On June 29, 1925 at 6:42 a.m. reported Santa Barbara shaking for 18 seconds. The Richter scale was not yet invented, but semiologists estimate the main shock was 6.3 magnitude and the epicenter located offshore.

For more info, please read the original article by Santa Maria Times :
https://santamariatimes.com/lifestyles/columnist/julia_mchugh/julia-mchugh-1925-santa-barbara-earthquake-95-years-ago-this-week/article_ccd0713e-288b-5658-9511-37e683447e09.html