Sensitivity of Focal Mechanism and Depth of the 2024 M4.8 Tewksbury Earthquake to Seismic Velocity Model and the Impacts on Earthquake Ground Motions
Description:
On April 5th, 2024, a magnitude 4.8 earthquake occurred in Tewksbury Township, New Jersey. The earthquake was felt by millions of people from Virginia to Maine and beyond and generated more than 180,000 U.S. Geological Survey (USGS) “Did You Feel It?” felt reports, the largest number of any earthquake. Ten percent of the reports came from New York City, 65 km east of the epicenter, and modified Mercalli intensities exceeded V within 10 km of the earthquake. There is significant uncertainty about how shallow the earthquake ruptured and modest uncertainty regarding the earthquake’s focal mechanism. This combination of uncertainty impacts expectations for the frequency-dependent spatial variability of ground motions, hazard, and risk.
Ground-motion simulations of notable earthquakes in the central and eastern United States are limited and typically assume one-dimensional Earth structure. In this study, we use a three-dimensional seismic velocity model to investigate the spatial variability of earthquake ground motions and the effects of nearby sedimentary basins and the soft post-glacial sediments overlying hard basement rocks beneath New York City and elsewhere. We perform earthquake ground-motion simulations up to 0.5 Hz using the Cartesian version of the three-dimensional spectral-element wave-propagation solver SPECFEM3D over a region 280-km wide by 260-km long by 77-km deep. Topography and subsurface geophysical structure are assigned using the USGS National Crustal Model and imposing a minimum shear-wave velocity of 200 m/s. Moving to a higher frequency and lower minimum shear-wave velocity is possible but would require greater computational resources and, at some point, a better-resolved velocity model. We use earthquake time-series from 13 broadband seismic stations in the region that have a relatively uniform azimuthal distribution and epicentral distances ranging from 76 to 131 km to compare with synthetics and explore the effects of topography and three- versus one-dimensional seismic structure on focal mechanism and depth solutions and discuss the impact on earthquake ground motions in the region.
Session: Accuracy and Variability of Physics-based Ground Motion Modeling [Poster]
Type: Poster
Date: 4/15/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Oliver
Student Presenter: No
Invited Presentation:
Poster Number: 80
Authors
Oliver Boyd Presenting Author Corresponding Author olboyd@usgs.gov U.S. Geological Survey |
Ebru Bozdag bozdag@mines.edu Colorado School of Mines |
Haiyang Kehoe hkehoe@usgs.gov U.S. Geological Survey |
Morgan Moschetti mmoschetti@usgs.gov U.S. Geological Survey |
|
|
|
|
|
Sensitivity of Focal Mechanism and Depth of the 2024 M4.8 Tewksbury Earthquake to Seismic Velocity Model and the Impacts on Earthquake Ground Motions
Session
Accuracy and Variability of Physics-based Ground Motion Modeling