By the count of seismologist Lucy Jones, a Caltech research associate, Southern California has felt 15 independent seismic sequences this year, with at least one magnitude 4 or higher earthquake. That's the highest annual total in the last 65 years, surpassing the 13 seen in 1988. The most recent — a magnitude 4 — struck before dawn Sunday near Ontario International Airport. Just in Ontario, one of the most populous cities in San Bernardino County, there have been five earthquakes of magnitude 3 or higher over the past month.