posted on Mar, 24 2011 @ 07:13 PM
Originally posted by Ryanssuperman
I'm just looking for an explanation as to why Japan is still getting quakes, as strong as 6.6, 13 days (and counting) after the 9.2? Are these
aftershocks? Do aftershocks usually last this long for a quake of this magnitude?
Thanks for any info you can give me.
edit on 24-3-2011 by Ryanssuperman because: (no reason given)
An answer from my dad, seismologist with the USGS:
After a main EQ (the 9.0 in the case of Japan's recent big one), the plates involved continue to adjust to their new states of stress. These
adjustments cause more earthquakes--the aftershocks. All other things being equal, and on average, there are lots of aftershocks at first then they
slowly die off with time. The falloff is commonly exponential (same formulas as for compound interest only in reverse).
Again on average, within a year of the main EQ, the fault will produce one EQ, one magnitude less than the main EQ. So Northeast Japan could expect an
after shock as large as M8, which might cause a smaller Tsunami.
10 aftershocks two magnitudes less (M7)
And 100 aftershocks as large as M6.
and so on down the magnitude scale.