## 3 Earthquake Early Warning System for Bursa Province (Turkiye) and Its Surroundings
### Determination of Magnitude Equation Coefficients for Bursa Province (Turkiye) and Its Surroundings  
EPIC was developed and optimized for California. [PERSON] et al. [36] and [PERSON] and [PERSON] [11] found it beneficial to adjust the magnitude relation equations of EPIC in order to optimize EPIC for different regions, such as Korea and Israel, respectively. EEW applications frequently use relationships derived from the first few seconds of the P wave for earthquake magnitude estimation [37; 38; 39; 40; 31]. In this study, we evaluate \(Pd\) and \(T_{p}^{max}\) to estimate magnitude. For the magnitude- Pd scaling relationship, a linear regression model assumption was made between logarithmic \(Pd\), observed magnitudes (\(M\)), and epicentral distance (\(R\)) [39]. The linear relationship between magnitude and \(T_{p}^{max}\) is shown by the least squares fit between the \(M\) and mean \(T_{p}^{max}\) values from each station for each event [41; 42]. Kandilli Observatory and Earthquake Research Institute-Regional Earthquake and Tsunami Monitoring Center [43] earthquake catalog consists of 275 earthquakes with a magnitude \(3.5<M<7.0\) between 1 January 2012, and 30 November 2021. A total of 275 earthquake data were examined and 104 earthquakes with data quality suitable for replaying in EPIC (Table 1) were studied. The seismic recordings used for regression analysis consist of strong motion and broadband waveforms. Following previous studies [42; 44; 39], we applied a 0.075 Hz high-pass Butterworth filter to the data. We used KOERI locations to calculate epicentral distances and P-wave onsets for each station and Matlab software (R2021b) to calculate \(Pd\) and \(T_{p}^{max}\) values from the first 4 s of the seismograms. Vertical component velocity seismograms were used in the analyses. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**Date**} & **Origin Time** & **Latitude** & **Longitude** & **Depth (km)** & **Magnitude** \\ \cline{1-1}  & & & **(UTC)** & **Latitude** & **Longitude** & **Depth (km)** & **Magnitude** \\ \hline
1 & 27 November 2013 & 04:13:37.5 & 40.846 & 27.919 & 10.8 & 4.7 \\  
\hline \hline \end{tabular}
\end{table} 
Table 1: List of earthquakes (\(M\geq 3.5\)) recorded by KOERI that occurred in Bursa province and its surrounding area between 1 January 2012 and 30 November 2021. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**No** & **Date** & \begin{tabular}{c} **Origin Time** \\ **(UTC)** \\ \end{tabular}  & **Latitude** & **Longitude** & **Depth (km)** & **Magnitude** \\ \hline
29 & 7 February 2017 & 02:24:02.9 & 39.524 & 26.124 & 12.7 & 5.3 \\
30 & 8 February 2017 & 01:38:03.2 & 39.531 & 2  
As a result, the best-fitting attenuation relationship for the resulting \(log(Pd)\) is given as:  
\[log_{10}(Pd)=-4.78+0.9M-1.34\ log_{10}(R) \tag{3}\]  
with a coefficient of determination of 0.639. Figure 3 contains a comparison of the observed \(Pd\) values with the values estimated by Equation (3) for the magnitudes 3.0, 4.0, 5.0, 6.0, and 7.0, respectively, separately. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**No** & **Date** & **Origin Time** & **Latitude** & **Longitude** & **Depth (km)** & **Magnitude** \\ \hline  
arch 2021 & 21:33:56.5 & 40.516 & 28.153 & 7.7 & 3.6 \\
104 & 19 June 2021 & 12:07:52.7 & 40.950 & 29.213 & 14.6 & 4.0 \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 3: The relationships between \(Pd\), epicentral distance (\(R\)), and catalog magnitude (\(M\)) calculated for each station. Each triangle is measured at a single site. Here, Pd is in cm, and R is in km. Thick lines are predictions based on Equation (4) for magnitudes 3 (red line), 4 (blue line), 5 (green line), 6 (black line), and 7 (yellow line), and thin lines are for magnitudes 2.5, 3.5, 4.5, 5.5, and 6.5, respectively.