Frequency magnitude distribution and spatial correlation dimension of earthquakes in north-east Himalaya and adjacent regions

The north-east sector of the Himalaya is one of the most active tectonic belts, with complex geological and tectonic features. The b-value and spatial correlation dimension (D-c) of earthquake distribution in the north-east Himalaya and its adjacent regions (20-32 degrees N and 88-98 degrees E) are estimated in the present study. Based on seismicity and faulting pattern, the region is divided into five active regions, namely the (i) South-Tibet, (ii) Eastern-Syntaxis, (iii) Himalayan-Frontal Arc, (iv) Arakan-Yoma belt and (v) Shillong-Plateau. A homogeneous catalogue of 1,416 earthquakes (mb >= 4.5) has been prepared from a revised catalogue of the ISC (International Seismological Centre). The b-value has been appraised by the maximum likelihood estimation method, while D-c values have been calculated by the correlation integral method; b-values of 1.08 +/- 0.09, 1.13 +/- 0.05, 0.92 +/- 0.05, 1.00 +/- 0.03 and 0.98 +/- 0.08 have been computed for the South-Tibet, Eastern-Syntaxis, Himalayan-Frontal Arc, Arakan-Yoma belt and Shillong-Plateau region, respectively. The D-c values computed for the respective regions are 1.36 +/- 0.02, 1.74 +/- 0.04, 1.57 +/- 0.01, 1.8 +/- 0.01, and 1.83 +/- 0.02. These values are > 1.5, except for the South-Tibet (1.36 +/- 0.02). The b-values around the global average value (1.0) reflect the stress level and seismic activity of the regions, while high D-c values refer to the heterogeneity of the seismogenic sources.