Well...being as how I stirred things up a little with that last neartly O/T thread...I thought I would get back on the straight and narrow (or is that just the narrow?) trail and stick with closer to On Topic stuff.

Here we go again with the deep focus earthquake problem.:

1) Deep earthquakes have radiation patterns consistent with double couples (associated with shear faulting). [ref: Prof. Lay]

2) Theoretically quakes cannot occur below 70 kms (due to rocks getting packed ever tighter due to presumed rising temperatures and pressures with depth...thus closing off all cavities...and causing rock to flow under such stress). Above a certain pressure (presumed matched with depths of several hundred kms) , lab experiments show that brittle fracture is prohibited as well as frictional sliding processes.

3) (The proposed state change in the structure of the rock/minerals at high pressures to attempt to explain the deep focus quake is lacking in that the energy to intiate is "missing" (i.e. not explained as to origin)). In addition, if a mineral changes to a denser phase very suddenly, conditions for an implosion might exist. However, seismic evidence / signatures of implosion events are easily recognized. Deep focus quakes mimic shallow quakes in that the intial motions are downward in some areas and upward in others. Also S waves are stronger in deep quakes than P waves just as they are in shallow events. This is interpreted as slip (shear) taking place and this could not be an implosion event. [ref. Dr. Frohlich]

4) Most deep-focus quakes happen near subduction zones however not all of them. Romania and Hindu Kush have no active subduction zones yet have had deep-focus quakes.

5) Most deep-focus quakes are almost never followed by aftershocks.

6) And finally, Kozlovsky has reported with increasing depth in the Kola Peninsula hole (> 7 miles deep) "the expected increase in rock densities was not recorded. Neither was any increase in the speed of seismic waves nor any other changes in the physical properties of the rocks detected. Thus the traditional idea that geophysical data obtained from the surface can be directly correlated with geological materials in the deep crust must be re-examined."

- Also, an expected basaltic layer ( a reflector - aka "Conrad discontinuity") expected at 5 km depth was not yet found even at 12 km depth...and must exist at as even greater depth). MisIdentification of reflected seismic waves may have caused them to believe a layering of rock existed.

- The same deal happened at the German Oberpflaz Forest hole.

- A similar deal happened in France when searching for a magnetic anomaly running north-south through the Paris Basin.

- The standard answer is "It must be deeper"...yet what about the assumptions regarding seismic wave travel times...Are these correct ? If they are not then what other "conclusions" may be drawn?

- In 1980, a study of seismic waves indicated that a particular layer existed at a given depth in AZ. ==> A fault zone was found at the location of the layered reflections but the composition of the rocks did not change enough to account for the strong reflections. (This is what I believe they call a Hint).

Comments (especially with data) are welcome.

$.02