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Schlagwörter:
Quarry blast discrimination, Statistical approaches, Time and frequency domain methods, Armutlu Peninsula, Turkey
Zusammenfassung:
Different methods to discriminate between quarry blasts and earthquakes in seismic records are applied and compared. Test area is the Armutlu Peninsula in northwestern Turkey, where microearthquakes and quarry blasts occur within the same area. The vertical component of a 360″ broadband sensor is used for the discrimination analyses. Eighty-seven seismic events with up to M = 3.0 duration magnitude and maximum 23-km epicentral distance are chosen from the first 7 months of 2014. Five different methods, (1) time distribution, (2) amplitude peak ratio (As/Ap–log(As)), (3) complexity-spectral ratio (C–Sr), (4) coda wave decay rate (Qc), (5) power spectrum density (PSD), and two statistical approaches, linear discriminant function (LDF), quadratic discriminant function (QDF), are performed through all seismic events. The results are then compared to a “gold standard” obtained by a careful manual investigation. Two functions are obtained for As/Ap–log(As) method and four functions with different distances (0–13 km, 13–23 km) are estimated for C–Sr method. Accuracies of LDF and QDF for As/Ap–log(As) method are 88.5% and 87.4%, respectively. For C–Sr method, an accuracy of 89.8% is obtained for both, LDF and QDF, for distances up to 13 km, whereas for the distance range between 13 and 23 km from the epicenter, the accuracies are 85.7% and 89.3% for LDF and QDF, respectively. According to the Qc, the success rate is calculated as 91.9%. 93.1% accuracy of PSD technique provides the most successful results. All methods were used for a final decision according to which 27 earthquakes and 55 quarry blasts could be identified, while five events are misclassified. Overall, a 94.2% success rate could be obtained for our test data set. For the Armutlu Peninsula, the PSD method proves to give reliable solutions. Nevertheless, this cannot be generalized and thus a combination of different methods is recommended for areas with high tectonic and mining activity.
