Cessation of Nearby Low‐Frequency Earthquake Activity Following the December 2024 M w 7.0 Mendocino Earthquake: The Likely Role of Pore Pressure Reductions

Abstract Earthquakes affect surrounding fault systems through multiple mechanisms. Here, we examine a rare cessation of activity in 27 families of low‐frequency earthquakes (LFEs) that likely reflect fault creep at the southern edge of Cascadia subduction, near the Mendocino triple junction. These sources usually exhibit nearly daily activity but were shut off for ∼7–25 days following the December 2024 moment magnitude ( M w ) 7.0 Mendocino fault earthquake. Based on modeling, we infer that this cessation was not caused by induced shear stress, which was slightly encouraging of slip, but rather by combined clamping normal stress and reduced pore pressure. This mechanism, which isn't captured in the common effective friction simplification, may have strengthened the fault and inhibited creep, without requiring fluid outflow. Observed variations in LFE cessation times are not predicted by modeled stress changes alone and may instead reflect differing source dimensions or subtle variations in LFE fault geometry.