Fracking Quake: Allegheny Township Seismic Event Deemed Minor

The Pennsylvania Department of Environmental Protection cleared the EQT Porter well pad in Allegheny Township to resume full operations following a minor seismic event in October. State inspectors concluded that no violation occurred and that the site could remain active after reviewing the data.

On Oct. 4, at approximately 5 a.m., seismometers recorded a magnitude 0.5 earthquake near Willowbrook Road. The tremor was too small for residents to feel, but its proximity to an active fracking site triggered a state investigation. Regulators sought to determine if the event was induced by drilling or a natural tectonic shift.

Rob Skoumal, a research geophysicist with the U.S. Geological Survey, noted that induced earthquakes are rare in the region. He stated that among the 8,000 wells fractured in Pennsylvania, only about four have been linked to seismic activity. Skoumal explained that most fracking in the state targets the Marcellus shale, which he said is not associated with induced quakes. The Porter site, however, targets the deeper Utica shale.

The Utica shale extends up to 14,000 feet below the surface, which is 4,000 to 6,000 feet deeper than the Marcellus formation. Drilling this layer increases rock permeability but carries a higher risk of hitting pre-existing faults in the Precambrian basement rock. Skoumal said that fracturing rock naturally induces tiny, imperceptible tremors. The concern arises when drilling intersects an old fault line, potentially creating a quake large enough to register on the Richter scale.

State seismologist Kyle Homman described the regulatory response using a traffic light system. Events of magnitude 0.5 to 1.5 are considered green lights, allowing operators to continue business as usual. A yellow light, around magnitude 2.0, prompts state officials to discuss slowing fluid injection with the operator. A red light, defined as magnitude 3.0 or higher, typically results in a temporary shutdown of the well.

The Oct. 4 event fell into the green light category. Homman noted that the state has only known of one shutdown in the last decade due to a seismic event. In 2016, Hilcorp Energy voluntarily closed its North Beaver well pad in Lawrence County after a magnitude 1.9 tremor. DEP press secretary Neil Shader said the investigation into the Allegheny Township event was not conclusive regarding the specific cause of the activity.

EQT, the owner of the Porter Well Pad, did not respond to a request for comment. The state’s inspection report confirmed that the site met operational standards and required no further action.