# Advanced Unified Earthquake Catalog for North East India
## 8 Discussion and Conclusions  
A homogenous earthquake catalog is of critical importance to understanding the seismicity of a seismic region. A total of 9969 events during the period 1737-2012 for NE India have been considered in this study. As the M\({}_{\rm w}\) scale was mainly derived and validated for the Southern California region, therefore, a globally valid seismic moment magnitude scale M\({}_{\rm wg}\) is reported in recent literature. Improved GOR (GOR1) relationships for converting m\({}_{\rm b}\) and M\({}_{\rm S}\) to M\({}_{\rm wg,GCMT}\) has been developed for the study region. For converting surface wave magnitudes to M\({}_{\rm wg}\) magnitudes, conversion relations have been developed for the ranges. 4.1 \(\leq\) M\({}_{\rm s,ISC}\)\(\leq\) 6.1 and 4.2 \(\leq\) M\({}_{\rm s,NEICE}\)\(\leq\) 6.1, based on data 93 and 57 events, respectively. Similarly, Body wave magnitudes (m\({}_{\rm b}\)) are converted into M\({}_{\rm wg}\) scales following \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Seismogenic Zone** & **M\({}_{\rm c}\)** & **’b’** & **’a’** \\ \hline I & 3.4 & 0.6 & 5.02 \\ \hline II & 3.5 & 0.66 & 5.51 \\ \hline III & 3.9 & 0.7 & 4.96 \\ \hline IV & 4.1 & 1.09 & 6.52 \\ \hline V & 3.1 & 0.5 & 3.98 \\ \hline VI & 3 & 0.45 & 3.84 \\ \hline VII & 3.1 & 0.69 & 4.87 \\ \hline VIII & 3.2 & 0.61 & 3.85 \\ \hline IX & 3.3 & 0.65 & 4.92 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Estimated 'M\({}_{\rm c}\)’, 'b,’ and ‘a’ values for various seismogenic zones. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **M\({}_{\rm wg}\)** & **M\({}_{\rm w}\)** \\ \hline M\({}_{\rm c}\) (1964–1990) & 4.1 \(\pm\) 0.17 & 4.7 \(\pm\) 0.13 \\ \hline b & 0.98 & 1.27 \\ \hline a & 7.56 & 8.98 \\ \hline M\({}_{\rm c}\) (1964–2000) & 4 \(\pm\) 0.17 & 4.4 \(\pm\) 0.17 \\ \hline b & 0.85 & 0.95 \\ \hline a & 6.86 & 7.57 \\ \hline M\({}_{\rm c}\) (1964–2012) & 3.4 \(\pm\) 0.11 & 4.1 \(\pm\) 0.13 \\ \hline b & 0.61 & 0.8 \\ \hline a & 5.73 & 6.96 \\ \hline No. of Clusters & 942 (22.381\%) & 1232 (31.882\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Difference in seismicity parameters between M\({}_{\rm wg}\) catalog and M\({}_{\rm w}\) catalog for different time periods. the GOR1 methodology. The \(\rm m_{b,ISC}\) to \(\rm M_{wg,GCMT}\) conversion relationship has been developed using 116 event data for magnitude range \(4.8\leq m_{b,ISC}\leq 6.1\), while the \(\rm m_{b,NEIC}\) to \(\rm M_{wg,GCMT}\) conversion relationship is derived for magnitude range \(4.8\leq m_{b,NEIC}\leq 6.1\) based on 106 events. A significant difference between \(\rm M_{w}\) and \(\rm M_{wg}\) estimations has been observed from various observed magnitudes such as \(\rm m_{b}\), \(\rm M_{S}\), \(\rm M_{L}\) and \(\rm M_{D}\). Therefore, these differences in the seismic moment magnitude scales will lead to serious biased in the seismicity parameters and, consequently, in seismic hazard results (Table 5, [31]). Only MMI intensity 5 and above data were utilized to construct an empirical relationship between intensity (\(\rm I_{max}\)) and Seismic moment magnitude \(\rm M_{wg,GCMT}\). In total, 29 MMI intensities and \(\rm M_{wg,GCMT}\) data pairs are included from the entirety of India. The MMI empirical relationship for intensities 5 and higher is mostly compatible with the Indian seismic zoning chart, which shows the range of values associated with the major seismic zones according to the seismic code (IS, 2002) released by the Bureau of Indian Standards (BIS) [38]. Developed intensity-seismic moment magnitude relationship should be used to convert historical earthquakes to DMS (Das Magnitude Scale) scale when magnitude information is unavailable. The declustering of the homogenized catalog for the time being 1737-2012 is carried out using the Ref. [36] procedure, and there is a reduction of 2231 events (22.38%) during this process. The entire homogenized earthquake catalog has been classified into four catalog periods, namely 1737-1963, 1964-1990, 1964-2000, and 1964-2012.