Coda Wave Interferometry (CWI)

Coda is a Latin word which means tail. It is a term used to describe a passage at the end of piece in music. In seismology, this term is used to describe the terminal part of a seismogram. The later waves arrival is scattered because of the complexity of the earth, their paths are long and complex. This part of the seismogram is a mix of all types of waves, which is called the coda wave. Coda Wave Interferometry is an ultrasonic technique for detection of subtle changes in inhomogeneous media. It is based on calculation the cross-correlation of squeezed/stretched or time shifted part of a measurement to a reference to quantify the (average) of velocity change.