Damage great in substantial buildings, with partial collapse. Intensity 9: Violent - Damage considerable in specially designed structures well-designed frame structures thrown out of plumb. Intensity 10: Extreme - Some well-built wooden structures destroyed most masonry and frame structures destroyed with foundations. (USGS) I’ve never heard of this intensity scale. Meanwhile, one hypothetical magnitude 7.8 earthquake on the San Andreas fault could send “extreme,” or Intensity 10, shaking across most of urbanized Southern California. So, for instance, a magnitude 8.2 - probably the strongest earthquake that could hit Southern California on the San Andreas fault - would produce an astonishing 178 times more energy than the magnitude 6.7 Northridge earthquake in 1994. Geological Survey has a calculator that can help you make these calculations.
The moment magnitude scale measures the movement of rock along the fault, and accurately measures larger earthquakes, which can last for minutes and affect a much larger area the Richter scale did not accurately record such quakes, Jones said.
On the so-called Richter scale, a magnitude 8 on a seismogram was 10 times bigger than a magnitude 7.īut the Richter scale was eventually scrapped in favor of what is known as the moment magnitude scale. Magnitude was about how big the waves were on a seismogram at a particular distance from the epicenter. Originally, the definition of magnitude related to seismograms, in which machines used an ink stylus to record rapid motions on a rolling drum of paper that would measure shaking.
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