Loading-induced stress variation on active faults and seismicity modulation in the Kuril Islands-Japan region

Journal article, 2024

The Earth's crust experiences continual stress variations due to the loads of the ocean, atmosphere, and continental water. We investigate if these stress variations can influence the seismicity of the Kuril megathrust, a part of the subduction zone positioned between the Pacific and Okhotsk plates, in the Kuril Islands-Japan region. Using established fault geometries and loading-induced stress variations, we calculate monthly Coulomb stress change resulting from hydrological, atmospheric, and non-tidal ocean loads, as well as their combined effects, from 2005 to 2016. We subsequently compare these stress variations with the observed monthly seismic rate along the Kuril megathrust during the same period. Our analysis reveals a weak but statistically significant positive correlation between the multi-loading-induced Coulomb stress changes and seismic activity, particularly in the shallow segment of the southern Kuril trench near Hokkaido island. This finding suggests that relatively small Coulomb stress changes, on the order of a few kPa, induced by surface loads, have the potential to locally trigger earthquakes within stressed fault systems. We also show that the summed contribution of atmospheric, non-tidal oceanic, and hydrological loads to this seismic triggering differs from the results obtained when taking each load separately. In addition, the relative contribution of each load to the Coulomb stress change varies as a function of time and space. Anticipating future studies, we emphasize the importance of extending the research throughout the entire study period and the interest in considering the cumulative impact of multiple loading sources when investigating their role in seismic activity.