Earthquakes can trigger aftershocks on
faults near the epicenter (or the same fault
that generated the quake), and it has been
recently suggested that they can also trigger
smaller quakes on different faults that are
farther away. This is because the energy
produced during a large earthquake can shift rock
around, changing the orientation of the stress
field or frictional properties on a fault.
This shift may cause the rocks to move to a more
unstable orientation, thus causing slip along that
This was documented in Asia in 2012, when a
moment-magnitude 8.6 earthquake in the Indian
ocean triggered two 5.5 magnitude earthquakes off
the coast of Japan in the following days
(Delorey et al., 2015, Science). The
authors of this study actually suggest that
surface waves are the main trigger for what they
call "cascading earthquakes" that can occur
after large quake. Basically, as the surface waves
move through the crust, they cause several small
"cascading" tremors that shift the rock around
enough to eventually cause a large earthquake
along a large fault. In this case, the 5.5
magnitude quakes happened along normal faults at a
subduction zone. However, surface waves
(called either Love waves or Rayleigh
waves), are formed.
S and P waves are what we call "Seismic"
waves. This means they travel through the
earth, and through different materials. The way
they move through materials doesn't inherently
causes disturbances. However, S and P waves can
cause other waves. When a P or S wave hits a
surface, they can create other waves which are
destructive. A fault is a type of surface, so
it could be effected.
When waves collide with each other, it doesn't
have the same result as when solid objects
collide. When two waves collide we call this
interference because depending on how they
collide, there can be different results. The
result of the collision can be either
destructive interference (one wave cancels out
the other wave) or constructive interference (they
add together to be stronger).
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