Characterization and interpretation of seismic signals generated by 7th February 2021, Dhauliganga disaster (India)

Abstract

On 7th February 2021, a rockslide triggered debris flow hit the Rishiganga-Dhauliganga valley in the Chamoli district of Uttarakhand (India). Over 200 casualties and an estimated loss of 202 million USD to the infrastructural establishments were reported due to this disaster. The study area is highly seismically active; therefore, a dense seismic activity monitoring network is available in this region. Recent studies have suggested that geological hazard events have distinct seismic signatures that can be used to identify the event type, detect onset times and duration and interpret the hazard chain evolution. Studying these event-specific seismic signals can be a step forward in designing a landslide detection system for the region. While most previous studies focused on a single event, detailed research on the complete hazard chain is limited. Therefore, in this research, a combination of some signal processing techniques such as band-pass filter, Ensemble Empirical Mode Decomposition (EEMD), Short-time Fourier Transform (STFT), and Power Spectrum Density (PSD) was applied to process and analyze the seismic signal data. The signal data of nine seismic stations located within a 300 km radius of the event location were considered for the study. A detailed signal processing was carried out to obtain a signal with a high Signal-to-Noise Ratio (SNR). The observations were combined with satellite imagery to interpret the event dynamics and understand the complete hazard chain. This study provides a better insight into hazard event characterization and interpretation methodology used for post-hazard assessment and emergency response.