Active segmentation assessment of the tectonically active South Wagad Fault in Kachchh, Western Peninsular India

- An active fault have been mapped east of 2001 Mw 7.7 Bhuj earthquake.
- The fault zone morphology of SWF shows an anastomozing fault pattern.
- The compressional strain of 0.05 μstrain/y inferred from GPS study in the SWF area attests the activeness.
- The landform development along a river valley in the SWF zone suggests reactivation of the SWF between 12 to 3 ka.
- The southern front of Wagad is found to be uplifting 2.8 mm/y during the last 12 ka as estimated through OSL dates.

ABSTRACTIn present study the results of integrated studies of landform development and geomorphic indices of drainage networks across the South Wagad Fault (SWF) zone have been presented. The SWF is a structure that is morphogenic in nature, creating a 40-m-high E-W trending escarpment that extends ~ 80 km at the southern end of the Wagad uplift. The SWF got reactivated during the Bhuj earthquake of 2001, continued aftershock activity of M ≥ 4 levels were recorded in the epicentral zone, north of the Kachchh Mainland Fault and west of the SWF. Strath terraces along the river valleys and the truncation of alluvial fans along the mountain front, incision, and offset of rivers suggests an active nature of the SWF. To assess the relative tectonic activity, morphometric indices such as stream-gradient (SL) index, hypsometric integral (HI), basin asymmetry (AF), mountain front sinuosity (Smf) index, sinuosity index (SI), and basin shape (BS) have been analyzed. The landform development along the river valley in the SWF zone suggests reactivation of the SWF between 12 and 3 ka. The southern front of Wagad is found to be uplifting at the rate of 2.8 mm/y during the last 12 ka as estimated through OSL dates. The relative index of active tectonics (RIAT) by the study of different geomorphic parameters and field checks indicates that most of the Wagad highland is active. The compressional strain of 0.05 μstrain/y inferred from the GPS study in the SWF area attests to the activeness.