Understanding Frictional Forces Using Lab-Generated Earthquakes %

Earthquakes have been a cause of mass destruction such as the 2011 Tohuku earthquake off the coast of Japan. The earthquake generated a tsunami that ended up destroying the Fukushima Power Plant and displaced the residents of that town. In order to design preventative measures against such devastating events, seismologists and engineers alike have been studying earthquakes to learn about their origin and mechanism. However, since much of the action takes place deep inside the earth, seismologists are unable to measure earthquakes directly at the source which is why a team of researchers at Caltech created and observed the first-ever small-scale laboratory-generated earthquakes.

In order to simulate an earthquake, the researchers used a special transparent block of plastic known as Homalite which has similar frictional properties to that of a rock. Next, two pieces of Homalite are put together under high pressure which shadows tectonic properties that slowly build up along a fault line. After that, a small wire fuse was placed under the blocks which reduced friction at that location and triggered a very fast rupture to travel to the surface of the block which would produce intense shaking. In order for researchers to study this phenomenon, high-speed imaging technology recorded the evolution of stresses along the fault as the rupture approached the surface of the block. This Digital Imaging Correlation (DIC) measures small changes in the location of individual points throughout the material over time showing how stress and strain dynamically evolve during an earthquake.

The team of researchers hope that physical insights into the dynamics of an earthquake can help geoscientists create a more accurate computer model of earthquake ruptures propagating along real-world thrust faults. Only this way could models be designed to ensure the safety of residents in areas highly prone to earthquakes or tsunamis.