This is interesting...
Earth can serve as a giant detector for theoretical ripples in the fabric of space-time given off by stars, black holes and other massive objects in deep space, researchers say.
Scientists reasoned that Earth itself could be used as a gravitational wave detector. One might potentially detect the combined effects of gravitational waves streaming through the planet by analyzing its seismic activity — that is, how much Earth shakes.
In the new study, researchers focused on gravitational waves with frequencies of 0.05 to 1 hertz, a band largely overlooked by other detection efforts. Potential emitters in this range include pairs of cosmic objects such as white dwarfs, neutron stars and black holes as they orbit each other. Gravitational waves with such frequencies also may be given off by rapidly spinning neutron stars known as pulsars.
http://www.space.com/25781-earth-moon-gravitational-wave-detector.html
I am wondering if certain types of rocks may be more sensitive to that frequency?
Maybe... Koolau basalt??? ;)
Cosmo