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

Abstract

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 the eastern and western regions 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.

Keywords

Delhi-NCR / Seismotectonic / Remote sensing / Fault plane solutions / Moment tensors / Stress inversion / Rifting / Thrusting

CRediT authorship contribution statement

Sudipto Bhattacharjee: Writing – original draft, Visualization, Validation, Software, Methodology, Formal analysis, Data curation, Conceptualization. Sanjay Kumar Prajapati: Visualization, Resources, Methodology. Uma Shankar: Writing – review & editing, Validation, Supervision. O.P. Mishra: Writing – review & editing, Validation, Supervision, Resources, Project administration.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

Sudipto Bhattacharjee highly acknowledges IITM-Desk for fellowship support under the Ministry of Earth Sciences Research Fellowship Programme (MRFP). He extends his gratitude to Dr. R.S. Chatterjee (IIRS Dehradun), Mr. Tamal Samaddar (former MTech student, IIRS Dehradun), and Mr. Ravikant (Research Associate, National Center for Seismology, New Delhi) for sharing remote sensing knowledge and time-to-time advice. The authors thank the National Center for Seismology for providing waveform data and other necessary infrastructural support and computational facilities and supervision of the entire research for completion of this research work.

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