music
ambience: time-lapse earthquake recording
When it comes to the dynamics of planet Earth, little, if anything, happens in isolation, and earthquakes are no exception. I’m Jim Metzner, and this is the Pulse of the Planet.
We’re listening to time-lapse recordings of an earthquake. Faults are fractures in the Earth’s crust, which often occur at or near the boundaries between the Earth’s plates – the segments of the Earth’s crust which cover our planet like a giant jigsaw puzzle.
“What happens is, the plates stick at the boundaries because of friction, and they will stick for a while and build up stress. And then when the strength of the material is overcome, the strength of the rocks and the different layers deep into the Earth, then the whole thing breaks. It snaps. It ruptures. And that’s what causes the earthquake.”
Carol Raymond is a physicist at NASA’s Jet Propulsion Laboratory in Pasadena.
“We do know how much stress is building up. We just don’t know what the yield strength is. When is it going to break, and how much of it is going to break at a time? The size of an earthquake is governed by the patch of the fault that slips all at once and then how that energy is directed as it moves away from the point of the rupture.”
It turns out that when there’s activity at one fault, it’s likely to affect another.
“One of the most important things that’s been discovered about earthquake faults is that they exhibit a system behavior. So the faults interact. When one fault slips, it affects its neighboring faults, and they will respond, sometimes over long periods of time. New models are illuminating this behavior by modeling the whole fault system and showing how an earthquake on one fault may either increase the probability of an earthquake on another fault, or it may decrease it.”
Pulse of the Planet is made possible by the National Science Foundation.
music