Earthquake-aftershock puzzle solved, say physicists

Earthquake-aftershock puzzle solved, say physicists

Noise threshold: are aftershocks a part of the main earthquake event?

The idea that smaller earthquakes (aftershocks) follow major earthquakes is a well-established concept in geophysics. However, aftershocks are not explained by the avalanche model that is used to describe earthquakes and similar phenomena such as the cracking of solid materials. The model dictates that events such as earthquakes are random and therefore there should be no correlation between successive earthquakes. Now, Sanja Janićević, Lasse Laurson and colleagues at Aalto University in Finland have shown that this discrepancy could simply be a result of how aftershocks are measured. Writing in Physical Review Letters, the physicists describe experiments in which they monitored the cracking of a solid material. They found that when they set the detection threshold of their apparatus at high values – to avoid measuring noise – an individual avalanche event appeared as a sequence of seemingly unrelated events. However, when they reduced the detection threshold, what had previously appeared to be aftershocks were actually part of the main avalanche event.
http://physicsworld.com/cws/article/news/2016/dec/02/flash-physics-earthquake-puzzle-solved-scientists-write-to-trump-nuclear-pasta-delays-neutrinos