Hi All. Some of you are aware that I have been following the activity at Long Valley Caldera for almost 3 years now. During that time I have accumulated a considerable amount of data. Most of this has come from sources outside USGS, which for the most part I can’t confirm. I save that to a disk in the hopes that I may be able to confirm it at a later date.

There is however some that I can use as it has been posted on the web. One article is by Dr. Bruce Julian with USGS. The thing that caught my interest were the last four lines in the last paragraph in the below statement. I have not been able to learn the location of these quakes, but suspect they are near Mammoth Mountain as that is where one of the hot spots are located. This hot spot was pointed out at the recent AGU conference. How ever they may have been at the south rim as this is the location of the instruments. Take Care…Don in creepy town.
In order to obtain higher-quality data, a dense, 65-station state-of-the-art network of digital, 3-component seismometers was deployed in the Mammoth Mtn./south caldera rim area for 3 months in the summer of 1997. The objective of this field project was to record local and regional earthquakes in order to study structure and processes in this, the most active part of the Long Valley area. Of particular interest is repeat tomography of the south moat of the caldera, which has generated massive amounts of seismic activity over the last 25 years, which has probably caused changes in Earth structure there. Moment tensor analysis of both the shallow volcanic earthquakes and the deep LP earthquakes beneath Mammoth Mtn. has the potential to reveal their genesis processes and to show whether these involve the movement of geothermal and/or volcanic fluids.
The network was deployed as a co-operative project involving University of Durham, the U.S. Geological Survey and Duke University, U.S.A. The sensors deployed include 56 3-component short-period seismometers and 6 broadband instruments. Data were recorded digitally at > 100 sps. Broadband seismometers record well ground movements with periods as long as 100 s and frequencies as high as 50 Hz. The inclusion of some broadband instruments is a great advantage in volcanically-active areas as volcanic processes e.g., magma flow, are capable of generating diverse exotic seismic events with much energy outside the traditionally-recorded short-period range.
Shortly after the network was installed, a seismic crisis occurred within it. Over 1,600 earthquakes with local magnitudes up 3.5 were located there by NCSN alone, and approximately 10 times this number will be locatable with our much denser network (http://www.dur.ac.uk/~dgl0grf/mammoth.fig2.ps). At the same time inflation of the resurgent dome greatly accelerated and the two phenomena are clearly linked. About 100 LP earthquakes occurred during the deployment period, 30 of which were well-recorded by our network. A superb dataset is thus available with which to address the research goals. Of particular interest will be to study the link between the short-period earthquakes that occurred during the seismic crisis and the dome inflation. The earthquakes clearly resulted from increased stress in the roof of an activated part of the magma chamber and might be expected to have components of crack opening in their mechanisms.

• Long Valley Caldera