Source Localization of the 1991–1992 Southern California "Mystery Booms" from the SCSN Triggered Archive, Tested Against Space Shuttle and SR-71 Overflights

Robert L. Walker

Submitted August 30, 2026, SCEC Contribution #15552, 2026 SCEC Annual Meeting Poster #144

The pre-1999 SCSN triggered waveform archive contains an unexploited record of atmospheric acoustic sources. We revisit the 1991–1992 "mystery boom" series — recurring Thursday-morning sonic booms analyzed by Cates and Sturtevant (JASA 111, 614–628, 2002), who identified indirect booms from offshore operations but left the source-localization inverse problem open. From absolute-time burst catalogs spanning the CUSP triggered segments and continuous TERRAscope broadband, with consensus-based joint association of arrivals into three wavefronts, we localize the October 31, 1991 event to the outer Southern California Bight: a moving-source path model collapses the three fronts, spaced ~84 s, to a fixed illumination point at 33.42°N, 119.89°W, with ±40 km systematic range uncertainty along the ~250° azimuth. The fixed point and near-constant spacing favor discrete sources in trail over a common waypoint; range-dependent multi-skip returns of fewer sources are disfavored but not excluded by the trigger-censored data. A same-morning Vandenberg radiosonde rules out a tropospheric duct, consistent with stratospheric return. The estimators are tested on two documented trajectories in the same archive: the STS-55 reentry (May 6, 1993), whose terminal approach into Edwards is recovered from a small direct-carpet subset, and an SR-71 pass (December 8, 1993), where curated arrivals recover the documented east-to-west track within ~6° and segment speed within 15% of the published Mach 3.15. A complete 1989–1995 census identifies archived boom records from three further shuttle reentries, documents earthquake-contamination modes, and reveals a candidate series occurrence on November 3, 1994, two years after the published record ends.

Citation
Walker, R. L. (2026, 08). Source Localization of the 1991–1992 Southern California "Mystery Booms" from the SCSN Triggered Archive, Tested Against Space Shuttle and SR-71 Overflights. Poster Presentation at 2026 SCEC Annual Meeting.

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Seismology