New Jersey’s earthquake risk was first evaluated in 1998, later revised in 2005, and revisited much more recently. The New Jersey Geological Survey is expected to release a new land survey within the upcoming year (2023/2024,) paying special attention to the newly assessed fault lines.
NJGS has identified earthquakes over the last few centuries that have impacted the state, which has helped outline specific regions of concern today.
Redbank sand has been primarily (and iconically) detected by USGS in Red Bank, Monmouth County, and surrounding counties. The sediment is a red sand rich in glauconite, an iron potassium phyllosilicate mineral. Compounds within surrounding sands within the soil have accelerated the red sand’s oxidation, turning the red color to a darker green or brown. Beneath this layer is a more solid, rock-like clay layer of black sand with a presumed thickness of 100 ft.
USGS identifies the sediment as underlying the “Rancocas formation and [overlying] Navesink formation.” These formations have been identified in land surveys as the barriers separating New Jersey's shores and sandbars from the rest of the country.
This information has opened the door for geologists exploring one (soon-to-be many) of New Jersey’s new faultlines: The Red Bank Fault Line. Dozens of earthquakes have been reported and documented in the region over the years, clearly illuminating the need for a line to be drawn… on the map of fault lines.