Abstract
The present paper reports the analysis of GPS based TEC measurement corresponding to 5 earthquakes (M > 6.0) that have occurred in 2009 and 2010 during low solar activity period and quiet geomagnetic conditions. The No. of satellites registering high TEC at low elevation angles is observed prior to these earthquakes. The earthquakes are 1) Loyalty Island (22o36'S, 170o54'E) M-6.6 on 19 January 2009, 2) Izu Island (32o48'N, 140o36'E) M-6.6 on 12 August 2009, 3) Ryukyu Islands (23o30'N, 123o30'E) M-6.7 on 17 August 2009, 4) Haiti (18o24'N, 72o30'W) M-7.0 on 12 Jan 2010, 5) Chile (34o12'S, 71o48'W) M-6.9 on 11 March 2010. To identify anomalous behavior of TEC, we compute interquartile range associated with median TEC so as to get upper and lower bound of TEC variation. The results show occurrence of anomalies in VTEC 1 - 13 days prior to the earthquake. The VTEC shows enhancement for all the earthquakes. Enhancement in No. of satellites registering high TEC at low elevation has been observed prior to earthquakes.
Highlights
Extensive researches have resulted in the recognition of many earthquake precursors in the field of the lithosphere, atmosphere and ionosphere
It is observed that prior to the earthquake on 19 January 2009 at Southeast of Loyalty Island there is an increase in Vertical TEC (VTEC) diurnal profile
1) It is observed that we find anomalous variation in total electron content (TEC) for all 5 earthquakes included in the paper, which is in agreement with those reported by earlier literature, and it can be observed that ionosphere behavior changes, a few days prior to a major seismic shock within or far from the earthquake preparatory zone
Summary
Extensive researches have resulted in the recognition of many earthquake precursors in the field of the lithosphere, atmosphere and ionosphere. The effect of pre-seismic activity on ionosphere can be investigated by using the ionosphere electron density. The variation of electron concentration related to earthquake has been reported by Ondoh [1] and Liperovsky et al [2]. Large scale ionospheric irregularity in the F-region is observed by many authors [3]-[6]. The electric field triggered by an earthquake preparatory process generates E × B drift. Depletion and enhancement in density profile may be a result of earthquake associated E × B drift [7]. GPS based total electron content (TEC) variation prior to an earthquake was observed by [8].
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