Of all the happenings that could be linked to Climate change or its disciples, the recent Earthquake in Taiwan has been found due to seasonal variations in the water cycle.
Taiwan faces both: frequent disastrous earthquakes as it lies in proximity to Pacific Ring of Fire. It lies witness to a wide fluctuation in precipitation due to heavy rains and typhoons encircling the island between May and September. This consequently changes the water stored in the ground.
Academicians were quick to notice a trend.
Several earthquakes of magnitude 6 or greater apparently occur during Taiwan’s dry season i.e. between about February and April.
Therefore, they collected the data on Earthquakes from Eastern and Western Taiwan between 2002 and 2018.
Alongside, the team gathered Groundwater measurements from 40 monitoring stations and any record on changes in Earth’s crust depending on seasonal water loading.
Findings reveal that in western Taiwan, the seismic activity was highest in the dry season and lowest at the end of the monsoon season, between July and September.
They also looked at more distant record of 63 earthquakes of magnitude 6 or greater between 1604 and 2018. To their awe, similar trends were observed in the seasonal variation in seismic activity of the region.
Higher intensity of seismic activity during the dry season may in turn increase the chances of a larger fault system rupturing wherein the stresses may have built up already, triggering a few more major earthquakes.
Taiwan’s Geographical Imbalance:
Taiwan is located amidst the convergent boundary interaction where the Philippine Sea plate is colliding with the Eurasian plate at a rate of 85 to 90 mm/year.
This region experiences frequent damaging earthquakes, on an average 6+ magnitude earthquake each year and heavy seasonal precipitation of more than 2000 mm/year on average.
This causes annual fluctuations in groundwater levels of 5-15 m, reflecting the Earth’s elastic response to the seasonal water loading.
The study was done by quantifying the spatiotemporal relationship between region’s hydrological cycle and earthquake seasonality and by analyzing time series of seismicity, groundwater level, and the GNSS vertical time series.
“In the dry season, we see more earthquakes because the water load has been removed,” says an expert. This decreases groundwater leading to a peak in the rebounding of Earth’s crust even under low amounts of stress.
Eastern Taiwan has developed a more complex pattern of seismic activity. There, deeper earthquakes tended to occur more frequently from December to February. While the shallow earthquakes in this part were also linked to the variations in groundwater level and Earth’s crustal changes.
However, the peak seismicity rate can occur both in winter as well as summer.
Despite the typhoon-associated rainfall, an increase of shallow events lasting ~2.5 years after typhoon Morakot is related to comparatively low water storage in Taiwan.
But there was a greater variability in timing of these changes in order to be clearly understood.
While the Climate change impacts on Hurricane, cyclones, floods, droughts, is easily recognizable but Earthquakes appeared to be discrete events.
However, we cannot forget that Earth systems are integrated and each sphere: Atmosphere, Hydro, Lithosphere or Biosphere, they are in constant interaction with each other.
The thin layer of gases that hosts the weather and fosters global warming do meet the solid Earth or Geosphere — in such a way as to make climate change an even bigger threat while penetrating Earth.
According to a study in 2009, an earthquake fault that is primed and ready to go is like a coiled spring, may go off with “the pressure of a handshake”.
Indian Himalayas and Earthquakes:
Rainfall has influenced the pattern of earthquake activity in the Himalayas in past, where the 2015 Nepal earthquake took approximately 9,000 lives. Still the threat of future devastating quakes looms over Himalayas.
During the summer monsoons, huge quantities of rain get soaked into the lowlands of the Indo-Gangetic plain, scuffling through the southern mountain ranges and then slowly draining out over the next few months.
This annual rainwater loading and unloading of the crust is mirrored by the level of earthquake activity, which is significantly lower during the summer months than during the winter, even in quiet and young Himalayas.
If the current weather regime can develop earthquakes and magma from the Earth’s crust, it won’t be difficult to imagine how the solid Earth is likely to respond to the large-scale environmental adjustments that accompany rapid climate change.
It is well known now that global average temperatures continue to shoot up at unregulated rates and hence, are more than one degree centigrade higher than during preindustrial times.
The Earth has gained the capability to respond to such changes in ways it wants.