A Uniformly Processed Strong-Motion Flat-File for Crustal Earthquakes across the Indian Region

Strong-motion flat-files form the backbone of ground-motion modelling and seismic hazard assessment, yet India has long lacked a uniformly processed, comprehensive strong-motion database aligned with international standards. The study addresses this critical gap by developing a systematically processed ground-motion flat-file for earthquakes recorded across the Indian subcontinent, particularly for the Himalayan region where seismic hazard remains high and strong-motion data are sparse. The compiled flat-file includes 778 manually processed accelerograms from 195 earthquakes spanning the time period 1986-2018. These events, with moment magnitudes M_w ≥ 2.0 and epicentral distances R_epi < 600 km, were recorded at 254 seismic stations. The diversity of source-to-site configurations captured in this dataset enhances its applicability for developing regionally representative GMMs and for examining spatial variations in ground-motion characteristics. The waveform processing followed a consistent step-by-step protocol involving baseline correction, tapering, filtering, windowing and signal-to-noise ratio. The resulting flat-file contains a comprehensive suite of Intensity Measures (IMs) including Peak Ground measures (PGA, PGV, PGD), Spectral Acceleration (SA), Fourier Amplitude Spectrum (FAS), Effective Amplitude Spectrum (EAS), Arias intensity (AI), Cumulative absolute velocity (CAV), Significant Duration (SD), Acceleration Spectrum Intensity (ASI), Velocity Spectrum Intensity (VSI), and Characteristic Intensity (Ic). The reliability of the processed IMs was validated through residual analysis of FAS against an empirical model. As the first uniformly processed strong-motion flat-file for India that includes both horizontal and vertical components, this dataset provides a much-needed foundation for advancing ground-motion modelling and seismic hazard assessment in the region. Overall, this flat-file significantly strengthens the database, evaluates attenuation behaviour, conducting parametric and near-field ground-motion studies, and supporting site-specific seismic hazard assessments across the Indian region.