Dichotomy in mode propagation of coseismic ionospheric disturbance: Observations from April 11, 2012 Indian Ocean earthquake
by Catherine, J. K., M. S. M. Vijayan, U. B. Syeda Rabiya, K. Shimna, V. K. Gahalaut, and D. S. Ramesh
The ionosphere response to the great intraplate Indian Ocean earthquake of April 11, 2012 (Mw 8.6) and its largest aftershock (Mw 8.2), is analysed using GPS aided Total Electron Content (TEC) measurements. Data from the dense GPS networks, SuGAR (Sumatran GPS Array) and the permanent Andaman-Nicobar array, formed the near-field observations at distances 250–1200 km from the epicenter. Stations such as IISC, DGAR and few others provided measurements over 2000 km from the epicenter. The CIDs with a propagation velocity of 930–1262 m/s, equal the speeds of the shock acoustic waves, arrive within 10–18 min after the earthquake occurrence. The observed phenomenon of CID splitting into two modes, north and south of the epicenter is akin to the well documented effects of anisotropy on wave propagation. Closer to the epicenter, to its south, the propagation velocity of CID is ~1 km/sec and further south east of the network the velocity reduces to 500–600 m/s. In contrast, towards Andaman in the north, the CID propagation velocity increases to 2–3.5 km/s. The zenith angle of the line-of-sight between the GPS receiver and satellite appears to influences the amplitude of the TEC fluctuations. The anomalous azimuthal variation of the Rayleigh wave radiation pattern best explains the observed N-S asymmetry of CID.
2015), Dichotomy in mode propagation of coseismic ionospheric disturbance: Observations from April 11, 2012 Indian Ocean earthquake., J. Geophys. Res. Space Physics, 120, doi:10.1002/2014JA020621., , , , , and (