When seismologists look for an earthquake's cause, they normally search underground. Centuries of studies have made it clear that the collision of tectonic plates and the movement of faults are the major factors that trigger a tremor. However, a new study suggests that certain weather events can also generate earthquakes.
Unusual Swarm of Earthquakes
Since late 2020, the Noto Peninsula in Japan has been shaken by hundreds of small earthquakes. The seismic events are unlike the ordinary earthquake sequence, which begins with a main shock leading to a series of aftershocks before vanishing. Instead, the tectonic activity in the region is an earthquake swarm or a pattern of several ongoing tremors with no obvious main trigger.
The swarm of crustal earthquakes in the northeastern region of the Noto Peninsula is far from the plate boundaries of the subducting Philippine and Pacific plates. It is also responsible for hundreds of tremors experienced every day.
The inland crustal earthquakes in Japan islands also occur at relatively shallow depths, unlike typical subduction zone interplate earthquakes. Analysis shows that the swarm of earthquakes in Noto began at a depth of about 9.32 miles (15 kilometers) and has since traveled northeast toward the surface. This distinct pattern suggests that rather than inter-earthquake stress interactions, an underlying force drives the earthquakes in the swarm to failure.
Precipitation and Ground Shaking
In the paper "Untangling the environmental and tectonic drivers of the Noto earthquake swarm in Japan," scientists report that heavy rain and snowfall episodes likely contributed to a swarm of earthquakes in northern Japan over the past several years. This investigation is the first to show that weather conditions can actually initiate some tectonic activities.
Led by Qing-Yu Wang from the Massachusetts Institute of Technology, the research team focuses on a series of ongoing earthquakes in the Noto Peninsula in Japan. In collaboration with Japanese scientists, they aimed to detect any patterns in the earthquake swarm that explain the region's persistent shakings.
The team started by looking through the catalog of earthquakes from the Japanese Meteorological Agency, which provides data on seismic activity throughout Japan over time. Using the seismic data from the catalog, they counted the number of seismic events that took place in the Noto Peninsula over the last 11 years.
They found that seismic activity in the area is synchronized with changes in underground pressure, and those changes are affected by seasonal patterns of rain and snowfall. The team suspects that this newly discovered connection between earthquakes and climate may not be exclusive to Japan and may also explain the shaking in other parts of the planet.
In the future, experts predict that the influence of climate on earthquakes can be more pronounced with global warming. According to study author William Frank, as climate change causes more extreme precipitation events, they expect a redistribution of water in the continents, oceans, and the atmosphere, changing how the crust of the Earth is loaded.
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