We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Influence of Farallon Slab Loading on Intraplate Stress and Seismicity in Eastern North America in the Presence of Pre‐Existing Weak Zones.
- Authors
Hightower, Erin; Gurnis, Michael; Mao, Wei
- Abstract
Despite the stability of the continental interior, eastern North America has hosted many significant historical earthquakes. Seismicity concentrates within tectonically inherited structures, which can act as weak zones where stress accumulates. Within these zones, systematic stress rotations may be explained by long‐wavelength sources. We test the hypothesis that mantle‐flow driven by the Farallon slab contributes to intraplate seismicity via the reactivation of pre‐existing faults. We model the stress field using seismically constrained global high‐resolution finite‐element flow models with CitcomS. To isolate the slab's effect, we vary its buoyancy between a case of neutrality and a case with full negative thermal buoyancy derived from tomography. Low‐viscosity lithospheric weak zones located at failed rifts, loaded by a mass anomaly at depth, transmit elevated stresses to the overlying crust. The sinking of the Farallon slab drives localized mantle flow beneath the central‐eastern US, generating a large stress amplification of 100–150 MPa peaking over the New Madrid Seismic Zone (NMSZ). This stress amplification exerts a continent‐wide clockwise rotation on the stress field, which in the presence of weak zones reproduces some observed deviations of the seismically inferred SHmax from the regional borehole SHmax, bringing optimally oriented faults, closer to failure, some of which are associated with major historical earthquakes, including the Reelfoot Fault in the NMSZ and the Timiskaming Fault in Western Quebec. However, stronger lithospheric viscosity gradients, shallower weak zones, or weaker faults are still needed to fully reproduce the observed stress field in some areas. Plain Language Summary: Earthquakes in eastern North America are rare because they occur far from any active plate boundary. It is thought that pre‐existing weak zones in the crust or lithosphere loaded by far‐field tectonic or geodynamic forces can help concentrate stress and reactivate ancient faults. Specifically, we explore whether mantle‐flow driven by the sinking of an ancient tectonic plate (the Farallon slab) in the lower mantle beneath eastern North America contributes to this anomalous seismicity. We find that weak zones located at ancient tectonic structures, loaded by the Farallon slab at depth, increase stress in the overlying crust. The sinking of the Farallon slab drives localized mantle flow beneath the central‐eastern US, generating large stresses that peak over the New Madrid Seismic Zone. This stress amplification exerts a regional clockwise rotation of the direction of maximum horizontal compressive stress, consistent with some stress observations derived from seismic and borehole measurements. These rotations are important because they place stresses into more favorable orientations for reactivating faults. In particular, the slab and weak zones lead to instability on some faults associated with major historical earthquakes, demonstrating how mantle dynamics can influence seismic hazard in intraplate regions. Key Points: The Farallon slab induces a long‐wavelength stress high of 100–150 MPa across the central eastern US that peaks over the New Madrid Seismic ZoneThe Farallon slab causes continent‐wide clockwise rotation of SHmax; shallow intraplate weak zones enhance stress rotations and magnitudesStress perturbations from both the Farallon slab and intraplate weak zones heighten Coulomb failure stress on some faults associated with historical earthquakes
- Subjects
NORTH America; QUEBEC (Quebec); SLABS (Structural geology); PLATE tectonics; EARTHQUAKE zones; LITHOSPHERE; BUOYANCY
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2024, Vol 25, Issue 6, p1
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2024GC011493