Hi All. The current swarm of quakes south of Long Valley Calderas are occurring on the Hilton Creek Fault. On 05/27/1980 a 6.3Ml quake occurred at 37.47N/118.81W. The epicenter of that quake is 4.8Km north of the current swarm. It would seem that the activity should be at or very near the epicenter of that quake. All most all of the activity in the area since that quake has been in and around this area.

The quake activity actually started within an 8Km radius of the current swarm in 1978 with a 3.4Ml. Since then there have been 358 of magnitude 2.4Ml and larger within an 8Km radius of the current swarm with the majority of the quakes south of the 6.3Ml quake.

To my way of thinking this is a little too much to except as aftershocks of the 1980 quake. While it is true that most of the quakes are tectonic there never the less are some long period quakes associated with this kind of increase in activity.

Here are the types of quakes that can be seen within a volcano and the surrounding area.

The fracturing of rock as the magma moves upward causes short-period earthquakes.

Long-period earthquakes indicate increased gas pressure within the volcano.

Harmonic tremor results from sustained movement of magma underground.

I will admit to having some trouble in being able to tell short period quakes from very small tectonic quakes.

Long-period quakes are not hard to spot, but there are times when noise within the system can cause a problem, which can look a lot like a long period quake.

To the best of my knowledge no harmonic tremors have been seen at Long Valley.

All of this still doesn’t answer the question as to why there are so many quakes in this one spot. Are they an indication of a new volcano being born? Is it the forming of a new dike? Or are they nothing more then a fault that is still on the move?

I think I’m just going to sit back, put my feet up and wait and see. Take Care…Don in creepy town.