Applied Mathematics Colloquium

In theory, the cross-correlation of ambient noise recorded at two spatially separated sensors will produce the Green's function that describes the wave propagation between the two points.  This leads to the idea of using seismic surveys to map the subsurface without using active sources. In practice, there are a number of assumptions between interpreting the cross-correlation as a Green function that are not always borne out in practice.

The technique will be illustrated with a dense seismic survey that was carried out in the Long Beach area of Los Angeles. We will infer the shallow velocity structure in the area by seismic interferometry and show its effect on earthquake waves. We will show the promise and problems of turning this passive survey into an exploration tool. The same dataset is also used to examine the behavior of micro-earthquake in the area.

The work is done in collaboration with Fan-Chi Lin, Dunzhu Li, Victor Tsai, Asaf Inbal and Jean-Paul Ampuero.