According to an AP article in the Minneapolis-St. Paul StarTribune, the Chile 8.8 magnitude quake was a special type of earthquake called a “megathrust.” Megathrust quakes occur when a segment of a tectonic plate dives (thrusts) suddenly beneath another tectonic plate, otherwise known as a "subduction." According to Wikipedia, “Since 1900, all five earthquakes of magnitude 9.0 or greater have been megathrust earthquakes; in fact, no other type of known tectonic activity can produce earthquakes of this scale.” Although this quake was 'only' magnitude 8.8, it was the product of such a thrust.
The Chilean quake was similar to the 9.1 magnitude quake off Sumatra in 2004 that killed nearly a quarter of a million people. A large segment of one tectonic plate abruptly moved beneath another, causing an upthrust, violent shaking and a tsunami. This quake, in fact, ties in magnitude with a 1906 Equador quake as the 5th largest quake measured since 1900. In this instance, unlike the 2004 Sumatran quake, the distance to heavily populated shores was great enough to allow warning, and to attenuate the tsunami that emanated from it.
The USGS data shows that there have been 128 quakes worldwide since 1900 with death tolls that exceeded 1000 persons. It is not necessary for an earthquake be of particularly high magnitude to achieve devastation, In fact, quakes of magnitude 5.7 have killed as many as 2,800 people. Of the five quakes that exceeded 100,000 deaths, only one (the Sumatra quake of 2004) exceeded magnitude 8.0. The identified death toll in Chile has yet to exceed 1,000, but likely will. However, it is unlikely to approach any of the larger totals. Chile, unlike many of the other quake-victimized countries, has prepared for quakes for years.
There are, of course, other causes of earthquakes, all of which have to do with earth movements. For the most part, they are associated with lateral movements of plates against each other, or with smaller and slower subductions. Magma movement is volcanically active areas cause tremors, and of course volcanic explosions themselves cause strong quakes that can rival and even exceed tectonic quakes, including megathrusts.
And then there are “other” theories. There are people who believe that a device designed to investigate ionospheric activity has the power to move mountains (and tectonic plates). The “High Frequency Active Auroral Research Program (HAARP)” is in no way a weapon. Nor could it generate a hundred-gigaton energy release halfway around the world. It’s simply not that kind of device. It’s a high-frequency radio transmitter, not an “energy pulse” transmitter, as these folks claim. A theory propounded on a site called “Daily Paul” (yes, Ron Paul is featured), something called “…scalar electromagnetic superweapons called "Longitudinal Wave Interferometers," or "Tesla Howizters."” are promoted as the earthquake weapon. There are more.
The reality is, politicians and Secretaries of Defense notwithstanding, none of this is real. In truth, plate tectonic movements account for both volcanoes and earthquakes, with no need for outrageous conspiracy theories and unsubstantiated hyperbole. We're talking about moving billions of tons of rock, entire segments of continental shelves, all at once. None of the proposed "quake weapons" could even begin to release the one hundred gigatons, or more, of energy required. So, let’s leave the moonbats out of it.