03-17-2011, 05:53 PM
Hello Livium,
You see, major earthquakes are not most of
the time alone. This means that, whenever a great earthquake
occurs this will be come accompanied by other earthquakes, before or
after the "big one".
The ones occurring before are technically speaking so called "foreshocks"
and the ones occurring after the big one are so called "aftershocks".
In the case of the recent, unfortunate Japanese earthquake there seems to have
occurred two foreshocks before the big one (M=9.0).
Then a lot of aftershocks have occurred.
The reason of such aftershocks is somehow simple to explain, imagine something
that is at rest (in this case the plates). What the earthquake does is to generate a sudden slip over a place of
the plates that was "locked" during many years. In other words, it generates a sudden movement of one plate with respect the other. So after the earthquake occurs, the fault plane/plates contact is unstable which causes aftershocks until the plates get at rest once again.
And then the cicle begins again. loading("at rest")+energy release(earthquake/unloading)+rest(loading process begins again)
I hope this helps
Regards
You see, major earthquakes are not most of
the time alone. This means that, whenever a great earthquake
occurs this will be come accompanied by other earthquakes, before or
after the "big one".
The ones occurring before are technically speaking so called "foreshocks"
and the ones occurring after the big one are so called "aftershocks".
In the case of the recent, unfortunate Japanese earthquake there seems to have
occurred two foreshocks before the big one (M=9.0).
Then a lot of aftershocks have occurred.
The reason of such aftershocks is somehow simple to explain, imagine something
that is at rest (in this case the plates). What the earthquake does is to generate a sudden slip over a place of
the plates that was "locked" during many years. In other words, it generates a sudden movement of one plate with respect the other. So after the earthquake occurs, the fault plane/plates contact is unstable which causes aftershocks until the plates get at rest once again.
And then the cicle begins again. loading("at rest")+energy release(earthquake/unloading)+rest(loading process begins again)
I hope this helps
Regards