Distribution of b‐values in Indo‐Burma Ranges, northeast India: Implications to structural heterogeneities and style of faulting.

The spatial distribution of the b‐value has been determined using a homogeneous earthquake catalogue from 1964 to 2018 to examine the characteristics of structural heterogeneities and their bearing on the style of faulting in the Indo‐Burma region of Northeastern India. The study region is associated with an uneven distribution of structural heterogeneities and demonstrates the mixed type of faulting, nature where the majority of earthquakes resulted mainly by thrust and strike‐slip fault. Our critical analysis demonstrates that the existence of two prominent zones is associated with high b‐values and low b‐values where the mixed type of faulting resulted in the genesis of seismicity in the study area. The high b‐values in the study area contain a large number of smaller earthquakes whilst the low b‐values comprise a smaller number of larger earthquakes distributed along with the Naga‐Disang Thrust, Kabaw Fault, and Sagaing fault systems. A close comparison between b‐values and different faulting styles reveals that the area containing a low b‐value suggests stronger seismogenic zones, where an accumulation of strain energy leads to the genesis of seismicity by thrust faulting with slight slip component whilst Indo‐Burma Ranges regions connected with b‐values (0.5–0.9) demonstrate strike‐slip to the normal mode of faulting, indicating relatively weak seismogenic zones where tensional forces are prevalent. The depth sections illustrate that lower b‐values for the upper part of the subducting slab correspond to more stress generated by tectonics compared to that of the lower part, and interestingly the deeper part of the subducting Indian slab is coupled with conspicuously very high‐b values, suggesting the weakening of the Indian subducting slab through dehydration. [ABSTRACT FROM AUTHOR]