Earth science
A SWARM of thousands of earthquakes in Japan, lasting for years, was probably triggered by environmental factors like rain, heavy snow and rising sea level. “The changing climate can have some impact on the stress state of the Earth beneath our feet,” says Qing-Yu Wang at the Massachusetts Institute of Technology.
The shaking began in Japan’s Noto peninsula on the island of Honshu near the end of 2020. Since then, the area has experienced more than 100 small earthquakes per day. On the first day of 2024, the region felt a large magnitude-7.5 earthquake that destroyed tens of thousands of buildings and killed at least 240 people. But it is unclear whether that quake fits within the swarm.
Wang and her colleagues analysed seismic activity in the region between 2012 and 2023 to investigate what triggered the swarm, which ranks among the largest ever observed. These swarms commonly erupt in volcanic regions, but typically last weeks or months.
The researchers suspected that these partly stem from a rise in the pressure of fluid within porous rocks located kilometres underground.
100+ This many earthquakes have been hitting part of Japan a day
With such excess pressure, “the whole structure becomes weak”, says Wang.
Fluctuating weight on the surface from sources like rain, snow, atmospheric pressure and sea level can also shift pore pressure, she says. When combined with high pressure from fluid below, it could trigger earthquake swarms.
So, the team modelled the influence of upwelling fluids and variations in surface weight on pore pressure. Snowfall seemed to have the greatest influence of all surface factors. When the researchers included snow’s influence in their model, the correlation with seismic measurements improved by 10 per cent compared with a model without snow. A clear seasonal pa
