Indian explosions of 11 May 1998: An analysis of global seismic bodywave magnitude estimates

摘要

Seismic waves generated by the Indian explosions of 11 May 1998, showed large variations in the globally estimated body wave magnitudes (nt,), The estimated m(b) values were in general smaller at the stations in east and west directions with respect to these sources than in the. north direction. Synthetic seismograms demonstrate that such pattern is due to the cancellation and superposition of signals from these explosions separated in space by about 1 km, In view of this, the average m(b) estimates of the International Data Center cmc) at Arlington, USA (m(b) = 5.0) and the US Geological Survey (m(b) = 5.2) are smaller than the true m(b) value. After taking into account the necessary corrections, a value of m(b) = 5.39 is obtained as the global average. Gauribidanur array (GBA) seismogram showed anomalous PP/P amplitude ratio. After correcting for this anomaly, an estimate of m(b) = 5.4 is obtained at GBA, The revised in, estimate gives an average combined yield of 58 +/- 5 kt. [References: 17]