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Abstract
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. [Citation2008, 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.
Acknowledgements
The author is grateful to: Dr. J.Y. Liu and Dr. C.C. Hsiao of the Institute of Space Science, Dr. Louis (L.Y.) Tsai of the Graduate Institute of Applied Geology and Dr. H.W. Chen of the Institute of Geophysics, National Central University for their useful references and data support. Special gratitude is extended to the author's German professors, Dr. Jürgen Fertig and Andreas Weller of the Institute of Geophysics, Technische Universität Clausthal for my training in Germany. I would also like to thank the anonymous reviewers for their valuable comments and suggestions. Finally, I would like to thank Dan Flynn of www.planetediting.com for the English editing.