Is there a one-to-one correspondence between ionospheric anomalies and large earthquakes along Longmenshan faults?

Abstract

On 12 May 2008, a destructive M8.0 earthquake struck Wenchuan County (31.0 N, 103.4E) in the Longmenshan fault zone of southwestern China. Five years later, on 20 April 2013, another terrible M7.0 earthquake struck Lushan County (30.3 N, 103.0 E) in the same fault area, only 87 km away from the epicenter of the Wenchuan earthquake. In this paper, an integrated wavelet analysis methodology is proposed to detect and diagnose ionospheric total electron content (TEC) anomalies related to seismic activities. Analytic wavelet transform is used to detect ionospheric perturbations, and then cross-wavelet analysis is used to diagnose ionospheric anomalies by gaining further insights into the dynamic relationship between the anomaly variability of ionospheric TEC and geomagnetic indices for the same set of observations. The results show that a significant ionospheric disturbance occurred on 9 May 2008 above the forthcoming epicenter, 3 days prior to the Wenchuan earthquake. However,we did not observe an ionospheric anomaly over the epicenter of the Ya’an earthquake during the 1 month period before the shock. Finally, we discuss the possible interpretations of the different seismo-ionospheric effects for the two similar earthquakes.