M. Tahir1
1ISTerre, Grenoble, France, and Yonsei University, Republic of Korea
Abstract:
Seismic moment tensors are a summation of force couples that are scale invariant, symmetric and independent of the coordinate system used to describe the source. Seismic moment tensors for certain types of source, such as volcanic earthquakes and nuclear explosions, are expected to contain an isotropic component and have volume change, whereas for a double couple, deviatoric tensor is maximum and no volumetric changes occur. In recent analysis we explore new methodology of regional moment tensor inversion to improve earthquake-explosion discrimination. Source parameters of India, Pakistan and North Korea nuclear explosions are determined and compared with those of earthquakes occurring in their vicinity. We observed maximum isotropic components (> 50%) during an explosion compared with the double couple component. A minor impression of double couple mechanism in the nuclear explosion may be due to the interactions of tectonic activity and multiple scattering. Moment magnitude of India (Mw 4.63) and Pakistan (Mw 4.57) explosions are comparable. North Korean explosion moment magnitudes for 2006 (Mw 4.03), 2009 (Mw 4.29), 2013 (Mw 4.47), 2016 (4.59, 5.65) were different and the 2016 North Korea is large compared to previous ones. Moment tensor inversions could be a vital tool for nuclear monitoring and event discrimination.
