Damaging earthquakes that rocked West Texas in recent days were likely caused by oil and gas activity in an area that has weathered tremors for decades, according to the U.S. Geological Survey.

A sequence that began in 2021 erupted with its largest quake on Friday, a magnitude 5.1 in the most active area in the country for quakes induced by oil and gas activities, experts say. The recent quakes damaged homes, infrastructure, utility lines, and other property, weakening foundations and cracking walls, the city of Snyder Office of Emergency Management said on Facebook. Officials declared a disaster in Scurry County.

There have been more than 50 earthquakes with a magnitude of 3 or larger — the smallest quakes generally felt by people are magnitude 2.5 to 3 — in the yearslong sequence, said Robert Skoumal, a research geophysicist with the USGS, in an email. A sequence is generally a swarm of earthquakes in a particular region motivated by the same activities, he said.

While Friday’s was the largest in the sequence, officials have also recorded a recent 4.5, a 4.9 on July 23 and a 4.7 last year.

“This particular portion of the Permian Basin has a long history of earthquakes induced by oil and gas operations, going back to at least the 1970s,” said Skoumal.

The Permian Basin, which stretches from southeastern New Mexico and covers most of West Texas, is a large basin known for its rich deposits of petroleum, natural gas and potassium and is composed of more than 7,000 fields in West Texas. It is the most active area of induced earthquakes in the country and likely the world, according to the USGS. The are many ways people can cause, or induce, earthquakes, but the vast majority of induced earthquakes in the Central United States are caused by oil and gas operations, Skoumal said.

Earthquakes were first introduced to the area via water flooding, a process in which water is injected into the ground to increase production from oil reservoirs.

Four other tremors larger than a magnitude 5 have rattled western Texas in the past few years. The biggest was a 5.4. “All four of these earthquakes were induced by wastewater disposal,” said Skoumal.

Further analysis is needed to confirm the specific cause of the region’s earthquakes, but because the area isn’t naturally seismic and has a long history of induced earthquakes, “these recent earthquakes are likely to also have been induced by oil and gas operations,” said Skoumal.

Oklahoma experienced a dramatic spike in the number of earthquakes in the early 2010s that researchers linked to wastewater from oil and gas extraction that was being injected deep into the ground, activating ancient faults deep within the earth’s crust. The wastewater is left over from oil and natural gas production and includes saltwater, drilling fluids and other mineralized water.

The large increase in Oklahoma quakes more than a decade ago led state regulators to place restrictions on the disposal of wastewater, particularly in areas around the epicenter of quakes. Since then, the number of quakes began to decline dramatically.

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AP writer Sean Murphy contributed from Oklahoma City.

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