Source of peak‐slip location discrepancy between seismicity–stress mapping and seismic/GNSS inversions

Determine whether the observed discrepancy in the location of peak slip between seismicity–stress imaging maps—constructed by correlating point‐source Coulomb failure stress change kernels with relocated aftershock distributions—and finite‐fault slip models inverted from seismic and global navigation satellite system (GNSS) observations reflects limitations of the seismicity–stress procedure or limitations of seismic and GNSS‐based slip inversion methodologies, as indicated by comparisons for events such as the 2004 Mw 6.0 Parkfield and 2021 Mw 6.0 Antelope Valley earthquakes.

Background

The paper introduces a seismicity–stress imaging procedure that maps potential, relative, static finite‐fault slip directly from seismicity by correlating point‐source Coulomb failure stress change (ΔCFS) kernels with the 3D distribution of aftershocks. This approach uses in situ information at depth and does not require prescribing a 2D slip surface, rupture speed, or rise time.

When applied to the 2004 Mw 6.0 Parkfield and 2021 Mw 6.0 Antelope Valley earthquakes, the seismicity–stress maps broadly agree with independent finite‐fault models but locate the peak slip closer to the hypocenter than most seismic/GNSS inversions. This systematic offset raises the unresolved question of whether the discrepancy arises from the seismicity–stress methodology or from biases and limitations in seismic and GNSS‐based slip inversions. Clarifying the source of this discrepancy is necessary to reconcile methods and improve confidence in finite‐fault reconstructions.