Hi Petra. I plotted the quakes on my topo map and found that there could have possibly been two swarms or clusters of quakes in the area in 1977. The first swarm, which could be associated with the 4.5Md quake located at 37.9228n/122.1600W, was 2.9 miles NW of Orinda. There was a 3.9Md foreshock for this quake. The most recent swarm is located about 2.6 miles NW of Orinda at Chaparral Peak

On 01/24/1977 there was a 3.1Md at 37.8792N/122.2267W. This is about 2.3 miles west of Orinda. There is a small swarm of quakes consisting of 19 quakes associated with this quake. The distance between the quake on 01/08/1977 and this quake is 4.9 miles. There are a couple of quakes in between these two, but for the most part most of the quakes appear to be associated with the largest event in each swarm/cluster.

My fault map does show some faults in the immediate area, but they are unnamed. The nearest major fault is the Hayward fault and is to the west of these quakes.