Analysis of the November 1999 Dead Sea Calibration Shots
LAWRENCE LIVERMORE NATIONAL LAB CA
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In November 1999 three chemical explosions were conducted in the Dead Sea for the purposes of calibrating the International Monitoring System IMS for the Comprehensive Nuclear-Test-Ban Treaty CTBT. These shots were organized and conducted by the Geophysical Institute of Israel GII. Large chemical explosions are the most valuable form of ground truth as the location, depth and origin time are very well known. We focus on the two largest shots MW 3.6 and performed several types of analysis of the regional recordings and travel times of these shots. These data provide valuable new information about the region and offer an opportunity to test monitoring strategies. 1 A crustal and uppermost mantle velocity model was inferred from the travel times of the regional phases Pn, Pg and Sg. This effort utilized a grid search method to find suitable models of the structure. Results indicate that the crust is relatively thin 32 km with lower than average crustal velocities mean VP 6.1-6.2 kms. 2 We located each shot treating the other shot as a calibration explosion. Locations were computed using both station static corrections and kriged correction surfaces. Results show that the locations with static corrections can be better or worse than the locations without corrections. However, the locations with kriged correction surfaces are consistently better than those without corrections or with static corrections because kriging properly accounts for residual statistics. 3 Measures of the S-wave coda for regional events provide a stable estimate of event size moment magnitude, MW and the event source spectrum. S-wave coda envelope amplitudes were calibrated to moments estimated from long-period waveform modeling. We measured moment and body-wave magnitudes and source spectra for many events in the region. The Dead Sea shots show spectral peaking associated with shallow events.
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