Jesse-Lee Dimech, who is completing his PhD in Geophysics at Victoria, says seismic energy is useful for looking inside planets.
“Using the energy from earthquakes, or in this case, moonquakes, we can gain insight into the composition and structure of the Moon.”
Between 1969 and 1972, five of the Apollo missions successfully placed seismometers at landing sites on the Moon, which recorded ground motion and radioed this information back to Earth. Contained in this dataset are more than 13,000 moonquakes that were recorded up until 1977.
“I’m working on categorising and detecting moonquakes using the Apollo seismic dataset, as well as some extra datasets not previously used for this purpose. This particular work is being done in collaboration with Dr Renee Weber, my advisor at NASA, and Dr Brigitte Knapmeyer-Endrun, a scientist at Germany’s Max Planck Institute for Solar System Research.
“It's a great opportunity to work with some of the world's top planetary seismologists. By applying new seismic analysis techniques we may be able to learn new information about the Moon—even from such an old dataset,” says Mr Dimech.
One of those new techniques is shear wave splitting analysis, a key research interest of Professor Martha Savage from Victoria’s School of Geography, Environment and Earth Sciences, who has collaborated with Mr Dimech to undertake the first shear wave splitting analysis off Earth.
“When seismic waves travel through layers of rock they split in much the same way light does when it hits a crystal. By measuring how much splitting occurs, we can infer physical properties from the rock, such as stress and fracturing, the presence of fluids, and rock laminations,” says Mr Dimech.
Another technique, developed by Victoria’s Associate Professors Richard Arnold and John Townend, is a statistical method of examining the geometry of the faults responsible for earthquakes.
“I applied this technique in my PhD to earthquakes we found in the upper mantle—the layer beneath the crust—which was able to tell us what type of faults produced them. We will be using a modified version of this code to understand the type of faulting associated with ‘deep’ moonquakes, which are situated about halfway between the Moon’s surface and its core.
“I’m continuing to work with Professor Savage and Associate Professor Arnold while I’m at NASA. New Zealand has some great scientific talent and I’m excited about maintaining these relationships and building new ones.”
Some of the techniques Mr Dimech uses may also be useful in helping NASA learn about the composition of Mars when they land a seismometer there in two years’ time as part of the InSight mission to Mars.
Australian-born Mr Dimech says he has loved space since he was a child, and a postdoctoral role at NASA is the culmination of a lifelong ambition.
“I was actually pen pals with Australia’s first astronaut Andrew Thomas. We exchanged several letters when I was a kid, and I even talked to him on the phone once, as well as fellow astronaut John Glenn who just happened to be in the office at the time. They definitely inspired me. I was also the youngest member of an astronomy club. I’ve always been fascinated by NASA.”