GOCE: The first seismometer in orbit around the Earth

Abstract

[1] The first in situ sounding of a post-seismic infrasound wavefront is presented, using data from the GOCE mission. The atmospheric infrasounds following the great Tohoku earthquake (on 11 March 2011) induce variations of air density and vertical acceleration of the GOCE platform. These signals are detected at two positions along the GOCE orbit corresponding to a crossing and a doubling of the infrasonic wavefront created by seismic surface waves. Perturbations up to 11% of air density and 1.35 10 -7 m/s 2 of vertical acceleration are observed and modeled with two different solid-atmosphere coupling codes. These perturbations are a due to acoustic waves creating vertical velocities up to 130 m/s. Amplitudes and arrival times of these perturbations are reproduced respectively within a factor 2, and within a 60 s time window. Waveforms present a good agreement with observed data. The vertical acceleration to air density perturbation ratio is higher for these acoustic waves than for gravity waves. Combining these two pieces of information offers a new way to distinguish between these two wave types. This new type of data is a benchmark for the models of solid-atmosphere coupling. Amplitude and frequency content constrain the infrasound attenuation related to atmosphere viscosity and thermal conductivity. Observed time shifts between data and synthetics are ascribed to lateral variations of the seismic and atmospheric sound velocities and to the influence of atmospheric winds. These effects should be included in future modeling. This validation of our modeling tools allows to specify more precisely future observation projects.

Ionospheric response to infrasonic‐acoustic waves generated by natural hazard events

“…While acoustic waves presented in Figure 2 all have large wind velocities (> 80 m/s), direct measurements have revealed acoustic waves with velocities of ∼130 m/s [Garcia et al, 2013] following the Tohoku earthquake, even far from the epicenter. Moreover, qualitative comparison against TEC data in section 4 suggests that these acoustic waves have amplitudes consistent with those generated by realistic sources.…”

Thermospheric mass density: A review

“…In a study directly related to thermospheric density, R. F. Garcia et al (2013) used GOCE density measurements to detect infrasonic waves generated by the March 2011 Tohoku earthquake. The waves propagated from the source to the thermosphere in about 30 min, where they caused density perturbations of up to 11%.…”

All‐sky imaging of transglobal thermospheric gravity waves generated by the March 2011 Tohoku Earthquake

“…In the case of the Tohoku earthquake, perturbations of up to 11% were reported from in situ accelerometer measurements by the GOCE satellite located in earth orbit near 270 km altitude. The detections were obtained at two locations along its orbit: over the central Pacific and over northern Africa, approximately 3000 km and 11000 km from the epicenter, at 27 min and 56 min after the earthquake, respectively [ Garcia et al ., ].…”