Identification of Earthquakes and Explosions Using Amplitude Ratios: The Vogtland Area Revisited

Identification of seismic events is a major scientific issue in the framework of verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Of special interest in this context is the identification of the numerous low-yield mining or blasting events, especially those occurring in the same area as earthquakes, such as the Vogtland area in the border region of Germany and the Czech Republic. Seismic events in this area were investigated by WU¨ STER (1993, 1995), who achieved complete discrimination using measures of spectral decay and spectral variance at the GERESS array and a quadratic discrimination function. A subset of these events, for which ground-truth information is available, has been analyzed in this study using multivariate statistical analysis. Various parameters based on measurements from seismic waveforms of the broadband stations of the German Regional Seismic Network (GRSN) and short-period elements of the GERESS array are tested for statistical significance in a linear regression analysis, in particular spectral amplitude ratios for the Lg phase and Pg/Sg amplitude ratios. The subset includes a total of 35 explosions and 24 earthquakes. The results of our study argue that identification based on spectral Lg and highfrequency Pg/Sg ratios is promising. However, discrimination success is strongly varying from station to station; thus, weighting according to station success rates could improve the overall identification capability.