Seismic monitoring of the Comprehensive Nuclear-Test-Ban Treaty using waveform cross correlation requires a uniform coverage of the globe with master events well recorded at array stations of the International Monitoring System. The essence of cross correlation as a monitoring tool consists in a continuous comparison of digital waveforms at a given station with waveform templates from the global set of master events. At array stations, cross correlation demonstrates a higher resolution because the time delays at individual sensors from master and slave events are the same but they may differ from theoretical ones used in standard beamforming. In the regions where master events and thus waveform templates are available, one can reduce the amplitude threshold of signal detection by a factor of 2 to 3 relative to standard beamforming and STA/LTA detector used at the International Data Centre. The gain in sensitivity corresponds to a body wave magnitude reduction by 0.3 to 0.4 units and doubles the number of detected events. This gain is crucial for seismic monitoring under the CTBT. The coverage by real master events is sparse and confined to areas with historical seismicity, however. In two parts of this study, we investigate the possibility to populate the global grid with real and synthetic master events. In Part I, we replicate a high-quality master event over a regular grid several hundred kilometers from its actual position. In Part II, we model waveform templates using synthetic seismograms with the aim to apply them in aseismic zones. Both approaches are tested using the aftershock sequence of the April 11, 2012 Sumatera earthquake (Ms(IDC)=8.2). We used sixteen master events to recover the aftershocks in the Reviewed Event Bulletin of the IDC.
Seismic events found by waveform cross correlation after the announced underground nuclear tests conducted by the DPRK on 12.02.2013 and 06.01.2016. Aftershocks or hidden nuclear tests?
Insight into the modeling of seismic waves for detection of underground cavities
MOX (The Laboratory for Modeling and Scientific Computing, Department of Mathematics) and at DICA (Department of Civil and Environmental Engineering) of the Politecnico di Milano（米兰理工大学数学系建模与科学计算实验室（MOX）和土木与环境工程系（DICA））
Response of the underground environment of the KAGRA observatory against the air-pressure disturbance from the Tonga volcano eruption on January 15th, 2022
