Relative source location using coda wave interferometry: method, code package, and application to mining induced earthquakes

Abstract

A wide range of applications requires relative locations of sources of energy to be known accurately. Most conventional location methods are either subject to errors that depend strongly on inaccuracy in the model of propagation velocity used, or demand a well-distributed network of surrounding seismic stations in order to produce reliable results. A new source location method based on coda wave interferometry (CWI) is relatively insensitive to the number of seismic stations and to the source-to-station azimuthal coverage. It therefore opens new avenues for research, for applications in areas with unfavourable recording geometries, and for applications which require a complementary method. This method uses CWI to estimate distances between pairs of seismic events with similar source mechanism recorded at the same station. These separation estimates are used to solve for the locations of clusters of events relative to one another within a probabilistic framework through optimization. It is even possible to find relative locations of clusters of events with one single-channel station. Given these advantages, it is likely that one reason that the method is not used more widely is the lack of reliable code that implements this multistage method. We therefore present a well-commented MATLAB code that does so, and present examples of its applications. It can be used with seismic data from a single station channel, and enables data recorded by different channels and stations to be used simultaneously. It is therefore possible to combine data from permanent yet sparse networks, and from temporary arrays closer to the source region. We use the code to apply the location method to a selected data set of the New Ollerton earthquakes, England, to demonstrate the validity of the code. The worked example is provided within the package. A way to assess the quality of the location results is also provided.