# Detection of Electromagnetic Seismic Precursors from Swarm Data by Enhanced Martingale Analytics
## 4 Quantitative Experiment
### Greece 2020
#### 4.2.2 \(1000\times 800\) km  
Figure 11 showcases the EMF intensity activity across a \(1000\times 800\) km area before and after the seismic event. Each data point represents the mean intensity value per day, calculated using Equation (10). The figure consists of two sub-figures (as in Section 4.2.1): Figure 10(a),b. In Figure 10(a), the unmodified time-series obtained from the \(1000\times 800\) km grid is depicted. It is noticeable that approximately 1 year prior to the event date, the values obtained for Beta exhibit errors, showing zero values for \(b_{x}\), \(b_{y}\), and \(b_{z}\). To enhance visual  
Figure 10: Plots of the time-series produced from Alpha, Beta, and Charlie satellites with intensity values obtained from a \(500\times 300\) km grid centered on the epicenter of the 2020 Greek earthquake. The color coding is Alpha (red), Beta (green), and Charlie (blue). (**a**) An unmodified plot of the time-series produced from Alpha, Beta, and Charlie over a \(500\times 300\) km grid centered on the epicenter of the 2020 Greek Earthquake. It is clear that the results of Beta inhibit our ability to visually explore the plot with ease, so we provide (**b**) with Beta removed to highlight the behaviors of Alpha and Charlie. (**b**) A modified plot of the time-series produced from Alpha and Charlie over a \(500\times 300\) km grid centered on the epicenter of the 2020 Greek Earthquake. Beta has been removed from the plot to enhance our visual interpretations but is observable in (**b**). clarity, Figure 11b displays only the time-series of Alpha and Charlie. It is important to highlight that, as in Section 4.2.1, though we modified the plot in Figure 11b to exclude Beta, we did not exclude Beta from our analysis. Figure 9 shows the results from both the Martingale and \(z\)-Martingale systems operating over the data shown in Figure 11a. Figure 9a shows the results obtained from the original Martingale system. Alpha, Beta, and Charlie allow the production of anomalies within their respective time-series. Alpha exhibits a group of anomalies approximately 10 months prior to the seismic event date followed by anomalies immediately preceding  
Figure 11: Plots of the time-series produced from Alpha, Beta, and Charlie satellites with intensity values obtained from a \(1000\times 800\) km grid centered on the epicenter of the 2020 Greek earthquake. The color coding is Alpha (red), Beta (green), and Charlie (blue). (**a**) An unmodified plot of the time-series produced from Alpha, Beta, and Charlie over a \(1000\times 800\) km grid centered on the epicenter of the 2020 Greek Earthquake. It is clear that the results of Beta inhibit our ability to visually explore the plot with ease, so we provide (**b**) with Beta removed to highlight the behaviors of Alpha and Charlie. (**b**) A modified plot of the time-series produced from Alpha and Charlie over a \(1000\times 800\) km grid centered on the epicenter of the 2020 Greek Earthquake. Beta has been removed from the plot to enhance our visual interpretations but is observable in (**a**). and on the event date. Beta exhibits anomalies at approximately 9 months prior to the event date with no further detection afterwards. Charlie's time series results in several anomalies between the 9 month and 6 month periods of time without any further reports. Figure 8(b) shows the results obtained from processing the data of Alpha, Beta, and Charlie with our \(z\)-Martingale approach. Alpha follows a similar pattern of detected anomalies as in Figure 8(a), though with larger visible spikes. Beta exhibits a similar behavior as in Figure 8(a), though more anomalies are produced and several spikes show significant increases in their magnitudes. Charlie follows the pattern exhibited by Figure 8(a) very closely, with anomalies detected at approximately the same time; interestingly, as with Alpha and Beta, we see distinctive change in the magnitude of spikes within Charlie.