In regard to John Lorenz’ article on massive stimulation by underground nuclear explosions (Historical Highlights, March EXPLORER): There were other studies done in 1965-1967 on the Nevada Test Site.
I was involved in very detailed geologic studies to discover the control of surface fracture patterns formed above explosions that were unrelated to and beyond the central chimney collapse. These were found to be attributable to through-going joint sets related to faults. The explosions jostled the joint-bounded blocks in the Paleozoic bedrock causing the fractures to propagate upward through 2,000 feet of alluvium and reproduce the joint pattern on the surface.
Where the joint pattern changed, the fracture pattern changed. The deeper shots produced better surface patterns.
Explosions close to the Yucca Fault also triggered fault offset.
Jostling of joint and faults by repeated earthquakes over long periods of time might explain the many surface lineaments present in relatively low seismically active areas such as the eastern United States.
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