The sedimentary rocks found in the northern of the main boundary fault and in inner part of the lesser Himalaya are predominantly weak slate to massive and thick beaded dolomite.

Also the imbricate faults, tight folds thrust, cleavage and various systems of joint are encountered in the main boundary fault zone.

a. Folds: A fold is a non-planer configuration of rocks resulting from deformation. When rock layers are subjected to the stress, they fold. Fold forming rocks, being highly stressed, are not considered stable.

b. Faults: Faults are ruptures along with the opposite walls, which have moved passing each other. In rivers fault, footwall (the underlying side of a fault) moves down relation to the hanging wall (the overlying side of a fault). So, shortening of rock-layer occurs. It is extending and shortening stage of rock and forms unstable condition. Hence, faulted areas are hazardous in nature. Also, the faulted terrain is generally very friable and crushed. Hydrothermal fluids may come out through them resulting in weakening of the rocks. Such rocks are more susceptible to attack by rain, river and frost action. So, the faulted terrain is highly unstable.

c. Joints: A surface of fracture without displacement is called joint. A group of more or less parallel joints is known as joint set. When two or more joint sets intersect, they form a joint system. As joint result from tension on rock mass jointed terrain can be considered as an unstable region.

d. Thrust: Low angle reverse faults are called thrusts. Due to thrust, great shortening of the layers takes place. As a result, softer rocks undergo toppling. Due to activeness of the Himalayan frontal thrust and the main boundary thrust in Himalayan range, the entire area is seismically hazardous.

e. Cleavage: Cleavage consists of parallel to sub-parallel fractures often oriented normal to the principal stress. They create less stability since they are small-scale structures.