Statistical analysis of fireballs: Seismic signature survey

TL;DR

This study analyzes seismic data to detect fireballs, revealing that seismic sensors can identify a significant portion of fireball events within 200 km, and suggests expanding seismic monitoring for better detection.

Contribution

First seismic bulk analysis of a large fireball dataset, demonstrating seismic detection potential and factors influencing fireball identification in seismic records.

Findings

25 fireballs detected in seismic data, representing 1.8% of surveyed fireballs.

Seismic peaks align with expected arrival times of shock waves from fireballs.

Detection likelihood depends on fireball energy, entry angle, and seismic sensor sensitivity.

Abstract

Fireballs are infrequently recorded by seismic sensors on the ground. If recorded, they are usually reported as one-off events. This study is the first seismic bulk analysis of the largest single fireball data set, observed by the Desert Fireball Network (DFN) in Australia in the period 2014-2019. The DFN typically observes fireballs from cm-m scale impactors. We identified 25 fireballs in seismic time series data recorded by the Australian National Seismograph Network (ANSN). This corresponds to 1.8% of surveyed fireballs, at the kinetic energy range of 10$^6$ to 10$^{10}$ J. The peaks observed in the seismic time series data were consistent with calculated arrival times of the direct airwave or ground-coupled Rayleigh wave caused by shock waves by the fireball in the atmosphere (either due to fragmentation or the passage of the Mach cone). Our work suggests that identification of fireball events in the seismic time series data depends both on physical properties of a fireball (such as fireball energy and entry angle in the atmosphere) and the sensitivity of a seismic instrument. This work suggests that fireballs are likely detectable within 200 km direct air distance between a fireball and seismic station, for sensors used in the ANSN. If each DFN observatory had been accompanied by a seismic sensor of similar sensitivity, 50% of surveyed fireballs could have been detected. These statistics justify the future consideration of expanding the DFN camera network into the seismic domain.