A new piece of the earthquake puzzle
A paper, in the journal Science, comes out today, which presents new data and insight on earthquake physics*. Numerous experiments have been conducted by researchers all over the globe to approximate the physical conditions (lithology, pressure, temperature, etc.) where earthquakes occur. This paper presents a new type of experiment, which they call “Earthquake-Like Slip Events” (or ELSE experiments). So, what makes this procedure different? A short summary on the paper was already written, so I will not bother repeating it. I just wanted to elaborate on an aspect of ELSE that is pretty awesome.
Traditional rock mechanics experiments, in essence, slide rocks against each other, and (commonly) driven by a servo or electric motor — the rocks will slide at a prescribed velocity, for a given time, to reach a predetermined distance. Experimenters then extract valuable data about the sliding behavior (e.g., friction, heat, wear) of those rocks. The energy for these experiments are practically infinite; meaning, as long as you have electricity, the motor will drive the rocks as fast or long as you told them to go.
The ELSE experimental approach differs, in that a massive (5 ft. diameter, and 500 lbs.) flywheel stores rotational energy, then unleashed that energy to a pair of rock-discs. No additional power is supplied to the system when the flywheel and rocks are engaged. The rock determines how the fast it’s going to slip, and how long it will slip — not a motor. A visual aid would be like revving your engine at a stop sign, then popping the clutch to induce a burn out, or you can also watch the video below.
The finite energy approach might be a better approximation for how a large-magnitude earthquake slips, since the earthquake cycle consists of energy build-up and release**. And as far as I know, this machine is the first of its kind, but do give a comment below if you know of another!
* It is my opinion that the physics of earthquakes is somewhat of a beast — if you would like to form your own opinion, a “summary” on the topic can be read here [PDF].
** Note that I may be biased, since I am one of the authors of the paper.