Practical Guidelines for Determining Usable Bandwidth for SSA2 Accelerograms of Iran Strong Motion Network (ISMN)

Samaei, Meghdad; Karashi, Jafar

doi:10.48303/jsee.2026.2066111.1153

Practical Guidelines for Determining Usable Bandwidth for SSA2 Accelerograms of Iran Strong Motion Network (ISMN)

Articles in Press

Document Type : Research Article

Authors

Meghdad Samaei ¹

Jafar Karashi ²

¹ Mahallat Institute of Higher Education

² Université Grenoble Alpes

10.48303/jsee.2026.2066111.1153

Abstract

Seismic data processing in engineering seismology often involves band-pass filtering, a critical step in analyzing strong-motion records. We present a systematic methodology to determine the usable frequency band—defined by a low-cut frequency (flc) and a high-cut frequency (fhc)—for each of 501 single-component SSA2 accelerograms (derived from 167 three-component records) from Iran Strong Motion Network (ISMN). Our workflow combines zero-order baseline correction, S-wave Fourier Amplitude Spectrum (FAS) analysis, noise-floor estimation, SNR-based thresholds (normalized for window length), spectral-shape evaluation (ω² model), and iterative visual inspection of filtered time series. Applying this procedure to the 501 traces, we find median limits of flc = 0.12 Hz and fhc = 14.8 Hz. Approximately 90% of the records maintain a usable bandwidth entirely within the 0.35–8 Hz range, and all records span at least one decade in frequency. These results provide a transparent and reproducible basis for selecting filter bands in strong-motion studies.

Keywords

Strong ground motion

usable bandwidth

band pass filtering

SSA2 accelerograms

Iran Strong Motion Network

Subjects