Earthquakes in Taiwan are linked to seasonal changes in water levels
Earthquakes in Taiwan may be linked to seasonal variations in the water cycle, driven by the Asian monsoon.
Taiwan has both a high frequency of damaging earthquakes and a wide variation in the amount of precipitation and water stored in the ground, as a result of the heavy rains and typhoons that buffet the island between May and September.
Ya-Ju Hsu at Academia Sinica in Taiwan and her colleagues analysed earthquake data in eastern and western Taiwan and found a correlation between seismic activity and fluctuations in the water cycle.
Hsu had initially noticed that many earthquakes of magnitude 6 or greater seemed to occur during Taiwan’s dry season between about February and April.
She and her colleagues analysed seismic data collected between 2002 and 2018, as well as groundwater measurements from 40 monitoring stations and data on how the Earth’s crust changes in response to seasonal water loading.
They found that seismic activity in western Taiwan was highest in the dry season and lowest between July and September, at the end of the monsoon season.
“In the dry season, we see more earthquakes because the water load has been removed,” says Hsu. The researchers found that this decreased groundwater resulted in a peak in the rebounding of Earth’s crust even when under low amounts of stress.
Eastern Taiwan had a more complex pattern of seismic activity. There, deeper earthquakes tended to occur more frequently from December to February.
Shallow earthquakes in this part of Taiwan were also linked to the variations in groundwater level and crust changes, but there was greater variability in their timing.
The researchers also looked at records of 63 earthquakes of magnitude 6 or greater between 1604 and 2018, and found similar trends in the seasonal variation in seismic activity.
The high amount of seismic activity during the dry season may increase the chances of a larger fault system rupturing, resulting in a greater number of major earthquakes, say Hsu.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abf7282
More on these topics: