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Seismo-Acoustic Yield Determination of the 4 August 2020 Beirut Explosion

Session: Analyses and Implications of the 4 August 2020 Beirut Explosion Series I

Type: Oral

Date: 4/22/2021

Presentation Time: 02:30 PM Pacific

Description: 

The 4 August 2020 Beirut explosion of ammonium nitrate produced multi-phenomenological signals (seismic, acoustic and hydroacoustic) that were well recorded at local and regional distances. The clear seismic signals allowed us to perform a seismic yield determination with waveform envelopes, a method which we have developed and refined over the past decade (Pasyanos et al., 2012). The method calculates synthetic waveform envelopes by propagating an earthquake or explosion source out to recording stations by accounting for geometrical spreading, attenuation, local site effects, and coda decay. Source parameters can then be estimated by minimizing the misfit between the observed waveform envelopes and the synthetic envelopes for a range of yields and depths. The misfit analysis is estimated for multiple frequency bands and potentially multiple stations. While the solid earth structure is well-known for this analysis, one major source of uncertainty is the material properties beneath the explosion.

Infrasound signals recorded on regional arrays have also allowed us to make an acoustic yield determination. In this method, transmission loss of acoustic energy is calculated by 2-D finite-difference method including a range-dependent weather specification and used to invert for explosion energy near the source. The yield is determined by the inverted explosion energy and an acoustic source model for chemical explosions (Kim et al., 2020). In contrast to the seismic analysis, a major source of uncertainty is the atmospheric conditions. We attempt to quantify the atmospheric variability by using stochastic realization. While estimates made using both methods have uncertainties that are not insignificant, combining the results can reduce the overall range of acceptable yields, which includes the likely true explosive yield. In both yield estimation methods, we are sensitive to energy partitioning at the earth-air-water interface, but this event should provide insight into the details of this coupling.

Presenting Author: Michael E. Pasyanos

Student Presenter: No

Authors