Calibrating infrasonic to seismic coupling using the Stardust sample return capsule shockwave: Implications for seismic observations of meteors

Abstract

1] Shock waves produced by meteoroids are detectable by seismograph networks, but a lack of calibration has limited quantitative analysis of signal amplitudes. We report colocated seismic and infrasound observations from reentry of NASA's Stardust sample return capsule (SSRC) on 15 January 2006. The velocity of the SSRC (initially 12.5 km/s) was the highest ever for an artificial object, lying near the low end of the 11.2-72 km/s range typical of meteoroids. Our infrasonic/seismic recordings contain an initial N wave produced by the hypersonic shock front, followed $10 s later by an enigmatic series of weak, secondary pulses. The seismic signals also include an intervening dispersed wave train with the characteristics of an air-coupled Rayleigh wave. We determine an acoustic-seismic coupling coefficient of 7.3 ± 0.2 mm s À1 /Pa. This represents an energy admittance of 2.13 ± 0.15%, several orders of magnitude larger than previous estimates derived from earthquake or explosive analogs. Theoretical seismic response was computed using in situ V P and V S measurements, together with laboratory density measurements from samples of the clay-rich playa. Treatment of the air-ground interface as an idealized air-solid contact correctly predicts the initial pulse shape but underestimates its seismic amplitude by a factor of $2. Full-wave synthetic seismograms simulate the air-coupled Rayleigh wave and suggest that the secondary arrivals are higher-order Airy phases. Part of the infrasound signal appears to arise from coupling of ground motion into the air, much like earthquake-induced sounds.

Modeling propagation of infrasound signals observed by a dense seismic network

“…This estimate agrees well with the previous collocated infrasound/seismic observations of sonic booms (McDonald and Goforth, 1969), shock waves produced by NASA's Stardust sample return capsule (Edwards et al, 2007), thunderstorms (Usoltseva et al, 2012) and model estimates of the air-to-ground coupling (Ben-Menahem and Singh, 1981), which is ranging from 0.5 to 10 (lm/s)/Pa.…”

Frequency-Dependent Acoustic-Seismic Coupling of Meteor Shock Waves

“…Thus, according to theoretical predictions of acousticseismic coupling Singh, 1981, 2000), we anticipate that any observed coupling should be free of persistent wavetrains of air-coupled Rayleigh waves seen in other meteor-related seismic observations (e.g., Langston, 2004;D'Auria et al, 2006;Edwards, Eaton, et al, 2007), and appear as phase modified and scaled versions of the incident source wavelet. Additionally, we expect that a poorer coupling between the air and surface will exist at the site than would be the case if shear velocities were at or below acoustic sound speeds (Langston, 2004;Edwards et al, 2008).…”

“…Previous studies of acoustic-seismic coupling for high-velocity spacecraft using these relations have met with general success (to within a factor of 2 in amplitude) in reproducing observations when compared with the theoretical and measured source airwaves (Kanamori et al, 1992;Edwards, Eaton, et al, 2007). Singh (1981, 2000) approximate the air-surface interface as fluid and solid half spaces in contact (continuous vertical displacement and stress with shear stress in the solid vanishing at the interface).…”

“…Recently, Edwards, Eaton, et al (2007), using observations of the reentry of the NASA Stardust sample return capsule, concluded that a fluid-solid half space treatment of the atmosphere-surface interface (Ben-Menahem and Singh, 2000) permits calculation of the air-coupled shock wave amplitude to within a factor of 2, given adequate knowledge of the site's near-surface seismic velocities and bulk density. If such a treatment were robust, source-energy estimation for natural meteors might be possible through transformation of the seismic waveform into a pseudoacoustic wave, which could then be used to estimate meteor energy using well established infrasonic methods (Edwards et al, 2006).…”

Infrasound/seismic observation of the Hayabusa reentry: Observations and preliminary results

“…Following the reentries of the Genesis in (ReVelle et al, 2005Jenniskens et al, 2006) and the Stardust in 2006 (Edwards et al, 2007), the return of the Hayabusa Sample Return Capsule (H-SRC) was the third direct reentry event from the interplanetary transfer orbit to the Earth at a velocity of over 11.2 km/s. In addition, it was the world's rst case of a direct reentry of the spacecraft (H-S/C) itself from the interplanetary transfer orbit.…”