Hi All,

Yesterday, when sitting in on a lecture given by S. Prejean regarding Mammoth, I got a view about an interesting period in 1989 when it appears Mammoth was close to an eruptive stage. Around June of 1989 a swarm of earthquakes began under Mammoth Mountain. This lasted for a period of six months, however, the peak time was between June and August. The area in question is approximately 37.63 - 118.05, directly under the mountain.

There were several interesting features during the swarm in that none of the quakes were greater than 3.0M and the seismograms revealed spasmodic bursts, which were a chain of brittle failure earthquakes. They look like tectonic quakes which are connected, versus harmonic tremors. The smallest number of quakes occurred at the 2km depth, the largest at 5-6 kms and the magmatic intrusion at 7-9 kms. She reported these are, non-double couple quakes.

It was at the same time in which the tree kill in the area began from the Co2 emissions and Helium 3 was also noted at the time.

Frankly, I found this piqued my curiosity in how these quakes compared to the activity in 1980 when they had four 6.0 quakes. I wonder if the same type of spasmodic earthquake activity was occurring at that time, or if they simply had four earthquakes. So some further research is needed to ferret out the information.

From the information I think it provides some clues to how the Mammoth area activity develops and it is easy to see that it would be more likely if a future eruption occurred it would not happen in a short period of time, but more likely over a longer period with many clues in evidence. From what I understand the Co2 problem with the tree kill is on the wane, which is certainly good news. This comes from sources other than through this lecture, so I wanted to make note of that. The tree kill when observed is one of the most dramatic sites I think one can see in a forest. To see an area with lush green pine trees and find an area where they are absolutely stark white with not a pine needle in sight, lets you know something very serious occurred.

Also another curious matter is that in August 1989 we had a foreshock to the Loma Prieta earthquake and frequently many notice what appears to be a link between Mammoth and the Loma Prieta general area. Thus one must ask, is there any correlation between the two or, simply an odd anomaly?

These lectures are only for 12 minutes, so you can imagine they have to move along at a rather rapid pace and trying to take handwritten notes as they breeze from one diagram to another is no easy task. So this is the most I could secure for you without bringing video camera. LOL

Don may wish to post some of his thoughts on this as well, as he does tend to remember some things more than I do and has a better general understanding of some of the data.

Petra