Seismo-Acoustic Energy Partitioning at Near-Source and Local Distances from the 2011 Sayarim Explosions in the Negev Desert, Israel

Abstract

The January 2011 calibration explosions at the Sayarim Military Range in the Negev Desert, Israel, provide a unique dataset to study seismic and acoustic partitioning for surface sources at near‐source and local distances. We present an analysis of the seismic and overpressure/acoustic signals generated from two explosions, which included 10,240 and 102,080 kg of mainly ANFO with some Composition B, detonated on the surface, on 24 and 26 January, respectively, at different times of the day. A temporary seismo‐acoustic‐overpressure network was deployed at distances between 0.1 and 39 km to supplement data from permanent stations in Israel. The near‐source data confirm the explosions produced overpressure signals consistent with complete and simultaneous surface detonation of 7.4 and 76.8 metric tons of TNT‐equivalent explosives. We observe acoustic amplification at local distances (>5 km) south of the larger explosion that can be explained by a low‐altitude southward flowing wind at the detonation time. For the smaller shot, the southward flow was not present and amplification was not observed in the pressure data. We present results of modeling these overpressure data with blast pressure scaling models with and without meteorological data. Seismic phases generated by the surface shots include P waves, fundamental and higher mode Rayleigh waves, and Love waves that appear to have been generated at or very near the explosion source. The seismic ground motion is less than would be expected for fully coupled explosions of 7.6 and 76.8 tons, and at near‐source distances (<10 km) can be modeled well by reducing ground‐motion predictions from the Fuis et al. (2001) model by a factor of 4. The results from the Sayarim explosions, combined with past and future experimental datasets, will lead to an improved understanding of the seismo‐acoustic source function for explosions and energy partitioning between seismic and acoustic waves.