On August 23, 2011, a 5.8 magnitude earthquake, centred in Virginia, shook Philadelphia. While there are no current earthquake reports for Philadelphia today, the 2011 event highlights the city’s seismic vulnerability.
The earthquake, felt as far as Florida and Ontario, caused minor damage in Philadelphia, mostly limited to rattled nerves and spilled drinks. A window at the Independence Blue Cross building shattered, and a vacant home partially collapsed in Camden, New Jersey, across the Delaware River. Despite the widespread tremors, there were no reported deaths and only minor injuries.
The epicentre of the earthquake was located in Louisa County, Virginia. The seismic waves rippled outwards, causing noticeable shaking in Philadelphia and prompting evacuations from high-rise buildings like the Comcast Center.
Comcast Center in Philadelphia.
Working on the 17th floor of the Comcast Center at the time, firsthand accounts described the initial shaking as subtle, but quickly recognised as an earthquake due to reports emerging from Washington, D.C., on social media. The swaying motion of the water in a rooftop pool across from the Comcast Center provided visual confirmation of the tremor’s impact.
Following the initial shaking, an announcement over the building’s loudspeaker system advised employees to remain calm, stating that there was no structural damage. However, a subsequent announcement, delivered with a more panicked tone, contradicted the earlier message and created a sense of unease among the building’s occupants.
The conflicting information led to confusion and fear, prompting many employees to evacuate the building despite the initial assurances of safety. Eventually, a calmer voice announced the closure of the Comcast offices for the day, leading to a mass exodus from the building.
While the earthquake caused minimal physical damage in Philadelphia, it left a lasting impression on those who experienced it. The event highlighted the city’s susceptibility to earthquakes and served as a reminder of the importance of preparedness. Although the Washington Monument sustained damage requiring closure for several years, the Philadelphia earthquake of 2011 is largely remembered as a surprising, but ultimately harmless, event.