**3. Active tectonic zones**

Several active tectonic zones (TZ) developed in the Indo-Pak Subcontinent (**Figure 1**) during the movement of the Indian plate through the tectonic stages discussed above. These zones are active under compressive stress. The Baluchistan-Karakoram TZ, Himalayan TZ, and Assam-Arakan TZ are present along the northern subduction front of the plate from west to east. A prominent midcontinental TZ, SONATA (Son-Narmada-Tapti) TZ along the NSG (Narmada-Son geofracture), occurs across the plate along a paleo-suture between northern Bundelkhand protocontinent (BPC) and southern Deccan proto-continent (DPC) (**Figure 2**). The tectonic reactivation is taking place due to differential rotating motion between the two proto-cratons along the SONATA TZ. The western pericratonic region covering parts of Maharashtra and entire Gujarat is another active TZ designated here as Gujarat TZ, as evident from the repeated earthquakes in this stable continental region (SCR). The Andaman-Nicobar Island arc is another active TZ as the oceanic plate of northeastern Indian Ocean (Bay of Bengal) is subducting under the arc. These TZs are briefly outlined below.

#### **3.1 Baluchistan-Karakoram TZ**

The Karakoram-Himalayan orogenic belt is the subduction complex along the northwestern periphery of the Indian plate (**Figure 1**). The northernmost projection of the leading edge of the plate in the region of Rawalpindi and Jammu had the first contact with the Eurasian plate. Subsequently, the subduction was affected by northward motion with simultaneous anticlockwise rotation of the plate. Thus, the northwestern part of the leading edge has a transformal relationship with the Afghan craton. The transpressional strike-slip relationship is marked by Chaman transcurrent (CT) and Ornach-Nai transcurrent faults (ONT). The Baluchistan arc marks the subduction complex of the Arabian Sea and the Afghan craton collision [5]. All these faults are presently active making this TZ a prime earthquake-prone zone.
