It also has been used to pinpoint the locations of more than 7,000 seismic events along California's Calaveras faultline near Morgan Hill. Stanford graduate student Eva Zanzerkia used the technique to show that some aftershocks of the 1992 Landers earthquake occurred along well-defined but previously unidentified structures and that an observed progression of earthquakes along these structures may be triggered by water deep in the Earth's crust. The arrows show arrival times as determined by standard methods. These are subject to considerable uncertainty, which can be greatly reduced by alignment of entire waveforms to measure arrival times consistently. A blur of circles of different sizes denotes aftershocks of different magnitudes along California's Calaveras fault.
Improved locations result in sharper mapping of faultlines.