Natural Earthquakes vrs Mine Collapse The discussion in the press involves a lot more than basic physics. Egos, liability, and more are behind the comments reported in the press.
>From the physics standpoint, point-explosions (whether quarry blasts, nuclear >tests, or most mine collapse) produce seismic records that are quite distinct >from earthquakes. Earthquakes are messy things. They release stress that has built up along a fault over a long period of time. The fault does not tear all at once, so there is a fairly long period of time during which the rupture occurs. Once that first failure occurs, then there is a period of stress readjustment and �aftershocks� when additional failure occurs at points close to the initial fracture, which release the rest of the built-up stress. Therefore natural earthquakes produce a seismic record that is very messy and complicated, with a lot of wiggles and juggles. Point explosions are relatively neat. The seismic record produced is usually a sharp big jiggle followed by a decreasing series of smaller wiggles � like a single beat on a big drum. That is how we can tell if a foreign power makes an unreported nuclear test. Such a test does not produce the same kind of messy seismic signal as that produced by an earthquake. A large mine collapse can be somewhere in between, so it is not necessarily immediately clear what occurred. The first bang caused by the initial mine collapse can be followed by secondary collapses as stress is redistributed and adjacent parts of the mine collapse as a result. Each collapse event, however, produces a distinct and sharp signal. So the academic seismologists have very good reasons when they say �It does not look like a natural earthquake�. My bet is with them. Dirtdoc --------------------------------------------------------------------- Visit our website: http://texascavers.com To unsubscribe, e-mail: texascavers-unsubscr...@texascavers.com For additional commands, e-mail: texascavers-h...@texascavers.com
