This issue has bothered me for about 4 years, maybe I'm just too picky, but to me it possibly causes confusion amongst the general public when they
look at the Network Lists or read the news.
USGS are the worst, what the heck does (GS) magnitude mean?
and a new one this week, (UCMT)????
When you look at their Past 7 Days list or the 8-30 days Lists, they give a magnitude shown as MAG.
There is no indication of what scale it is.
The various scales used in seismology are listed here
To find out what scale they are talking about you have to go into Phase Data ( by clicking on the blue link of the individual quake on the list) and
then clicking on the Sciencific & Technical tab. Phase Data is on the list there.
Lets do one as an example
MAP, 6.3, 2010/05/25 10:09:06
on the Phase data we can see
MAGNITUDE 6.3 (UCMT)
then lower down (12 lines) we have
mb = 5.4 (226) ML = 0.0 ( 0) mblg = 4.5 ( 7) md = 0.0 ( 0) MS = 4.8 ( 2)
The numbers in brackets are the number of
stations used to collate the readings.
Which is all fine and dandy, too bad there is no ML, but being in the middle of the ocean as this quake was its probably irrelevant in this case.
So the 6.3 quake was really just a 5.4mb in disguise?????
As a cross check lets have a look at EMSC
, same event.
EMSC have it at 6.0 Mw
GEOFON do it as well as USGS, just giving a M= for magnitude. They have this event as a M= 5.6
In this case that event hasn't been checked by a human yet, but if you go to their Phase Data page (off that link page) they normally give mb, ML and
mB readings so you can assume they are talking about mb's when they refer to M=.
Having experienced many 5.0 - 5.6 magnitude quakes and a few low 6 magnitude at less than 100km distance, I can assure you that there is a vast
difference in the shaking between a 5.4 and a 6.3.
What are they (USGS) up to?
why post magnitudes at GS or UCMT or whatever which no one know what it means, why complicate things?, why not just post the magnitudes in mb which
anyone with half a clue can understand and relate to?
Its almost like they are pumping up the magnitudes for some reason.
[edit on 25-5-2010 by muzzy]