Regional Structural Configuration and Seismic Pattern of 'Belt of Schuppen' in Northeast India

Using aerial photographs followed by extensive field checks, a Photo-Geological map for the entire 'Belt of Schuppen' of northeast India has been prepared. The 20 to 30 km wide exposed part of 'Belt of Schuppen' comprises two major thrusts (Haflong-Naga thrust, Disang thrust) and three minor Sub-Thrusts. The Haflong-Naga thrust (frontal thrust of 'Belt of Schuppen') extends NE-SW over a length of 410 km along the break in slope separating the alluvial plain in the west from the ridges of Neogene sedimentary rocks in the east. In the SW at Miyungkhor in the left bank of Jatinga River, it is terminated by Dauki fault. In the NE near Digboi, it is concealed below the alluvium. The Disang thrust (rear thrust of 'Belt of Schuppen') extends NE-SW over a length of 480 km and it defines the eastern margin of Neogene basin. In the SW near Wadrengdisa, it branches out from Haflong-Naga thrust and in the NE at Bulbulia in the right bank of Noa Dihing River, it is terminated by Mishmi thrust, which extends into Myanmar as 'Sagaing fault'. The major thrusts and Sub-Thrusts of belt 'Belt of Schuppen' dtp generally towards SE. Thus the 'Belt of Schuppen' extends between Dauki fault in the SW and Mishmi thrust in the NE over a length of about 500 km. When the SW end of 'Belt of Schuppen' moved upwards and towards east along the Dauki fault, the NE end moved downwards and towards west along the Mishmi thrust, causing it's 'S' shaped bending.

The southern part of 'Belt of Schuppen' extends along the sheared western limb of southerly plunging Kohima synform and it is seismically active. The northern truncated end at Mishmi trust is also seismically active. There is a pronounced seismic gap in the middle part of 'Belt of Schuppen'. The epicenter plots of major earthquakes of Richter magnitude ≥7 in this region reveal that the rupturing at depth which caused these earthquakes are aligned along distinct NE-SW trending parallel zones, perpendicular to the regional compression in NW-SE direction.