Ionospheric anomaly at the occurring time of China’s May 12, 2008, M = 7.9 Wenchuan Earthquake using nonlinear principal component analyses and image decoding

Nonlinear principal component analysis (NLPCA) and image decoding are used to determine the spatial pattern of a total electron content (TEC) map anomaly in the ionosphere above China’s Wenchuan earthquake of 12 May, 2008 (UT) (Mw = 7.9). The earthquake occurred at 06:28:01UT and the time period examined using NLPCA is 06:00 to 08:00UT. The TEC map of previous time period is transformed to an input matrix of NLPCA using image decoding, and then the TEC anomaly found is widespread and less intense at an altitude of 200 km using NLPCA; however, it becomes more intense and localized with height up to an altitude of 300 km. This paper discusses potential causes of the anomaly with emphasis on very rising acoustic shockwaves and snow-plow effects on ionospheric electron plasma resulting from the mainshock of the earthquake.