Are Low-Frequency Earthquake Moments Area- or Slip-Limited? A Rock Record Examination

The seismic moments observed for low-frequency earthquakes (LFEs) vary over multiple orders of magnitude, even where the LFEs occur within families of similar events. Although this variability is typically interpreted to record a scale-limited process at the LFE source, neither the slip per LFE nor the rupture area can be determined from seismological constraints. Here, we examine incrementally developed slickenfibers that have been proposed to record LFEs in exhumed subduction zones. These structures form through repeated, micron-scale slip events across dilational irregularities in the fault plane, which are punctuated by cementation and sealing in the interstitial space. By statistically analyzing the geometry of inclusion trails delineating slip-parallel mineral-growth increments, we constrain the variability in slip per inferred LFE and test end-member hypotheses regarding the controls on LFE moments. We find that that the slickenfibers exhibit characteristic slip increments, favoring a slip-limited model that requires large variability in LFE rupture areas.

Automated summary

This study examines the variability in slip per inferred low-frequency earthquake (LFE) and tests different hypotheses regarding the controls on LFE moments. By analyzing the geometry of slickenfibers, the study finds characteristic slip increments and supports a slip-limited model with large variability in LFE rupture areas.