Linking climate change, hydrological loading, and seismic activity in the Himalayas

The Himalayas exhibit ongoing convergence and geodetic deformation driven primarily by tectonic forces. However, climate change and its associated secondary factors, including terrestrial water storage and atmospheric and non-tidal ocean loading, are some non-tectonic forces that may be influencing the seismicity of the region. The temperature increase has resulted in glaciers melting, and the release of the mean glacial ice load may cause post-glacial rebound. Changing precipitation patterns and groundwater exploitation can produce stress and pore-fluid pressure near critically stressed faults and fractures, triggering regional seismic activity. This study investigates the relationship between climatic parameters and seismicity in the Himalayas, characterised by a thrust fault mechanism. Also, we examine the long-term hydrological loading effect from Gravity Recovery and Climate Experiment (GRACE)-derived datasets in the Himalayas. The results indicate that the impact of temperature and precipitation anomalies on the occurrence of earthquakes (Mw: 2.0–6.0) is statistically insignificant based on the available datasets. In terms of terrestrial water storage, our analysis indicates that the frequency of minor earthquakes (Mw: 3.0–4.0) increases for the Eastern Himalayas with the decline of terrestrial water storage (TWS), which is statistically significant; however, the result is inconsistent for other magnitude bins and seismic zones indicating insufficient statistical evidence to support a long-term increase or decrease in seismicity rates as a consequence of TWS variation.