An aftershock of magnitude 6.1 rocked Haiti just over
a week after the 7.0 earthquake. The original earthquake, which killed hundreds of
thousands of people and disrupted the living circumstances of many more, has
been followed by a series of smaller earthquakes.
Will there be anymore aftershocks? That was
the question a colleague asked me earlier this morning. I replied that there
have been most likely over a hundred aftershocks in Haiti, and that most never made a
public statement because they were a hundredth the size.
Earthquakes when measured by the Richter scale (which is
most widely used) use a logarithmic scale. The base ten measurements tell you
that a 7.0 earthquake is ten times the magnitude of a 6.0 Magnitude. The recent
6.1 aftershock left its impression while the other aftershocks documented by the
U.S. Geological Survey (USGS), varying from 4.0 upwards approximately 4.9, have
not had nearly the same impact.
After a large earthquake like the one that struck Haiti last week,
it is typical to experience several smaller earthquakes, termed aftershocks.
These smaller events allow the rigid tectonic plates to elevate any residual
stress while the fault line remains lubricated by recent activity. We will most
likely see a decline in occurrence and magnitude over the following days, weeks
or possibly even months until the activity hibernates in a lower stress
environment.
References:
http://www.freakygossip.com/2010/01/earthquake-hits-haiti-2nd-haiti-61-aftershock-latest-updates/
http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/region/S_America.php
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