Ambient Noise Tomography
Overview
Recent advances in seismic methods use coherent signals, recorded at a pair of stations, to image the underlying structure without using earthquakes or explosions. This low amplitude seismic “noise,” present at all seismic stations, is generated from a wide range of sources, from waves and wind along shorelines to those resulting from local, man-made activities such as operating cars, trucks, and trains. It is known as “Ambient Noise,” or noise in the background. By cross correlating long-time series between stations, the common signal is retrieved while the incoherent energy cancels out, leaving a signal that reveals information about seismic velocity between the two seismometers. Making measurements on these signals and using an array of stations for many ray paths allows for determining a three-dimensional image of the subsurface shear velocity. This method is known as Ambient Noise Tomography (ANT).
Ambient Noise Tomography opens up new possibilities when imaging the subsurface at many different scales and complements traditional passive source tomography. Seismic imaging without the earthquakes! ISTI seismologists are experts in using ANT to decipher the subsurface velocity structure beneath your region of interest. Contact us today for a quote.
The slideshow includes the workflow for ANT data processing.
