide tsunami, caused massive landslides, and raised and subsided vast areas of coastline. The 2018 Anchorage earthquake (M7.1) caused extensive infrastructure damage in modern buildings designed to current codes, demonstrating that even well-prepared cities face significant impacts from major events. Explore Alaska earthquake data on PlainQuake.

California: The Most Continuously Active Lower-48 State

California's seismicity is driven by the San Andreas Fault System, a 1,300 km right-lateral transform boundary where the Pacific Plate moves northwest relative to the North American Plate at about 50 mm per year. The San Andreas itself and its numerous parallel and branching faults (Hayward, Calaveras, San Jacinto, Garlock, Elsinore) make it the most continuously active fault network in the lower 48.

The Hayward Fault, which runs beneath the heavily urbanized East Bay (Oakland, Berkeley, Fremont), is considered by many seismologists to be among the most dangerous urban faults in the world. The fault last ruptured fully in 1868 (M6.8) and has been building stress for over 150 years. The southern San Andreas (Los Angeles region) is considered overdue for a "Big One" - a M7.8+ rupture that would cause catastrophic damage across the Los Angeles basin. Review California earthquake data.

Pacific Northwest: Cascadia's Sleeping Giant

Oregon and Washington rank lower in annual earthquake frequency than California because the Cascadia Subduction Zone is currently in its "locked" phase, accumulating stress rather than releasing it in frequent smaller events. This makes the Pacific Northwest paradoxically more dangerous in the long run. When the Cascadia zone ruptures, as it has roughly every 200-500 years throughout geologic history, the event will be M8-9+ and will generate a Pacific Northwest tsunami within 15-20 minutes.

Oregon and Washington also have numerous shallow crustal faults capable of producing damaging M6-7 earthquakes. The Seattle Fault, which runs beneath Puget Sound and the greater Seattle metropolitan area, last ruptured approximately 1,100 years ago in a M7+ event that generated a local tsunami in Puget Sound. See Washington and Oregon earthquake data.

Intermountain West: Nevada, Utah, and the Basin and Range

The Basin and Range Province, stretching from eastern California across Nevada, Utah, Arizona, and New Mexico, is an actively extending region where the crust is being stretched apart. This extension creates numerous north-south oriented normal faults, producing significant seismic activity. Nevada ranks among the most active lower-48 states by earthquake frequency, with events recorded across its many active fault zones.

The Wasatch Front (Utah) is one of the most hazardous fault zones in the Mountain West. The Wasatch Fault runs along the base of the Wasatch Mountains directly beneath the heavily urbanized Salt Lake City-Provo-Ogden corridor, where over 80% of Utah's population lives. The Wasatch Fault has not produced a major rupture in historical times but has a documented history of M7+ earthquakes in the geologic record.

Yellowstone in Wyoming deserves special mention as a supervolcanic system that generates frequent shallow earthquakes from hydrothermal, magmatic, and tectonic sources. While a supervolcanic eruption is extraordinarily unlikely on human timescales, Yellowstone's seismicity and ground deformation are monitored continuously by USGS. See Wyoming earthquake data.

Central US: New Madrid and Induced Seismicity

The New Madrid Seismic Zone (NMSZ) in the central US represents a major hazard to a region largely unaware of seismic risk. The 1811-1812 New Madrid earthquake sequence, three events estimated at M7.5-8.0, occurred along an ancient failed rift beneath the Mississippi Embayment. These earthquakes caused ground liquefaction across vast areas, altered river channels, and were felt throughout most of the eastern US.

Unlike western states where seismic risk is broadly recognized, many Midwestern communities have aging building stock constructed without seismic design requirements. A repeat of the 1811-1812 sequence would be far more damaging today than at its historic occurrence. Explore Tennessee and Missouri earthquake data, both of which sit near the NMSZ epicenter zone.

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