Answer: There have been numerous aftershocks detected following the recent
magnitude 9 megathrust earthquake. The U.S. Geological
Survey National Earthquake Information Center (USGS/NEIC)
continues to record many newly occurred aftershocks. As
of
1:00PM, MST, December 29, sixty-eight aftershocks have
been cataloged. The largest occurred about three hours
after the main shock and is now assigned a magnitude of
7.1. Thirteen of the aftershocks thus far cataloged have
magnitudes of 6.0 or larger. There have been no reports
of tsunamis being generated from the aftershocks. We
know from past experience that the number of aftershocks
will decrease with time. However, the number of
aftershocks can be quite variable. There might be short
episodes of higher activity as well as lulls in
activity, but the overall trend will be for fewer
aftershocks as time goes by. Seismologists are not able
to predict the timing and sizes of individual
aftershocks.
The number of cataloged aftershocks will be constantly
changing, as new aftershocks occur and as USGS/NEIC
analysts newly locate aftershocks from the first few
days after the earthquake. Magnitudes assigned to
individual aftershocks may change somewhat as new data
come in.
