Youqian Zhao1, Andrew Curtis*1,3, Brian Baptie2,
1School of Geosciences, University of Edinburgh, UK, 2British Geological Survey, UK, 3Department of Earth Sciences, ETH Zurich, Switzerland
A wide range of applications require 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 possibilities 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 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.
We present a well-commented MATLAB code that implements this location method – see www.geos.ed.ac.uk/eip. The code 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 apply the code to a selected data set of the New Ollerton earthquakes, England, to demonstrate its validity. A way to assess the quality of the location results is also provided.