Spatial pattern of a seismo-ionospheric signature using principal component analysis.

This article uses principal component analysis (PCA) to determine the spatial pattern of total electron content (TEC) anomalies in the ionosphere corresponding to China's Wenchuan Earthquake of 12 May 2008 UTC (Mw = 7.9). PCA is applied to global ionospheric maps (GIMs) with transforms conducted for the time period from 08:00 to 10:00 UT on 9 May 2008. The GIMs are subdivided into 100 smaller maps (36° longitude and 18° latitude). The smaller maps (71 × 71 pixels) form the transform matrices of corresponding dimensions (2 × 1) through image processing. The transform allows for extreme principal eigenvalues to be assigned to the seismo-ionospheric signature described by Zhao et al. [2008, Is an unusual large enhancement of ionospheric electron density linked with the 2008 great Wenchuan earthquake? Journal of Geophysical Research, 113, A11304, doi: 10.1029/2008JA013613.]. Results show that the range of the TEC anomaly declines with height; however, the anomaly becomes more localized and intense at higher altitudes (250–300 km), giving the anomaly the spatial pattern of a downward-facing trumpet. [ABSTRACT FROM AUTHOR]