# Detection of Geomagnetic Signals as Precursors to Some Earthquakes in China
## 3 Polarization Results and Earthquakes
### Polarization Results of the Jinta Earthquake  
An \(M_{\rm s}\) 5.4 earthquake occurred on 3 May 2012 at 02:19 UT in Jinta Inner Mongolia, China. The earthquake focal depth was 8 km and most closely located (about 100 km) to the JYG observatory in western China (Figure 1c). The resistivity of the hypocenter is approximately 10 \(\Omega\cdot\)m, the magnetic permeability is approximately 4\(\pi\)\(\times\)\(10^{-7}\) (H/m), and the depth is 8 km. According to the Equation (3), the possible seismic-electromagnetic emission frequency originating from the earthquake source was about 0.04 Hz. The polarization \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Date** & **Lon/o** & **Lat/o** & **Epicenter** & **Magnitude/\(M_{\rm s}\)** & **Depth/km** & **Station** & **Distance/km** \\ \hline
18 June 2008 & 91.20 & 35.30 & Zhiduo & 5.4 & 10 & GLM & 360 \\
13 October 2008 & 73.90 & 39.50 & Tajikistan & 5.3 & 8 & KSH & 164 \\
10 November 2008 & 95.90 & 37.60 & Haixi & 6.3 & 10 & GLM & 140 \\
20 February 2009 & 78.60 & 40.80 & Aheqi & 5.2 & 13 & KSH & 249 \\
19 April 2009 & 78.30 & 41.30 & Aheqi & 5.4 & 30 & KSH & 290 \\
22 April 2009 & 77.30 & 40.10 & Artush & 5.0 & 25 & KSH & 140 \\
28 August 2009 & 95.90 & 37.60 & Haixi & 6.6 & 10 & GLM & 160 \\
7 September 2010 & 73.90 & 39.50 & Uqia & 5.5 & 30 & KSH & 300 \\
11 August 2011 & 77.20 & 39.90 & Artush & 5.8 & 10 & KSH & 127 \\
1 December 2011 & 77.00 & 38.40 & Shache & 5.0 & 30 & KSH & 160 \\
9 March 2012 & 81.40 & 39.50 & Luopu & 5.9 & 30 & KSH & 480 \\
3 May 2012 & 98.60 & 40.60 & Jita & 5.4 & 8 & JYG & 100 \\
31 May 2012 & 78.82 & 43.52 & Kazakhstan & 5.9 & 8 & KSH & 520 \\
1 June 2012 & 75.10 & 39.90 & Uqia & 5.0 & 7 & KSH & 75 \\
11 August 2012 & 78.20 & 40.00 & Artush & 5.2 & 9 & KSH & 210 \\
29 January 2013 & 79.70 & 42.60 & Kazakhstan & 6.1 & 20 & KSH & 480 \\
30 January 2013 & 94.70 & 32.90 & Zaduo & 5.1 & 20 & GLM & 390 \\
12 February 2013 & 92.40 & 38.50 & Haixi & 5.1 & 10 & GLM & 320 \\
11 March 2013 & 77.50 & 40.20 & Artush & 5.2 & 8 & KSH & 165 \\
5 June 2013 & 95.88 & 37.58 & Haixi & 5.0 & 4 & GLM & 155 \\
30 June 2013 & 73.41 & 39.22 & Tajikistan & 5.0 & 10 & KSH & 209 \\
23 November 2013 & 75.71 & 42.53 & Kazakhstan & 5.2 & 9 & KSH & 340 \\
21 October 2013 & 76.90 & 35.30 & Kashmir & 5.5 & 30 & KSH & 470 \\
23 November 2013 & 75.71 & 42.53 & Kyrgyzstan & 5.2 & 9 & KSH & 340 \\
1 December 2013 & 78.98 & 40.26 & Keping & 5.3 & 9 & KSH & 280 \\
9 July 2014 & 78.27 & 39.31 & Maigaiti & 5.1 & 8 & KSH & 220 \\
14 November 2014 & 77.27 & 42.16 & Kyrgyzstan & 5.7 & 10 & KSH & 330 \\
10 January 2015 & 77.27 & 40.21 & Artush & 5.0 & 10 & KSH & 150 \\
3 July 2015 & 78.20 & 37.60 & Pishan & 6.5 & 10 & KSH & 300 \\
18 November 2015 & 73.04 & 40.38 & Kyrgyzstan & 6.0 & 7 & KSH & 256 \\
7 December 2015 & 72.90 & 38.20 & Tajikistan & 7.4 & 30 & KSH & 291 \\
26 June 2016 & 73.40 & 39.43 & Kyrgyzstan & 6.7 & 10 & KSH & 207 \\
17 October 2016 & 94.93 & 32.81 & Zaduo & 6.2 & 9 & GLM & 400 \\
25 November 2016 & 74.04 & 39.27 & Aketao & 6.7 & 10 & KSH & 155 \\
3 May 2017 & 71.58 & 39.42 & Tajikistan & 6.2 & 30 & KSH & 380 \\
5 May 2017 & 71.50 & 39.45 & Tajikistan & 6.0 & 20 & KSH & 380 \\
11 May 2017 & 75.25 & 37.58 & Taxkorgan & 5.5 & 8 & KSH & 220 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Information of earthquakes and stations. ratios of \(Y_{\rm ZH}\) and \(Y_{\rm ZG}\) of the geomagnetic data within the frequency range of 0.04 Hz in the JYG station were thus obtained. Figure 2a,b illustrate the temporal evolution of the \(Y_{\rm ZH}\) and \(Y_{\rm ZG}\) during 2011-2012. A five-day moving average was used in all calculation results in the plot. A vertical arrow indicates the earthquake occurrence date (3 May 2012). The red dotted line represents the threshold value of \(m+2\sigma\), where \(m\) is the mean value of polarization ratio over the entire period and \(\sigma\) is the standard deviation. Some significant enhancements of \(Y_{\rm ZH}\) started on 29 April 2012, and ended on 27 June 2012.