Adaptive techniques for extraction of pre-seismic parameters of Total Electron Content (TEC) at anomaly crest station

Figures & data

Figure 1. Relationship between TEC_peak and Kp during (a) a low solar activity period (2009, Rz = 2.0) and (b) a high solar activity period (1981, Rz = 143.0).1 TECU = 10¹⁶ el m⁻².

Figure 2. Day-to-day variation in TEC_peak for February 2006. Here days of possible earthquakes identified by us are shown by red rectangles

. Low latitude earthquake occurrence days are marked by symbol • for M> 5 and ˆ for M< 5. The numbers 1, 2, 3 and 4, given below the rectangles, highlight the association of a low latitude earthquake event and our identified possible earthquake day. The Q-day Sd limits (thick lines) are also shown. 1 TECU = 10¹⁶ el m⁻².

Figure 3. TEC profile shape for high solar activity period for a quiet day on 14 June 1980 and for a disturbed day on 2 February 1981. 1 TECU = 10¹⁶ el m⁻².

Figure 4. TEC profile shape at a low solar activity period for 24 November 2008 (red curve) with Kp = 0 and for 26 November 2008 (green curve) with Kp = 13. 1 TECU = 10¹⁶ el m⁻².

Figure 5. Superimposition of a number of TEC profiles covering pre-earthquake to earthquake days for examining modifications in TEC profile shape by the earthquake preparatory process. Earthquake event shown in the figure is for 12 August 2009. 1 TECU = 10¹⁶ el m⁻².

Table 1. Earthquake epicentres and magnitudes of the cases analysed with the Dynamic Time Warping (DTW) technique. The days for which total electron content (TEC) profiles are used for construction of a template are shown. Kp values for the respective day are also presented.

Date of earthquake			Group of Q-days with Kp values for construction of the template
event	Epicentre	Magnitude	Date	Kp values
21/09/2009	27.32° N, 91.42° E 20.39°N, 94.77° E	6.1 5.7	10/09/2010	0
			11/09/2010	1
			12/09/2010	1
			13/09/2010	2
			14/09/2010	1
			15/09/2010	1
02/03/2006 03/03/2006	24°.27'N, 94°. 53' E 21°. 12'N, 94°.47' E	4.9 5.2	09/02/2006	1
			10/02/2006	3
			23/02/2006	4
			24/02/2006	2
			25/02/2006	0
12/05/2008	31° 24' N, 103° 58' E	7.9	29/04/2008	3
			30/04/2008	5
			01/05/2008	8
			02/05/2008	13
			03/05/2008	13
			04/05/2008	9

Figure 6. TEC profile for (a) a Q-day (representative case) and (b) a pre-earthquake day of 20 September 2009. An earthquake occurred on 21 September 2009. 1 TECU = 10¹⁶ el m⁻².

Figure 7. ‘Certainty factor’ for the month of September 2009. Note the drop in this factor during the earthquake event, which occurred on 21 September 2009.

Figure 8. Identification of earthquake days by (a) TEC_peak variations, (1 TECU = 10¹⁶ el m⁻²) and (b) DTW technique with ‘certainty factor’ for events of 2 March 2006 and 3 March 2006. The circles in the figures mark the earthquake days.

Figure 9. ‘Certainty factor’ calculated by the DTW method for May 2008. Note the dip in the ‘certainty factor’ prior to the 12 May 2008 earthquake, marked by an arrowhead. The post earthquake anomaly in the ‘certainty factor’ is likely to be associated with strong aftershocks.