Hi All. Every now and then I learn something new and when I do I go looking for confirmation. Sometimes I find what I'm looking for and then there are times I don’t. More often as not I find a lot gray area. This appears to be the case here.

Wiens and recent Washington University graduate Hersh Gilbert found that large, deep earthquakes producing abundant aftershocks occur in "cold" regions limited entirely to the Pacific Southwest. They occur where rock descends relatively quickly into the inner Earth, resulting in material that is colder than elsewhere in the world.

There findings suggest that different subduction zones -- places where a plate descends beneath another plate, leading to earthquakes -- have different aftershock production rates and that the aftershock production rates are related to the temperature of a region. Wiens used a mathematical model to determine the thermal structure of the different earthquakes, which showed whether a subduction zone was hot or cold.

Analyzing 40 years of data from nearly two dozen large, deep earthquakes (occurring between 250 and 400 miles into the Earth) in South America and the Pacific region, Wiens has shown that South American and Japanese earthquakes have very few aftershocks, while those in the Pacific Southwest beneath the Tonga, Mariana’s and Indonesian islands have lots of them. The South American earthquakes occur in hotter regions; the Pacific ones in cold areas. Okay nothing new here. Of course not everyone agrees with this theory, but there are some who do.

This got me to thinking about earthquakes in Nevada, particularly why in some locations we have a lot of aftershocks and in others we have very little or in some case’s a vigorous, but short lived aftershock sequence.

The Great Basin is a region that is very active, and its mountain ranges are all geologically quite young. As the crust beneath the Great Basin stretched, it has grown thinner, and therefore there is a high rate of heat flow between the mantle and the surface. It may very well be that this high heat flow near the surface has the opposite affect on quakes near the surface as opposed to those that are deep. Just recently there were two quakes in Nevada. One was located in northeastern Nevada and the others near Tonopah Junction. The quake in northeastern Nevada had almost no aftershocks if any at all, while the quakes near Tonopah had a very vigorous, but short lived aftershock activity. It could be that the high heat flow in the Tonopah area is the cause of these quakes. There is however a problem with this theory. I’m not sure as to the thickness of the crust in northeastern Nevada. If it is the same, or near the same as it is in western Nevada then it could be said that high heat flow has very little to do with quakes in the western Nevada area as well as eastern California in the Owens Valley area.

The forces of crustal faulting and volcanism are described by the theory of plate tectonics and can be observed to be continuing today. For example, the White Mountains are currently raising an average of more than an inch a year, and the Owens valley to the west is also sinking at about the same rate. This causes numerous earthquakes in this region. It is this stretching that caused Long Valley Caldera and is also causing the on going activity at present time. It may be that the next eruption at Long Valley Caldera may not be the results of magma rising in the area, but the collapse of the resurgent dome. The stretching and pulling apart would be like removing the supports from under the dome. Take Care…Don in creepy town

• Great Basin