Hi All. The mini swarm of quakes NE of Viola got my attention so I thought I would see if I could locate the fault that they might be associated with. The fault map I use is the 1994 version by Charles W. Jennings. My map program is the DeLorme Topo USA 4.0 that allows me to duplicate the fault map, or the maps on the USGS site.

What I found was kind of interesting. They are located within or very close to a linear fault zone that starts just a little ways NW of Lake Tahoe and runs NW to a point just north of Viola.

There are about 20 cinders cones located along this zone and beyond with the majority of them located in the Mt. Lassen area. Mt Lassen by the way is located at the NE edge of the indicated zone.

The Red Rock Mountain seismograph does show it to be a tectonic quake.

Using the ANSS catalog that has a starting date in 1949 for this area I found that there have been 9 quakes within a 5 radius with a magnitude of M>3.0 and larger. Take Care…Don in creepy town

1949/11/16 08:04:20.00 40.5300 -121.5800 3.20 ML BK
1953/01/02 19:05:02.00 40.5000 -121.6000 3.20 ML BK
1954/06/16 16:03:26.00 40.4800 -121.6000 3.60 ML BK
1955/11/11 12:18:00.00 40.5000 -121.5700 3.20 ML BK
1956/02/14 21:02:11.00 40.5000 -121.5700 3.30 ML BK
1956/03/18 10:17:41.00 40.5200 -121.6000 3.50 ML BK
1956/03/18 10:22:03.00 40.5200 -121.6000 3.70 ML BK
1956/06/28 21:57:31.00 40.5000 -121.6000 3.10 ML BK
1958/12/02 05:06:15.00 40.5000 -121.6000 3.10 ML BK