Repeating seismic events in China

About 10% of seismic events in and near China from 1985 to 2000 were repeating events not more than about 1 kilometer from each other. We cross-correlated seismograms from similar to14,000 earthquakes and explosions and measured relative arrival times to similar to0.01 second, enabling lateral location precision of about 100 to 300 meters. Such precision is important for seismic hazard studies, earthquake physics, and nuclear test ban veri. cation. Recognition and measurement of repeating signals in archived data and the resulting improvement in location specificity quantifies the inaccuracy of current procedures for picking onset times and locating events.