The 5 April 2024 Mw ${\mathrm{M}}_{\mathrm{w}}$4.8 Tewksbury, New Jersey Aftershock Sequence Resolved With Machine‐Learning‐Enhanced Detection Methods

Abstract The Ramapo Seismic Zone (RSZ) in the Northeastern United States hosts frequent but poorly understood intraplate earthquakes, potentially posing a significant hazard to the nearby New York metropolitan area. The 5 April 2024, 4.8, Tewksbury, New Jersey earthquake, provides a rare opportunity to study the RSZ seismicity. We applied machine‐learning‐enhanced backprojection, matched‐filtering, correlation‐timing and double‐difference methods to continuous waveforms recorded at local and regional stations to detect and locate about 2,000 aftershocks ( 0.0) within the 74 days following the mainshock. They reveal a single, 51° east‐southeast dipping fault plane possibly abutting the Ramapo fault at depth to the north. Aftershock locations are consistent with a shallow (4 km) mainshock hypocenter with rupture propagating downward and terminating at a depth of about 6 km. A relatively high Gutenberg‐Richter b ‐value and a low aftershock spatial fall‐off rate suggest that the Tewksbury sequence activated a rough, immature fault.