Hi All. It seem James H. Dieterich of USGS is closer to finding the proof about his theory in regards to earthquake swarms. Earthquakes swarms as some of you may know are large groups, or clusters of quakes where there isn’t a one single quake that can be pointed to as being the main event with the rest of them being aftershocks.

Earthquake swarms, Stein noted, do not exhibit "typical" earthquake behavior in which a mainshock occurs, followed by a series of aftershocks that become less frequent with time. Instead, in a swarm there is a sustained high rate of earthquakes. Eventually, the seismic action stops or peters out. Swarms are most common in volcanic areas, such as in Hawaii, the Pacific Northwest, Alaska, Yellowstone, and parts of northern and southern California. However, such swarms also may occur on tectonic faults, including California's famed San Andreas. Why swarms occur has always been a mystery.

A couple of years ago there was an earthquake swarm in the Coso Volcanic Field in the Southern California area. There is magma under the area, but as to how close it is to the surface I don’t know. Steam used in geothermal fields isn’t caused by water coming in contact with magma, but with hot rocks above the magma. The same thing applies to hot springs. The question has been asked many times by others and myself as to the cause of that swarm. Was it magma on the move, or did one of the faults that are known to be in the area cause it, or could it have been a combination of the two? To the best of my knowledge no surface deformation was seen during the swarm however magma can’t be ruled out. It can move horizontally and as such it wouldn’t cause any deformation at the surface although I’m not 100% certain of that.

Anyway it’s things like this that keep seismologists up late at night. They develop theories only to take them apart and then start all over again. Hope you enjoy. Take Care…Don in creepy town

• Earthquake Swarms