Seismoacoustic analysis of the 7th July 2011 Abadan, Turkmenistan explosions.

Abstract:

At 16:40 (local time) on 7th July 2011, a series of explosions occurred in the town of Abadan, Turkmenistan. The Turkmenistan government listed the cause of the accident as the ignition of pyrotechnic matter intended for fireworks, which then spread to military storage areas, where an estimated 5,000 to 50,000 tons of ammunition was stored (Boggs et al., 2013). It was reported that shrapnel from these explosions was found 10 km away.

The explosions are clearly observed ~11 km away at the International Monitoring System (IMS) seismic array GEYT (Turkmenistan). A total of 30 individual events can be identified; the first detected explosion occurred at 16:51 and the final explosion at 17:21. Each event displays clear P-wave, Rg, and air-to-ground coupled arrivals. Yields are estimated from the amplitude of the P-wave arrivals (Koper et al., 2002) for each event and range between 1 – 45 tonnes. Yields are also estimated using the amplitude of the Rg arrival (Bonner and Russell, 2013) and range between 0.5 – 17 tonnes.

These explosions are also observed at three IMS infrasound arrays in Kazakhstan (1300km), Russia (2600 km), and Germany (3700 km). Individual explosions cannot be identified in these long-range recordings; signal dispersion combined with short inter-explosion intervals result in overlapping arrivals. Using the empirical relationship between the infrasonic signals dominant period and yield (e.g., Green et al., 2011) we are able to estimate a yield, for the largest explosion(s), of 20 tonnes. This is in close agreement with the yields estimated from seismic signals at local distance.

The observed air-to-ground coupled waves at each station exhibit downward first motions, consistent with an initial positive blast overpressure. We measure the period and peak-to-peak amplitude of the air-to-ground coupled waves and compare these to the P-wave and Rg estimated yields. We find a possible linear-relationship linking yield to the period of these observed air-to-ground coupled waves. The relationship between yield and peak-to-peak amplitude appears to be more complex.

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