Earthquake magnitude is determined from the amplitude of ground motion as measured on a seismograph. In principle, energy should be proportional to amplitude squared, just as sound intensity is proportional to pressure squared. However, Richter noted that the energy released by an earthquake does not simply scale up. A larger earthquake ruptures a larger fault, over a larger range of depths, and over a longer time duration. So, in defining the magnitude scale, Richter empirically related magnitude to energy according to: log E = 11.4 + 1.5 M (for energy in ergs). Thus, for every increase in magnitude by 1 unit, energy increases by 10^(1.5), or a facor of 31.6.
Jeff Barker (seismologist and horn player) > > Date: Fri, 11 Mar 2011 14:22:51 +0100 > From: Hans Pizka <[email protected]> > Subject: Re: [Hornlist] BBC Phil in Japan > To: The Horn List <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=utf-8 > > > xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > The energy release of an earthquake, which closely correlates to its > destructive power, scales with the 3?2 power of the shaking amplitude. Thus, > a difference in magnitude of 1.0 is equivalent to a factor of 31.6 ( = > (101.0)(3 / 2)) in the energy released; a difference in magnitude of 2.0 is > equivalent to a factor of 1000 ( = (102.0)(3 / 2) ) in the energy released. > > xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > But in Japan there was a 7.2 quake two days ago, three shocks yesterday & > 42 shocks today between 05:46 A.M. & 01:49 P.M. local Munich time, means > 02:46 P.M. and 11:46 P.M. in Tokyo. > > But news did not talk about yesterdays heavy quake in Yuennan SW China with > 25 dead & over 250 injured, but CCTV9 broadcasted the Japan disaster for > several hours in their English program. > > Somebody out there to explain the above calculation in simplified words, > please ? > > > #################################################################################################### > > Am 11.03.2011 um 13:49 schrieb William Gross: > > > This is a major disaster for Japan, with tsunami affecting the > Philippines. > > Warnings have gone out to Gaum, Hawaii, Indonesia and the US West Coast. > > > > Early reports have it as an 8.9, by comparision the Northridge EQ that > his > > the LA area in 1994 was a 6.7. This equake is about 100 times more > > powerful. > > > > On Fri, Mar 11, 2011 at 6:25 AM, Lawrence Yates <[email protected] > >wrote: > > > >> I've just heard that the BBC Philharmonic Orchestra (based here in > >> Mancheter) who are on tour in Japan at the moment are safe after the > >> earthquake. Apparently they were going across a bridge in their coach > when > >> the earthquake struck. > >> > >> Lawrence > >> > >> > >> > >> -- > >> Lawrenceyates.co.uk <http://lawrenceyates.co.uk/> > >> _______________________________________________ > >> post: [email protected] > >> unsubscribe or set options at > >> > https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/bgross%40airmail.net > >> > > _______________________________________________ > > post: [email protected] > > unsubscribe or set options at > https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/hpizka%40me.com > > -- Jeffrey S. Barker Assoc. Prof. of Geophysics, Binghamton University Faculty Master, Dickinson Community (607) 777-2522 (Geology) (607) 777-2826 (Dickinson) http://bingweb.binghamton.edu/~jbarker/ _______________________________________________ post: [email protected] unsubscribe or set options at https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/archive%40jab.org
