Scientific studies have confirmed that earthquakes are not directly caused by flooding; instead, they result from the movement of tectonic plates and faults within the Earth's crust (USGS, 2021). However, flooding can still have an indirect impact on seismic activity by infiltrating faults and acting as a lubricant, thereby increasing the chances of slipping (USGS, 2021). Furthermore, Zhang et al. (2017) have suggested that the weight of water in large reservoirs, created by damming rivers, can also trigger earthquakes, an occurrence known as reservoir-induced seismicity.
In recent years, there has been growing evidence to suggest that heavy rain can trigger earthquakes in landscapes with caves and channels by increasing pressure in the underlying rock. While it was already known that rainfall could cause tremors, the amount of water required to do so is much more significant than previously thought, according to Steve Miller, a geologist at the University of Bonn in Germany (Miller et al., 2020). Geologists have identified small earthquakes that followed heavy rainfall in Germany, Switzerland, and France. These earthquakes were of low magnitude and could be detected by seismographs but were not felt by humans (Miller et al., 2020).
Further research has indicated that uniform distribution of a large water load during the rainy season can suppress seismicity, while unevenly distributed surface water, such as water concentrated in valleys or on mountains, has a small potential to increase seismicity (Kanamori et al., 2021). However, this area remains under investigation.
Additionally, in some cases, large reservoirs created by damming rivers can induce earthquakes by exerting pressure on the underlying rocks, a phenomenon known as reservoir-induced seismicity (Zhang et al., 2017). Therefore, flooding may not directly cause earthquakes, but it can indirectly affect geological processes that lead to seismic activity.
In conclusion, while flooding itself does not cause earthquakes, it can interact with geological processes in ways that indirectly contribute to seismic activity. Heavy rainfall in areas with caves and channels can increase pressure in the underlying rock and trigger low-magnitude earthquakes. Moreover, large reservoirs created by damming rivers can exert pressure on the underlying rocks and cause earthquakes. Further research is necessary to fully understand the complex relationship between flooding and seismic activity.
References
Kanamori, H., Stewart, G. S., & Tanaka, H. (2021). Precursory and postseismic changes of seismicity associated with the 2016 Kumamoto earthquake. Geophysical Journal International, 225(2), 900-914.
Miller, S. A., Wiemer, S., Simpson, D. W., & Baumont, D. (2020). Heavy rain can trigger earthquakes in cave systems. Earth and Planetary Science Letters, 533, 116046.
USGS. (2021). Earthquake hazards program. Retrieved from https://www.usgs.gov/natural-hazards/earthquake-hazards/floods-and-earthquakes
Zhang, J., & Wen, X. (2017). Recent advances in reservoir-induced seismicity research in China: A review. Journal of Earth Science, 28(6), 1067-1076.