CWP-776 Extracting the earth response from noise measurements

Recent research has shown that noise can be turned from a nuisance into a useful seismic source. In seismology and other fields in science and engineer-ing, the estimation of the system response from noise measurements has proven to be powerful technique. To convey the essence of the method, we first treat the simplest case of a homogeneous medium to show how noise measurements can be used to estimate waves that propagate between sensors. We provide an overview of research in physics that dates back more than 100 years that shows that random field fluctuations contain information about the system response. This principle has found extensive use in surface wave seismology, but can also be applied to the estimation of body waves. Because noise provides a continu-ous illumination of the subsurface, the extracted response in ideally suited for time-lapse monitoring. We present examples of the softening of soil after the 2011 Tohoku-oki earthquake, the detection of a precursor to a landslide, and monitoring the lunar soil.