Exploration of the Tewksbury Earthquake: Unraveling the Mystery Behind Varied Shaking Reports

On April 5, 2024, a 4.8 magnitude earthquake struck Tewksbury, New Jersey, surprising millions on the East Coast as far away as New York City who reported strong shaking. Surprisingly, damage near the epicenter was minimal, prompting researchers to investigate the earthquake’s rupture direction. Their analysis suggested that the rupture’s pathway may have altered the intensity of shaking experienced in various locations, highlighting the need for comprehensive studies of seismic activity in the region.

The recent Tewksbury earthquake, which registered a magnitude of 4.8 on April 5, 2024, not only startled millions across the U.S. East Coast but also raised questions regarding the unusual patterns of reported shaking. This earthquake stands as the largest recorded in New Jersey since 1900, yet surprisingly, minimal damage was reported near its epicenter while strong shaking was felt 40 miles away in New York City. In light of these observations, researchers led by YoungHee Kim from Seoul National University published an analysis in The Seismic Record, shedding light on the earthquake’s rupture direction and its implications on the intensity of shaking experienced. Kim and her colleague, Won-Young Kim of the Lamont-Doherty Earth Observatory, ventured to the epicenter shortly after the quake, expecting to observe significant structural damage. Surprisingly, their findings contradicted expectations; there were no visible damages or distress among individuals in proximity to the epicenter, who appeared to respond calmly to the seismic event. This observation sharply contrasted with the large volume of reports from New York City residents, approximately 65 kilometers away, who described intense shaking. This earthquake yielded over 180,000 felt reports, a record high for the U.S. Geological Survey’s “Did You Feel It?” platform, with an estimated 42 million individuals sensing the tremors from Virginia to Maine. Reports indicated disparate shaking intensities, with areas southwest of the epicenter experiencing weak shaking, while those to the northeast encountered light to moderate shaking. According to models for the eastern U.S., a magnitude 4.8 quake typically generates very strong shaking within a 10-kilometer (about 6 miles) radius of its epicenter. Thus, Kim and her team investigated the earthquake’s rupture direction more closely. Utilizing seismic waves known as Lg waves, which are specific to crustal movements, the researchers were able to model the earthquake’s rupture dynamics despite the lack of dense seismic monitoring stations nearby. Their findings revealed that the rupture advanced towards the east-northeast along a fault plane that dips eastwards. This mechanism may have resulted in the funneling of seismic waves away from the epicenter towards regions further northeast, where stronger shaking was reported. Unlike typical earthquakes in the northeastern United States, which usually occur along north-south trending faults, the Tewksbury earthquake displayed a combination of thrust and strike-slip faulting along a potential north-northeast trending fault. Following the quake, minor damage was documented, particularly the partial collapse of the façade of Taylor’s Mill, a historical structure in Lebanon, New Jersey. Despite not being able to definitively link the earthquake to a known fault, Kim and her colleagues hypothesized the presence of an uncharted fault plane, supported by the numerous aftershocks that followed. Boyd and his team emphasized the importance of ongoing studies to identify new earthquake sources and enhance understanding of stress distribution in eastern regions. Seismometers deployed by the U.S. Geological Survey (USGS) are expected to remain operational for at least five months, facilitating further investigations into the earthquake’s mechanics and the region’s seismic behavior.

The Tewksbury earthquake of April 2024 marks a significant seismic event in New Jersey’s history as the largest earthquake recorded in the state since 1900. This earthquake not only surprised those in its immediate vicinity but also caused sensations of shaking as far as New York City, bringing attention to the geological features underlying the eastern United States. Understanding why reports of shaking varied dramatically in intensity from the epicenter to distant urban areas requires a deeper investigation into the nature of the earthquake’s rupture and its interaction with local geological structures. Researchers utilized advanced modeling techniques to analyze seismic waves generated by the earthquake, seeking to explain the apparent discrepancy between the shaking reported by residents and the minimal damage observed nearby. Exploring fault mechanisms common in the northeastern U.S. also provided insight into how this earthquake deviates from typical patterns, suggesting anomalies in tectonic activity that may warrant further study.

The Tewksbury earthquake has brought to light several intriguing phenomena concerning seismic activity in the northeastern United States, particularly regarding how rupture direction can significantly influence perceptions of shaking intensity. The findings from this event suggest a need for enhanced monitoring of lesser-known faults and emphasize the complexities of seismic behaviors in regions historically considered less seismically active. As ongoing studies are conducted, this research not only augments our understanding of earthquake mechanisms but also aids in the preparation for potential future seismic hazards in the region.

Original Source: phys.org