An insight into seismotectonic scenario of the southwestern part of Delhi-NCR and delineation of new faults: Implications to seismic hazard potential

• The study introduces new faults in seismotectonic map of Delhi-NCR. • Role of complex faulting in the southwest Delhi region responsible for the genesis of sparse seismicity in the region. • Evidence for the active rifting of the Alwar sub-basin and how it is influencing thrusting in the other part of the region. • The complexity of the state of stress of the region is also addressed in study. • The role of fluid in the fault network controlling seismogenesis. The southwestern region of the Delhi-National Capital Region (NCR) experiences sporadic micro (M ≤ 3.0) and occasional small (M > 3.0) earthquakes with a seasonal influence. This study integrates remote sensing and seismological data to elucidate the seismotectonic scenario and identify potential unmapped faults. Analysis of DEM data (Cartoset) reveals numerous multidirectional minor faults, some coincident or conjugate to known major faults. Earthquake epicentres spatially correlate with several of these delineated faults. Fault plane solutions suggest a transition from central normal faulting to peripheral thrust faulting. Moment tensor decomposition indicates dominant double-couple mechanisms with significant non-double-couple components for earthquakes ranging from Mw 2.5 to 4.4. A major variation in principal stress orientation is apparent between eastern and western region of the study area. Stress inversion reveals a NW-SE shortening direction and unusual principal axis plunges, suggesting a rare “odd” or “unknown” faulting regime. These findings suggest ongoing rifting in the eastern Alwar basin may be inducing thrusting in the surrounding region along pre-existing Aravalli-Delhi fold belt thrusts. Seismogenesis likely results from a complex interplay of faulting, regional tectonics, and fluid interaction. This study highlights the value of a multidisciplinary approach for unravelling the intricacies of seismotectonic in low-to-moderate seismicity regions, with varying strengths due to diverse structural heterogeneity associated with mapped or unmapped (hidden) faults, which have been delineated in this study, as an additional information for assessing seismic hazard potential for Delhi-NCR.