Source directivity, signal decorrelation, spectral modulation and analysisof spatio-temporal patterns of multiple explosions

Spectral modulation is used as a criterion for discriminating multiple mini ng explosions from earthquakes and single blasts. Features in the spectra o f regional arrivals from quarry blasts may be explained by the spatio-tempo ral configuration of shot patterns and are explored via a model based on sp atial waveform decorrelation and propagation delay (directivity) effects. T he phenomenon of decreasing modulation with decreasing average phase veloci ties of the seismic wave arrivals can be attributed to a trend of decreasin g similarities of waveforms with increasing distance between individual exp losions making up the shot pattern for the respective arrivals. Rescaling o f the modulation patterns with respect to frequency can be explained by the Doppler effect. The postulated relationship between shot pattern layouts and sizes, togethe r with their firing sequences, on one hand, and the similarities and differ ences in modulation characteristics among the various regional arrivals, on the other hand, can be used to derive information about the mining practic es in a region that is otherwise not accessible. Moreover, such analyses co uld be utilized for detecting unusual activities in the CTBT monitoring sys tem.