6 events in Passaic County with a date

The Culprit Below

New research into NJ 2024 earthquake revealed unknown fault

By: Amanda Wallace
NorthJersey.com
USA Today Network - New Jersey

..... More than two years after an earthquake rattled the Garden State, a group of researches are continuing to unravel its unusual nature, officially naming a previously unmapped fault where the quick occurred.
..... The 4.8-magnitude earthquake struck near Tewksbury on April 5, 2024, rattling homes from Boston to Washington. The U.S. Geological Survey said the quake was felt by 42 million people, triggering a rare response. The ISGS Online portal, which crowd-sources first-person reports of shaking, received nearly 184,000 entires the most from any U.S. earthquake.
..... Scientists were immediately shaken into action, later telling NorthJersey.com that the quake was unusual.
..... Based on existing models, the epicenter of the earthquake, Tewksbury Township, should have sustained substantial damage. It did not, according to a study from the Columbia Climate School's Lamont-Doherty Earth Observatory.
..... Meanwhile New York City shook much harder than expected and was left with some minor damage. The high number of aftershocks were also unusual, the study said.
..... An analysis from scientists at South Korea's Seoul National University suggested that the earthquake occurred on a previously unmapped fault in the area.
..... Now, recently published research is helping to piece together some of those curiosities, designating the Mountainville Fault.
..... "The 2024 Mw4.8 Tewksbury, New Jersey earthquake occurred near the -300-km long Ramapo Fault, which, although constituting the largest regional fault, is mis-oriented for slip in the current tectonic stress regime," reads the study, published in the Journal of Geophysical Research: Solid Earth. "The upward projection of aftershocks aligns with the topographic trace of a previously unmapped fault zone 3.5 km west of the epicenter."
..... Here's a look at some of the study's findings and why they are significant, according to lead researcher Folarin Kolawole, a structural geologist and professor at Columbia University.

The Mountainville Fault

..... In April 2024, just hours after the earthquake hit, Kolawole and two postdoctoral researchers came to the epicenter area to take advantage of the rare opportunity to gather new data in real time amid the aftershock.
..... Kolawole and his team have since determined that the prominent structurally mature Ramapo Fault is not to blame, and the fault that caused the 2024 quake is an immature fault that shows up at the surface in the Mountainville area of New Jersey.
..... Though there are many faults in the Garden State, the Ramapo Fault is the most well-known, running about 185 miles from New York through New Jersey, beneath Passaic, Morris, Somerset and Hunterdon counites, and on into Pennsylvania.
..... It runs beneath Pomptom Lakes, Riverdale and Pequannock, just to the south of Lake Valhalla in Montainville, under Booton, beneath Bernardsville and Far Hills, and into Hunmterdon County, near the epicenter of th4e 2024 earthquake.
..... The Ramapo Fault may seem the obvious suspect behind the 2024 quake, but Kolawole said the epicenter was too far to the west.
..... The location of the main shock is on the western flank of the Ramapo Fault, which is not supposed to be the case, Kolawole said, adding hat the Ramapo is an inclined fault that goes downward to the east. If the epicenter had been east of the fault, scientists could have considered that it occurred deep in the crust somewhere in the Ramapo.
.....Other seismological techniques also ruled out the Ramapo Fault, Kolawale said. To figure out which fault caused the earthquake, Kolwole and his team plotted the main shuck and the aftershocks. They visited the area to look at the rocks and see if they have characteristics that suggest that a fault is there what the orientation of the fault might be and if it's similar to what the earthquake of the fault at depth.
..... "If it is the same, that means we are literally on the fault," Kolawole said.
..... He and his team determined that the Mountainville Fault zone fits the category of an immature fault, and that the structural characteristics that suggest that its immaturely is consistent with what has been observed in previously studied earth quack hosting faults along the East Coast.
..... "The key point is there are structural features that manifest false maturity and the observation we made in the field of the Mountainville Fault is very similar to those of other faults," Kolwole said, adding that scientists are seeing an increase body of evidence that suggest earthquakes hosting faults along the East Coast are immature faults.
..... A similar example is th4e fault that caused the 2020 earthquake in Sparta, North Carolina, he said.
..... "It seems to me that we're seeing this common pattern of major earthquakes in the East Coast that suggest that less prominent, immature faults might be a bigger earthquake hazard than we have recognized in the past," Kolawole said. "Because typically we focus on the big, prominent, well-developed faults. We ignore the less prominent ones."

What scientists still hope to learn

..... Although they have determined the groin of the 2024 earthquake, Kolawole said, scientists still have much to learn, including what the triggering mechanism was and whether there is a history of a major surface-breaking earthquake on the Mountainville Fault. If so, Kolawole said, there could be the potential for a bigger-magnitude earthquake than the one in 2024.
..... Another curios aspect scientists hope to tackle is the abnormal level of shaking that was felt in the New York City area during the 2024 quake.
..... Finally, Kolawole aims to see if there were any precursory signs that could have hinted at a critical earthquake hazard in the Tewsbury area before the earthquake broke.
..... We're still trying to understand if there's anything that any of our regional seismometers had pickled up in the moths to years preceding that 2024earthquake that could have hinted at a potential for a bigger earthquake magnitude before it happened." Kolawole said. "I know we're doing the work after the fact, but whatever we can learn an help us to forecast on the areas where such might happen again in the region and in other parts of the world."
..... Overall, Kolawole said, the main implication of this research is raising the importance of blog-prominece fault zones as critical earthquake hazards on the East Coast.
..... Going forward, he said, scientists need to continue looking at locations where small earthquakes are happening and pay attention to the subtle, less prominent fault zones.
..... "It's a lot of work, but that is what we have to do," Kolawole said. "We have to dedicate effort to looking at the rocks, identifying the sort of fault zones, and looking at which ones are favorably oriented to the original stress field, because those are going to be the critically stressed faults that could break a bigger earthquake in the future."

HOME