Outline 1.Motivation 2.Global seismic monitoring: IMS 3.Global seismicity: IDC view 4.Global cross correlation grid: a design 5.Cross correlation at teleseismic distances 6.Underground nuclear explosions as master events 7.Synthetic master events 8.Principal and Independent Component Analysis 9.Testing with world seismicity of February 12, 2013 10. DPRK 2013 of February 12, 2013