Ionospheric perturbations observed by the GPS following the December 26th, 2004 Sumatra-Andaman earthquake

Using the Total Electron Content (TEC) data recorded by the GPS receiver network, installed under the GPS and Geo Augmented Navigation (GAGAN) program, ionospheric electron content on the day of the great Sumatra-Andaman earthquake of December 26, 2004 was examined. A significant perturbation of 1.5 to 2 TEC units over a smooth variation of TEC in the morning hours was observed within 45 minutes of the quake at stations situated near the east coast of the Indian subcontinent. The disturbance was found to propagate northwestward with its origin situated about 2 degrees northeast of the quake epicenter. Possible coupling mechanism of the crustal movement and the ionosphere are discussed.