The Counties With The Most Earthquakes

Alaska records more large earthquakes than the other 49 states combined, and the interior census area that leads this list is slightly larger than the state of Montana. One terminology note first: Alaska has no counties, so this list uses the Census Bureau's broader county-equivalent category, which includes the state's boroughs and census areas as well as true counties elsewhere. The five entries below include a subduction-adjacent Alaskan expanse with about 5,300 residents, a volcanic island county where seismometers follow magma rather than faults, and a rural Oklahoma county that began shaking in step with wastewater disposal wells. Event counts here come from USGS and state seismic network catalogs, which log far more earthquakes than anyone on the surface ever feels.

Yukon-Koyukuk Census Area, Alaska

At roughly 147,800 square miles, this is the largest county-equivalent in the United States, slightly larger than the state of Montana, and it encompasses a range of landscapes, including mountains, forests, and tundra. The 2020 census counted 5,343 residents spread across its entire area. Statewide, Alaska accounts for roughly half of all earthquakes recorded in the United States, and the Alaska-Aleutian subduction zone that produces the largest of them sits far to the south, where the Pacific Plate is forced beneath the North American Plate. Interior seismicity, which is what Yukon-Koyukuk actually experiences, works differently. Crustal deformation transmitted inland from that plate boundary is taken up by right-lateral strike-slip faults such as the Denali, Tintina, and Kaltag systems, and by a set of narrow north-northeast-trending seismic zones near Rampart, Minto, and Dall City.

Thousands of earthquakes occur across the region every year, most of them microscopic tremors detectable only by seismometers, but the interior is capable of much more. A magnitude 7.1 earthquake struck near Rampart in 1968, one of the largest instrumentally recorded events in interior Alaska. This extraordinary earthquake count comes with a geographic caveat: there are very few people in the areas where most earthquakes occur. A deep tremor can register clearly on a seismic network and still leave no trace on the surface. The United States Geological Survey (USGS), the Alaska Earthquake Center, and other organizations consistently monitor this activity, making the census area a striking example of how a region can be extremely active underground without being known for the damage commonly associated with these natural occurrences.

Hawaii County, Hawaii

For Hawaii's Big Island, earthquakes tend to be part of a much larger geological process. Hawaii County encompasses the entire island and spans approximately 4,000 square miles of land, with roughly 200,000 residents at the 2020 census, along with thousands of tourists and travelers who regularly visit. Beneath the surface, volcanic forces constantly reshape the landscape, and the earthquakes serve as cues as to what is happening underground. The long-term USGS Hawaiian Volcano Observatory catalog reports a statewide average of about 100 earthquakes of magnitude 3.0 or greater per year, along with roughly 10 at magnitude 4.0 or greater and about 1 at magnitude 5.0 or greater. Those figures rise sharply during volcanic unrest; the 2018 lower East Rift Zone eruption alone pushed the decade of 2009 through 2018 to nearly 4,800 magnitude 3.0 events.

The main volcanoes behind the activity are Kilauea and Mauna Loa, and unrest often produces swarms of small earthquakes across the island. Unlike most of Alaska's seismic activity, Hawaii's earthquakes are more commonly associated with volcanism. As magma moves through the crust, it changes pressure, fractures surrounding rock, and forces existing structures to shift. That makes earthquake activity a crucial part of monitoring Hawaii's volcanoes. The Hawaiian Volcano Observatory continuously tracks these changes, and Hawaii County experiences the majority of the state's tremors because of its size, location, and the geological factors described above. Here, seismic activity is more than a tally of ground shaking; it can serve as a time-sensitive measure to warn and protect residents ahead of an eruption.

Kern County, California

Few dates demonstrate this county's seismic significance more clearly than July 21, 1952. Early that morning, at 4:52 a.m., a magnitude 7.3 earthquake, still cited as 7.5 in many older accounts, ruptured the White Wolf Fault near Wheeler Ridge, about 23 miles south of Bakersfield, and produced violent shaking across a broad stretch of Southern California. Damage reached about $60 million, or roughly $700 million in today's dollars. Buildings crumbled, railway tunnels shifted, and 12 people lost their lives, nine of them in Tehachapi, which suffered the worst of it. This was the largest earthquake in the contiguous United States since the San Francisco earthquake of 1906, and its aftershock sequence persisted through July and into August, the strongest being a magnitude 5.8 event on August 22 that killed two more people in Bakersfield.

