The occurrence of an earthquake is probably one of the worst natural disasters. They cause devasting catastrophe and extensive losses. This sudden shaking movement of the surface of the earth can range in size from those that are so weak that they cannot be felt to those violent enough to destroy whole cities and even cause massive tsunamis in their wake.
The word ‘earthquake’ literally means ground-shaking. Seismologists also use the term in a broader sense when they talk about what happens below ground that produces the energy that causes the shaking. The rock-solid surface of the earth’s crust is constantly being stressed by forces exerted on them by natural processes, such as the movement of the earth’s lithospheric plates or the pressure built up by magma beneath a volcano. George Adams, College of Engineering Distinguished Professor at Northeastern University, has made significant contributions to our understanding of those sliding plates.
Adams identified a phenomenon regarding the behaviour of the waves generated when one very flat object slides over another. Seismologists, taken with the clarity the theory brought to their understanding of earthquakes, named it Adams Instability, after its progenitor, George Adams. “The theory of Adams Instability, in addition to its importance in the basic science of solid mechanics, allows more accurate predictions of the size of areas impacted by earthquakes,” says Hanchen Huang, professor at Northeastern University.
Adams who specialises in the area of Applied Mechanics says he developed the theory in ‘a very roundabout way.’ He explains, “I was investigating the behaviour of computer tapes as they were being pulled over a read/write head. I noticed that, intermittently, the thin film of air between the tape and the head collapsed, and the two made contact. During that sliding phase, a type of instability that had not been recognised before arose.” “I thought, ‘Maybe I can generalise this phenomenon’,” he says.
Adams’ research showed that this small disturbance grew bigger and bigger with time and distance. “During an earthquake, all sorts of waves are generated by the plates moving against each other,” he says. “It’s those waves, their instability, that do the damage as they travel,” giving birth to a theory that found major recognition. “One of the nice parts about applied mechanics is that what I learned 40 years ago can still be used today but for different applications,” Adams says. “I tell my students that what they’re learning today they will still be able to use 30 years from now,” he concludes.