3 temblor was a separate, "triggered earthquake" caused by ground waves
from the Chilean quake.
Also, a disparity in travel time between two sets of ground waves
suggests that sound travels faster through the material in some directions than it does in others.
The slow, rolling ground waves
that spread along Earth's surface from that temblor caused the seafloor beneath the grounded iceberg to oscillate up and down about 2 centimeters every 20 seconds or so.
Even though scientists can distinguish between the ground waves
caused by earthquakes and those from explosions, it's often difficult if not impossible to tell a nuclear blast from a chemical explosion, such as one caused by TNT.
Since then he has collected reports made by other seismologists who saw ground waves
in connection with 26 quakes around the world.