Quote:
Originally Posted by 3506string  |
Well, actually, the 5.2 was based on the body wave, giving the body magnitude M
b. The 5.6 is based on the seismic moment, giving the moment magnitude M
w, which has essentially supplanted the outdated Richter magnitude, M. The Richter magnitude is based on measurements taken off the Wood-Anderson seismometer, which has physical limitations on the magnitude of earthquake it can measure.
The seismic moment is a calulated value involving the area of the rupture surface, the distance the rupture surface slipped, and the roughness, or coefficient of friction of the rupture surface. It provides a more meaningful estimate of the energy released during an earthquake. The moment magnitude is based on the seismic moment, and the calculation scales the magnitude to resemble the older Richter magnitude. When the news media report the Richter magnitude of an earthquake (or "temblor" a term only the media use), they're actually reporting the moment magnitude, but they don't know any better.
Interestingly, the M
w5.6 earthquake released at least 25 times more energy than the earlier M
w4.7.
OK, now that we've got that covered, you'll be interested to know that my wife's aunt owns the package store in Eufala, Oklahoma, about 60 miles from the epicenter. I emailed her this morning but she hadn't gone down to the store to see if there were any bottles lost. I'll update you later.
