Earthquakes trigger landslides, with the resulting downpour of mud and rocks blocking riverbeds to form landslide-dammed lakes (LDLs). A global study led by the Earth and Environmental Science Research Team of the Faculty of Science at the Chinese University of Hong Kong (CUHK) found that LDLs are not only the result of earthquakes, but they may also cause earthquakes. This is the very first study to conclude that surface hazards and earthquakes have such a mutual cause-and-effect relationship. Researchers believe that this discovery will help implement precise disaster prevention efforts post-earthquakes.
In 2018, two landslides occurred at Baige on the Qinghai-Tibet Plateau. The volume of the cascades from those two incidents totaled 33 million cubic meters (1.17 billion cubic feet), equivalent to 13,000 Olympic-standard swimming pools, and formed LDLs. The CUHK Earth and Environmental Sciences course members later observed that more than 60 earthquakes occurred in the area within a week after the landslide, a frequency 20 times higher than before the formation of the LDLs.
Increased Water and Pore Pressure Causes Faults to Slip Further Triggering Earthquakes
Assistant Professor Tan Yen-joe of the Earth and Environmental Sciences Program at the Faculty of Science of CUHK, who led the research, said that this study is the first of its kind to confirm that earthquakes can be triggered by natural disasters on the Earth’s crust. He explained that when landslides block river valleys or riverbeds and form LDLs, the rise in water level causes an increase in water pressure, thereby increasing the load on the ground. The lake water will also diffuse into the underground pores and increase the pore pressure. A combination of these two pressure buildups will push the nearby faults to separate and trigger further quakes.Zhang Zhen, the lead author of the study and a postdoctoral researcher in the Earth and Environmental Sciences Program at the Faculty of Science of CUHK, pointed out that the results of this study are of great significance for future earthquake risk management. For example, he cited the 2008 Wenchuan earthquake in China, which triggered more than 100,000 landslides and formed hundreds of LDLs. They may have been one of the factors responsible for some of the subsequent earthquakes that year. This study confirms that natural disasters at ground level and earthquakes could be the cause and effect of each other and may even develop into a recurring vicious cycle.
Melting Glaciers May Also Increase Earthquake Frequency
Liu Min, the second author of the study and a postdoctoral researcher in the Earth and Environmental Sciences Program at the Faculty of Science of CUHK, said that the melting of glaciers would also cause the volume and weight of glacial lakes to increase, forming a structure like an LDL, and may then go through similar processes as the mechanism causing earthquakes. In this respect, global warming may increase the frequency of earthquakes in some high-risk areas.Mr. Tan said that the team will study further in the future whether there were phenomena in other parts of the world exhibiting similar earthquakes caused by the landslide to understand the scale and prevalence of this phenomenon. They will also try to learn more about structures that are similar to LDLs, such as glacial lakes, and their potential links to triggering earthquakes. He added that the huge Baige slope had been moving slowly for decades, and suddenly collapsed in 2018, forcing the evacuation of more than 120,000 people. Therefore, the team hopes to study further the mechanism of the instantaneous collapse of these slow-moving huge slopes to understand whether there are ways to predict sudden landslide disasters.
