Funny you should mention this area as this area of California is my number 1 expertise and one I consider myself an expert in. I have studied this region extensively so here is my 2 cents.

Yes, this is the area that the Concord and Calaveras live with the Calaveras ending in Alamo and the Concord beginning about 4 miles to the north.

First let me address this recent activity before giving some info on the geology of this area. For most part this activity is somewhat normal for that region. That whole region experiences a 1-2 mag quake almost every other day. They probably get one 3-4 once a year. And every 10 years on average they get a crazy swarm of 3s and 4s followed by 100s of 2s and 1s that last weeks and has everyone that lives there on pins and needles. Then the swarms go away as fast as they came.

Now for the more ominous interesting part. Indeed, as you mentioned, the Calaveras ends in this area. These swarms every 10 years I speak of happen around the Calaveras but never on it and extend on either side of the zone from that 3.0 in Alamo down to Dublin (580/680 interchange). Now there is like 10% chance this segment of the Calaveras from Sunol up to Alamo is going to fail in a 6.5+ quake in next 30 years. But here's the kicker. Unlike other fault lines in the bay area that have defined traces, the Calaveras more or less loses its trace north of 580. They are confident it exists, and, is locked, however unlike its neighbor, the Hayward to the west and San ANdreas further west and its sister segments of Calaveras to south, there is no "creep" as it runs under 680 to Alamo. I've read papers questioning (like the do the San Andreas under Salton Sea) if there is solid, locked structure all the way to Alamo or if it breaks up into a bunch of little faults all the way to the Concord fault. One paper I read suggested they'll only know for sure if a rupture starts in SUnol and goes all the way up to Alamo in 6+ event.

One clue is that they know there was a large quake in the region in 1865. But the magnitudes and EXACT locations very. Its been said it was a 5.5 to 5.8 to 6.6. Some have placed the epicenter right in the area of these quakes you see and others further east and south in Livermore. Soooo its kinda tough to know.

The 3.0 after midnight happened in EXACT spot as a 5.4 in 1954. NOBODY talks about that quake when people speak of the seismic quiet the bay area was under from 1906 on. They point to the Daily City quake as the only 5+ till 1979, but not true.

Also the newly found Mt. DIablo thrust fault is in this area as well and maybe driving these quakes off the Calaveras. ANyway this area is a very interesting one to follow in California.