Recovering noise correlation function from GNSS-derived total electron content

Total electron content (TEC) measured by Global Navigation Satellite System (GNSS) receivers has been shown to be useful for remote-sensing of Earth surface motion. This is especially true for areas on Earth where installation of seismometers is cost prohibitive, such as the oceans. Seismic methods such as ray tracing, beamforming, and back projection have been used to localize surface-rupturing earthquake events. This study investigates the potential application of seismic interferometry to GNSS-derived TEC time series data. Specifically, we investigate whether it is possible to obtain a useful noise correlation function for the TEC after a surface-rupturing earthquake. The implementation of interferometry here is complicated by the nature of the data (measurement along the line of sight), as well as the motion of the GNSS satellites. Naughton et al. (2016, doi:10.1121/1.4971172) showed that it is possible to recover the noise correlation function from free-floating oceanic receivers when certain parameters are carefully chosen. These parameters include the bandwidth and time window, with the latter being dependent on the velocity and relative change in distance between stations. Here we look at how the physics of the ionosphere influences these parameters and compare results of cross correlations of TEC with calculated travel times. Successful retrieval of the noise correlation function could yield an estimate of the Green function between two points in the ionosphere.

Permission to publish was granted by Director, Geotechnical & Structures Laboratory.

REFERENCES

Naughton, P., Roux, P., Yeakle, R., Schurgers, C., Kastner, R., Jaffe, J. S., & Roberts, P. L. D. (2016). Ambient noise correlations on a mobile, deformable array. Journal of the Acoustical Society of America, 140(6), 4260-4270. doi:10.1121/1.4971172