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Is an unusual large enhancement of ionospheric electron density linked with the 2008 great Wenchuan earthquake?

“…[2] Recently, there are growing interests in studying the presence of ionospheric anomalies prior to earthquakes [Pulinets and Boyarchuk, 2004]. Both ground-based ionosonde data [e.g., Ondoh and Hayakawa, 1999;Liu et al, 2000;Chuo et al, 2002;Popov et al, 2004;Liperovskaya et al, 2006;Dabas et al, 2007] and topside sounding observations [Pulinets and Legen'ka, 2003] have shown that ionospheric variations associated with the seismic activity do exist, a few days or hours prior to the seismic shocks of large intensity (M > 5). One of the problems to identify ionospheric precursors is that the sign of the deviations of the ionospheric parameters, usually represented by critical frequency of F 2 layer ( f o F 2 ), total electron content (TEC) and sporadic E layers ( f o Es), differs from case to case.…”

“…[3] Spatial distribution of ionospheric precursors can be obtained by two-dimensional map technique through the combination of the data from topside sounding and groundbased ionospheric stations as well as GPS network [Liu et al, 2001;Pulinets and Legen'ka, 2003;Zakharenkova et al, 2008]. Previous studies show that the maximum of the affected area in the ionosphere does not coincide with the vertical projection of the epicenter of the future earthquake and shifted equatorward in high and middle latitudes.…”

Anomalous enhancement of ionospheric F2 layer critical frequency and total electron content over low latitudes before three recent major earthquakes in China

“…In recent years, coupling between the dynamics of lithospheric processes and ionospheric anomalies prior to earthquakes is of growing interest. Both ground-based ionosonde observations [Ondoh and Hayakawa, 1999;Liu et al, 2000;Chuo et al, 2002;Popov et al, 2004;Liperovskaya et al, 2006;Dabas et al, 2007;Dutta et al, 2007;Sharma et al, 2008] and topside sounding observations [Gokhberg et al, 1983;Pulinets and Legen'ka, 2003] have shown that ionospheric variations associated with seismic activity do exist, and appear as precursory effects a few days to a few weeks before an earthquake of large intensity (M > 6). A wide class of ionospheric anomalies can be observed in plasma density, temperature, and composition.…”

Nonlinear principal component analysis in the detection of ionospheric electron content anomalies related to a deep earthquake (>300 km, M 7.0) on 1 January 2012, Izu Islands, Japan

“…[20] The other possibility is the presence of an electric field creating large scale ionospheric density irregularities either from radon gas release and P-type semiconductor effects due to stress variance in rocks near the focus of the earthquake [Liu et al, 2004;Pulinets and Legen'ka, 2003;Pulinets, 2004;Freund, 2003;Lin, 2012]. As mentioned in the introduction, much pre-earthquake research has pointed to shallow earthquakes being associated with recognized TEC anomalies [Le et al, 2011], although Pulinets thought that large deep earthquakes could provide the necessary preparation zone to create the 200 km diameter lower atmosphere electric field necessary for ionospheric disturbance.…”