Pre-Seismic Magnitude Compression Across Six Tectonic Regimes: Evidence from K–R Critical Slowing-Down Indicators in Nine Earthquake Catalogs

We introduce the K–R excitation–regulation framework, a coupled ordinary differential equation (ODE) system that produces critical slowing-down (CSD) indicators from earthquake magnitude sequences. The K–R ODE integrates excitation K and regulation R event-by-event: dK/dt = α tanh(σ) − βK, dR/dt = γK − δR, where σ = (M − Mc)/(9.5 − Mc). An identical eight-step pipeline is applied to nine independent catalogs spanning six tectonic regimes: Japan and Chile (subduction), San Andreas (strike-slip),