Robert E. Reinke

Partitioning of Seismoacoustic Energy and Estimation of Yield and Height‐of‐Burst/Depth‐of‐Burial for Near‐Surface Explosions

Explosions near the Earths surface excite both seismic ground motions and atmospheric overpressure. The energy transferred to the ground and atmosphere from a near-surface explosion depends on yield (W) as well as the height-of-burst/ depth-of-burial(HOB/DOB)forabove/belowgroundemplacements.Wereportanalyses of seismic and overpressure motions from the Humble Redwood series of low-yield, near-surface chemical explosions with the aim of developing quantitative models of energy partitioning and a methodology to estimate W and HOB/DOB. The effects of yield, HOB, and range on amplitudes can be cast into separable functions of range andHOBscaledbyyield.WefindthatdisplacementoftheinitialPwaveandtheintegral of the positive overpressure (impulse) are diagnostic of W and HOB with minimal scat- ter. An empirical model describing the dependence of seismic and air-blast measure- ments on W, HOB/DOB, and range is determined and model parameters are found by regression. We find seismic amplitudes for explosions of a given yield emplaced at or above the surface are reduced by a factor of 3 relative to fully contained explosions below ground. Air-blast overpressure is reduced more dramatically, with impulse reduced by a factor of 100 for deeply buried explosions relative to surface blasts. Oursignalmodelsare usedtoinvertseismicandoverpressure measurementsforW and HOB and we find good agreement (W errors <30%, HOB within meters) with ground- truth values for four noncircular validation tests. Although there is a trade-off between W and HOB for a single seismic or overpressure measurement, the use of both meas- urement types allows us tolargelybreak this trade-off and better constrainW and HOB. However, both models lack resolution of HOB for aboveground explosions.