Seismic noise environment in and around Dhubri-Chungthang Fault Zone

A network of fourteen broadband seismic stations has been established in the foreland basin of the Bhutan Himalaya to investigate the seismically active Dhubri-Chungthang Fault Zone (DCFZ). To assess station reliability and data integrity, a detailed analysis of ambient noise was carried out. Power spectral density (PSD) estimates were generated for each site, and the recorded noise from January 2024 to December 2024 was compared with globally recognised reference models. The findings indicate that the observed noise levels remain consistently within the global limits. The study also reveals that the instrumental tilt exerts a significant influence on the horizontal channels of broadband sensors. Mapping noise across multiple period bands shows the impact of different noise sources, including human activity, surface and body waves, and atmospheric pressure variations. Temporal fluctuations in noise amplitudes reveal seasonal changes in the short-period, microseism, and long-period bands. Overall, the results characterise the spatial and temporal variability of ambient noise in the area while confirming the stability and robustness of the seismic installations.