Changes in total electron content associated with earthquakes (M > 5) observed from GPS station, Varanasi, India

Figures & data

Figure 1. Location of the Varanasi observation station (marked by a green star) and the locations of the epicentres (marked by red crosses) of the nine earthquakes analysed. Available in colour online.

Figure 2. Schematic diagrams showing the geometry of the configuration in the conversion of slant total electron content (STEC) to vertical total electron content (VTEC) from the ionospheric pierce point (IPP) at altitude h.

Table 1. Catalogue of the nine earthquakes analysed.

Serial no.	Place	Date	Time of main shock (UTC)	Latitude (°)	Longitude (°)	Distance (km)	Magnitude (M)	Precursor observed before (day)	Effect on ionospheric TEC (I: increase; D: decrease)
1	Myanmar (India)	30 July 2007	22:42:09.2	19.3 N	95.6 E	1457	5.9	1, 6	1–I, 6–D
2	China	9 January 2008	08:26:54.7	32.0 N	84.8 E	765	6.3	2, 5	2–I, 5–I
3	China	20 March 2008	22:32:55.7	35.8 N	81.8 E	1173	6.8	2, 3, 5	2–I, 3–D, 5–D
4	China	12 May 2008	06:27:56.4	30.5 N	104.2 E	2158	7.5	5	5–D
5	Tibet (India)	25 August 2008	13:21:57.0	30.9 N	83.6 E	625	6.4	3	3–D
6	Nepal	8 December 2008	08:59:07.0	29.9 N	82.1 E	519	5.7	2, 4, 5, 6	2–I, 4–D, 5–I, 6–D
7	Rajasthan (India)	9 April 2009	01:46:57.0	27.1 N	70.7 E	1243	5.3	2, 4, 5, 6	2–D, 4–D, 5–D, 6–D
8	Andaman	25 February 2010	03:51:47	14.4 N	93.1 E	1600	5.0	2, 4	2–D, 4–D
9	Myanmar	12 March 2010	23:19:54	23.0 N	94.5 E	1194	5.6	1, 2	1–D, 2–D

Figure 3. Variation in (a) total electron content (TEC), (b) Dst-index, (c) AE-index and (d) ap-index (15–25 March 2008) during the China earthquake (20 March 2008).

Figure 4. Variation in (a) total electron content (TEC), (b) Dst-index, (c) AE-index and (d) ap-index (3–15 April 2009) during the Jaisalmer Rajasthan earthquake (9 April 2009).

Figure 5. Variation in (a) total electron content (TEC), (b) Dst-index, (c) AE-index and (d) ap-index (24 Jul–5 August 2007) during the Myanmar earthquake (30 July 2007).

Figure 6. Block diagram showing the mechanism of seismo-ionospheric coupling.