That legacy is part of a much larger pattern. Kern County lies in a particularly complex region of California where several major faults intersect, creating numerous pathways through which tectonic stress can accumulate and eventually be released. The San Andreas Fault, the Garlock Fault, the White Wolf Fault, and the western edge of the Eastern California Shear Zone all contribute to the fractured crust and shifting blocks beneath the county. This geological complexity makes Kern County a recurring hotspot for earthquake sequences.

The most recent demonstration came in July 2019, when a magnitude 6.4 foreshock on July 4 was followed 34 hours later by a magnitude 7.1 mainshock near Ridgecrest, in the county's eastern desert. The sequence ruptured previously unmapped faults, generated more than 14,000 aftershocks within 11 days, and was felt as far away as Phoenix. Monitoring by the USGS and Caltech through the Southern California Seismic Network gives scientists an increasingly detailed view of that activity and its drivers.

Lincoln County, Oklahoma

Lincoln County is a rural stretch of central Oklahoma, covering roughly 960 square miles and with about 35,000 residents at the 2020 census. It became part of an extraordinary seismic transformation during the height of the state's oil and gas boom. Following that period, the county recorded a sharp increase in earthquakes of magnitude 3.0 or greater, and in the mid-2010s, Oklahoma as a whole logged more such events in a year than California did.

Scientists have linked this to human-induced changes in the underground environment. Wastewater produced by oil and gas extraction requires disposal, which operators handle by injecting it into deep geological formations, chiefly the Arbuckle Formation in this part of the state. Under specific circumstances, the added fluid raises pressure within the subsurface, and when that pressure reaches an existing fault, it reduces the friction holding the fault in place, allowing the rock to slip. The resulting phenomenon, known as induced seismicity, has made parts of Oklahoma, including Lincoln County, among the most closely studied human-induced earthquake zones in the United States.

The clearest local example arrived on November 6, 2011, when a magnitude 5.7 earthquake struck near Prague along the Wilzetta fault. It destroyed 14 homes, buckled a section of US Highway 62, injured two people, and was felt more than 800 miles away. It stood as the strongest earthquake ever recorded in Oklahoma until a magnitude 5.8 event near Pawnee in 2016, and a magnitude 5.1 earthquake hit almost the same spot in February 2024. The surge eventually prompted the Oklahoma Corporation Commission, the state agency that regulates oil and gas, to restrict wastewater injection, shutting some disposal wells and limiting volumes in areas of particular concern. The USGS induced seismicity program and the Oklahoma Geological Survey continue to study the relationship.

Los Angeles County, California

About 10 million people live across the 4,751-square-mile Los Angeles County, on a landscape of freeways, housing, skyscrapers, and industrial infrastructure. All of it sits above one of the most complex seismic environments in the country. The Southern California Seismic Network catalogs on the order of 20,000 earthquakes a year across the wider region, and almost none of them register on the public radar. The exceptions are consequential. The 1971 San Fernando and 1994 Northridge earthquakes, at magnitudes 6.6 and 6.7, respectively, demonstrated the destructive potential here; Northridge alone caused tens of billions of dollars in damage and 57 deaths.

Los Angeles County does not sit on a single fault. Tectonic stress generated by the movement of the North American and Pacific plates is distributed across a dense network of faults, including concealed blind thrust systems such as the Puente Hills fault, which provide another mechanism for crustal movement. The ground itself matters too. Much of the Los Angeles metropolitan area sits on deep sedimentary basins, and those layers of softer material can prolong and amplify seismic waves, intensifying the shaking produced by an earthquake.

The combination of geology, population density, and location makes Los Angeles County fundamentally different from the other hotspots here. A small earthquake in interior Alaska might go entirely unnoticed, while a rupture beneath Los Angeles County would occur amid one of the largest concentrations of infrastructure and people in the United States. Caltech, the USGS, and the California Integrated Seismic Network monitor the area and track even the smallest events, because a few seconds of intense shaking can cost millions of dollars.

Where America's Ground Moves Most

A raw earthquake count measures instrument coverage nearly as much as it measures geology, which is why interior Alaska can log thousands of events a year that almost nobody reports feeling. Kern County's record is written into a single morning in 1952 and into the Ridgecrest sequence 67 years later, while Los Angeles County's is written into the sedimentary basin beneath Northridge, where soft ground turned a magnitude 6.7 rupture into one of the costliest disasters in American history. Lincoln County makes the opposite point: that a county with no significant seismic history can be pushed into one within a decade by what is injected beneath it. Across these five county equivalents, frequency, severity, and consequence align differently in every case, which is why seismologists rarely rank them on a single number.