Improved Stress Drop Estimates for M 1.5 to 4 Earthquakes in Southern California From 1996 to 2019

We estimate Brune-type stress drops for over 70,000 southern California M 1.5–4 earthquakes from 1996 to 2019 using a P-wave spectral decomposition approach. Based on our recent work documenting hard-to-resolve trade-offs between absolute drop, drop scaling with moment, high-frequency falloff rate, and empirical corrections path attenuation terms, we adopt new approach in which the average corner frequency of smallest within short distance each target event is fixed constant value. This removes any true coherent spatial variations among events but ensures that seen larger are real not an artifact inaccurate corrections. Applying this across California, document agree previous work, such as lower-than-average Salton Trough, well small-scale along many faults aftershock sequences. observe apparent increase moment 3–4 earthquakes, their spectra can be fit equally self-similar models rate shallower than f−2.