Hi All. No matter how hard I try I can’t get it out of my mind that the activity at Mount Saint Helens and Long Valley Caldera are connected. As to how I have no idea.

I have talked to many seismologists about the possibility of there being a connection between the two in the form of the Eastern California Shear Zone (ECSZ). I have heard that it is felt by some that it may extend all the way up into British Colombia. There have been others who have said “no way” and then there have been some who have said that there is no way of knowing for sure one way or the other.

Mount Saint Helens erupted on 05/18/1980 and one week later Long Valley Caldera woke up with a series of four M>6.0+ quakes two of which were non-double couple quakes.

Since that time there has been unrest at Long Valley Caldera consisting of “harmonic tremors” the venting of Helium 3 and the continued up lifting of the resurgent dome although there have been a few occasions where it descended. There have been all kinds of indications that there is unrest at Long Valley Caldera, but no clear indication as to what is in the offering.

In the mid to late 1997 there were a large number of “long period” earthquakes under Mammoth Mountain along with the increase in the venting of Helium 3. This was taken as to mean that fresh magma had been injected into the magma chamber beneath the area. This time period was one of the periods where USGS almost declared a “yellow condition” however this wasn’t done.

We now have an ongoing quake swarm at Mount Saint Helens however there is no evidence that an intrusion of magma similar to that of 1998 is underway. Such earthquakes are common at St. Helens, but a swarm with this many earthquakes has not been recorded for several years, most recently on November 3-4, 2001. There was an increase in earthquake activity at Mount St. Helens in the spring and summer of 1998 when hundreds of earthquakes per month, most smaller than M=2, were detected at depths as great as 9 kilometers (6 miles). An intrusion of magma, or molten rock, deep under the volcano and resulting increased gas pressure in the conduit that leads to the lava dome likely caused this increase in earthquakes.

This may be nothing more then a mere coincidence, but were now having a quake swarm in the area of Adobe Hills. For those who aren’t familiar with this area it is covered with cinder cones and other volcanoes numbering around 20 to 25 in total. From what I have been able to discover these volcanoes date from historic time to about 2 million years ago.

Prior to this we had a series of earthquakes in the Lake Tahoe area that resulted in the uplifting of the area. These quakes numbered over a thousand. Prior to that we had the quake swarm in the area of Lakeview, Oregon. There most likely isn’t a connection, or if there is it’s very subtle.

Could it be the ECSZ or something else? Keep in mind that this is nothing more then speculation of any old man who has a healthy curiosity for why things do what they do and what they mean. Take Care…Don in creepy town