here's nbc's melissa coronado. >> reporter: a swarm of earthquakes rattled starting at 4:33 a.m. >> my dogs were going crazy. they freaked out. they were running for the hills. so that got my attention. usually the little ones i just kind of like shake off. this one got my attention a little bit. >> reporter: the 3.9 magnitude earthquake got lots of peoples attention with people as far away as oakland and san francisco tweeting that they felt it, too. >> everything started shaking like all the glasses. everything was shaking and everybody was like what's going on? >> when i looked in the backyard the pool had, you know, the old tidal wave thing going there. >> reporter: as this map showed the jolt was followed by a series of less powerful after shocks in the san ramon area. >> the one that scares everyone, of course, is the biggy. let's pray we don't get any of those anytime soon. >> reporter: a reminder we live in earthquake country. we can't predict when they strike, but we can certainly be prepared. >> that comes with living in california. it's part of the program. >> yeah, it's par