On April 5, 2024, a magnitude 4.8 earthquake struck Tewksbury, New Jersey. While the tremor caused minimal damage near its epicenter, an unexpected number of people in New York City—nearly 40 miles away—reported feeling strong shaking.
This raised significant questions about the nature of the earthquake and its seismic behavior. Researchers now believe that the earthquake’s rupture direction, along with the behavior of seismic waves, played a crucial role in why such a wide area experienced intense shaking.
- The Unusual Shaking Phenomenon
- The Science Behind the Earthquake’s Reach
- How Seismic Waves Played a Role
- The Role of Fault Systems in Earthquakes
- Implications for Seismic Hazard Assessment
- Conclusion
- People May Ask
- Why was the earthquake felt so far from the epicenter?
- Did the earthquake cause significant damage?
- How many people felt the earthquake?
- What makes the Tewksbury earthquake different from other earthquakes in the region?
- What did researchers discover about fault systems in the area?
The Unusual Shaking Phenomenon
The Tewksbury earthquake, although moderate in magnitude, had an unusually broad impact. Over 180,000 people reported feeling the quake through the U.S. Geological Survey’s “Did You Feel It?” app, making it one of the largest response events for a single earthquake in U.S. history.
The shaking was felt as far north as Maine and as far south as Virginia, with an estimated 42 million people experiencing tremors across the U.S. East Coast.
Interestingly, while the earthquake’s epicenter was located in Tewksbury, New Jersey, damage in the immediate area was minimal. People in the epicenter region described only light shaking, which was surprising for a magnitude 4.8 event.
However, further away, in New York City, residents reported significant shaking, leading scientists to explore the cause behind this anomaly.
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The Science Behind the Earthquake’s Reach
After visiting the earthquake’s epicenter just hours after the event, researchers YoungHee Kim and Won-Young Kim from Seoul National University and Lamont-Doherty Earth Observatory were struck by the lack of damage in Tewksbury. The local response seemed understated for a magnitude 4.8 earthquake, which typically causes more noticeable damage.
However, the researchers noted that people in New York City, 65 kilometers away, had a completely different experience, with many reporting strong shaking.
Through their research, Kim and her colleagues proposed that the earthquake’s rupture direction might explain the wide impact. Rather than spreading in a typical radial pattern, the rupture propagated northeast, funneling seismic energy towards New York City.
This unusual rupture direction likely caused seismic waves to travel farther and with greater intensity, explaining why areas far from the epicenter felt the shaking so strongly.
How Seismic Waves Played a Role
To understand the earthquake’s behavior, the researchers focused on a particular type of seismic wave called Lg waves. These shear waves bounce back and forth within the Earth’s crust, and they tend to travel long distances with relatively little attenuation. The researchers modeled the earthquake using Lg waves to determine how the seismic energy was distributed.
Their model showed that the rupture was focused northeastward, which may have concentrated the shaking towards regions like New York City.
The earthquake’s behavior was further complicated by the geological characteristics of the region. In most northeastern U.S. earthquakes, seismic activity occurs along north-south trending faults.
However, the Tewksbury earthquake appears to have been caused by a combination of thrust and strike-slip faulting, which is uncommon for this region. This hybrid faulting mechanism contributed to the earthquake’s unusual rupture direction and its wide-reaching effects.
The Role of Fault Systems in Earthquakes
The Tewksbury earthquake also revealed important information about the fault systems in the northeastern U.S. While earthquakes in this region typically occur along well-established fault zones, the researchers discovered evidence of a previously unknown fault plane in the Tewksbury area.
This fault plane, which trends north-northeast and dips moderately, was identified through aftershocks detected in the region. This discovery suggests that there may be hidden seismic risks in the area that had not been previously accounted for.
Although the earthquake did not cause widespread damage in the immediate area, some localized damage was observed. A reconnaissance team from the Geotechnical Extreme Events Reconnaissance Association (GEER) documented cracks in drywall, fallen objects, and even the partial collapse of a stone façade on a historical building in nearby Lebanon, New Jersey.
However, the lack of significant destruction close to the epicenter remains one of the most surprising aspects of this event.
Implications for Seismic Hazard Assessment
The unusual behavior of the Tewksbury earthquake has important implications for earthquake preparedness and risk assessment in the northeastern U.S. The discovery of a previously unknown fault plane and the unusual propagation of seismic waves could change how we understand seismic hazards in the region.
Researchers now realize that areas in the eastern U.S., particularly those near hidden fault systems, may be at higher risk than previously thought.
The continued monitoring of aftershocks and the deployment of new seismometers by the U.S. Geological Survey (USGS) will provide valuable data on the region’s seismic activity.
This data will help scientists understand how the Earth’s crust responds to stress in the wake of a major earthquake and how future aftershock sequences may unfold.
Conclusion
The Tewksbury earthquake of 2024 serves as a reminder that even regions traditionally considered low-risk for large earthquakes, like the northeastern U.S., can experience significant seismic activity.
The earthquake’s unexpected behavior, including its wide-reaching impact and minimal local damage, highlights the need for more detailed seismic studies in the area.
By understanding the complex fault systems and the way seismic energy propagates, scientists can develop better risk models and improve earthquake preparedness in the region.
People May Ask
Why was the earthquake felt so far from the epicenter?
The earthquake’s rupture propagated northeast, funneling seismic energy toward New York City, which amplified the shaking in areas far from the epicenter.
Did the earthquake cause significant damage?
While there was some localized damage, such as cracks in drywall and fallen objects, there was minimal structural damage near the epicenter, which was surprising given the earthquake’s magnitude.
How many people felt the earthquake?
An estimated 42 million people across the U.S. East Coast felt the earthquake, with over 180,000 reports submitted to the USGS.
What makes the Tewksbury earthquake different from other earthquakes in the region?
This earthquake exhibited a hybrid faulting mechanism, combining both thrust and strike-slip faulting, which is unusual for the northeastern U.S. region.
What did researchers discover about fault systems in the area?
Researchers identified a hidden fault system in the Tewksbury area, suggesting there may be previously unrecognized seismic risks in the region.
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