The 4.8 magnitude earthquake that shook New Jersey and the Northeast on April 5th, 2024, led to the discovery of a previously unknown fault line. This new fault line may explain the unusual shaking pattern, with stronger tremors felt miles from the Tewksbury Township epicenter.
While the epicenter experienced minimal damage, areas like New York City, 40-50 miles away, reported significant shaking and minor damage. This unusual seismic activity puzzled researchers, prompting further investigation.
A study led by Won-Young Kim of Columbia Climate School’s Lamont-Doherty Earth Observatory revealed that the earthquake’s energy travelled downwards towards the Earth’s crust and mantle boundary, roughly 20 miles underground. Upon reaching this boundary, the energy was redirected upwards, focusing the strongest shaking under New York City. This explains why areas further from the epicenter experienced more intense shaking.
The newly discovered fault line, running south to north and dipping eastward at a 45-degree angle, is believed to be responsible for this unusual energy redirection. Unlike vertical faults, this angled fault channeled the seismic energy northeastward, causing the unexpected shaking pattern.
This discovery highlights the difference between Northeast and West Coast earthquakes. While West Coast earthquakes are often caused by shifting tectonic plates, Northeast quakes originate from ancient, reactivated fault zones formed millions of years ago during the separation of North America and Europe. These areas continue to adjust, causing occasional seismic activity.
Researchers estimate similar magnitude earthquakes occur in the Northeast approximately every 100 years. However, the region has the potential for significantly larger earthquakes, up to magnitude 7, every few thousand years. Such a large-scale earthquake in New Jersey today would be catastrophic.
Following the April earthquake, scientists deployed seismometers to monitor aftershocks and map the region’s fault lines more accurately. This information will be crucial in reassessing earthquake hazards and updating building codes to mitigate future seismic events in the densely populated Northeast.
This recent earthquake highlights the importance of understanding regional seismic activity and preparing for potential earthquakes, even in areas not traditionally considered high-risk. The new fault line discovery underscores the need for continued research and preparedness to minimise the impact of future earthquakes in New Jersey and surrounding areas.