shakers are part of the deal if you live in Calif. over time you learn a few things. understanding them isn't a perfect science but one thing that many will tell you is the ground "can" get irritated with smaller shakes in advance of a major jolt.there isn't surefire linkage here but when a cluster of smaller shakers start showing up I look at this the same way storm watchers get uptight when the sky darkens.
http://www.businessinsider.com/san-ramon-400-earthquake-swarm-california-two-weeks-2015-10#ooid=52MmVoeDoJhJAoXO5y4SOCe16YN5TBhg