# Machine Learning-Based Precursor Detection Using Seismic Multi-Parameter Data
## 3 Results
### Multi-Parameter Relevancy Spectrum Calculation
On 19 March 2021, the Xizang Biru \(M_{\rm L}6.4\) earthquake occurred in the study area, proving that the extrapolation effect was good. According to the retrospective study of earthquakes in this region, there was also an anomaly peak before the Qinghai Yushu \(M_{\rm L}7.4\) earthquake on 14 April 2010; the anomaly peak occurred in September 2009 and the Xizang Nierong \(M_{\rm L}6.6\) earthquake occurred on 24 March 2010 (about one month prior). The Maduo \(M_{\rm L}7.9\) earthquake was similar to the Yushu earthquake. In the process of the curve turning and falling, the Xizang Biru \(M_{\rm L}6.4\) earthquake first occurred on 19 March, then the Qinghai Maduo \(M_{\rm L}7.9\) earthquake occurred on 22 May (about two months later). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{2}{c}{**Name**} & \multicolumn{2}{c}{**Anomaly-Corresponding Rate (\%)**} & \multicolumn{2}{c}{**Earthquake-Corresponding Rate (\%)**} \\ \hline Time scanning scale (month) & 3 & 6 & 12 & 3 & 6 & 12 \\ \hline \multirow{4}{*}{Study region} & Border regions of Qinghai and Xizang & 50.00 & 66.67 & 75.00 & 71.43 & 100.00 & 100.00 \\  & Western section of southern Tianshan & 50.00 & 66.67 & 100.00 & 71.43 & 85.71 & 100.00 \\ \cline{2-8}  & Central and western sections of the Qilian Mountains & 77.78 & 85.71 & 85.71 & 80.00 & 80.00 & 80.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Anomaly-corresponding rate and earthquake-corresponding rate of different time scanning scales. Figure 3: Border regions of Qinghai and Xizang (within the dashed box) and \(M_{\rm L}\geq 6.3\) earthquakes from January 2021 to December 2021. The spatial scanning calculation of the border regions of Qinghai and Xizang adopted the same seven dominant seismic parameters, which were used in the time scanning. \(M_{\rm L}\geq 3.0\) earthquakes from January 1991 to December 2020 were selected as the training data. The probability spectrum calculation analysis was carried out with a spatial window length of \(2^{\circ}\)\(\times\)\(2^{\circ}\) and a step size of \(0.2^{\circ}\)\(\times\)\(0.2^{\circ}\), with a duration of 1 year and a step size of 1 month. January 2021 was the starting time for extrapolation testing. The Xizang Biru \(M_{\rm L}6.4\) earthquake on 19 March 2021 and the Qinghai Maduo \(M_{\rm L}7.9\) earthquake on 22 May 2021 both occurred in the study area. From the results in Figure 5, it could be seen that there were almost no high-value anomalies in the study area from January to May 2019. In June 2019, sporadic high-value anomalies began to appear near the Xizang Biru region. Afterward, the abnormal area and amplitude gradually expanded and strengthened, reaching their maximum value in December 2020. The Biru \(M_{\rm L}6.4\) earthquake occurred in the abnormal area in March 2021. At the same time, abnormal high points began to appear between Yushu and Maduo in Qinghai from March 2021 (inside the red dashed box in Figure 5). Although the abnormal points were small, they showed a gradually increasing trend. The Maduo \(M_{\rm L}7.9\) earthquake occurred to the northeast of the abnormal points in May 2021. Afterward, the abnormal values in both regions gradually weakened, and the high-value abnormal points near the Maduo earthquake completely disappeared in December 2021. Figure 4: The multi-point sliding extreme-value relevancy (MSER) of the border regions of Qinghai and Xizang. Figure 5: The spatial evolution of the MSER of the border regions of Qinghai and Xizang from January 2019 to September 2021. It was found that there were similar highly abnormal changes in 2010. From January 2008 to 2009, the anomaly gradually increased, and almost reached its maximum value in December 2009. In March 2010, the Xizang Nierong \(M_{\rm L}6.6\) earthquake occurred near the anomaly concentration area. At the same time, the abnormal high-value points also gradually increased near the Yushu region in December 2009 (inside the red dashed box in Figure 6).