研究人員發現台灣的水循環和地震發生的時間有所關聯

 原文網址：https://phys.org/news/2021-04-link-earthquake-taiwan.html

by Bob Yirka, Phys.org

一組台灣、加拿大和美國的研究團隊發現台灣的水循環和當地地震的發生時間有關。在發表於期刊《科學前緣》(Science Advances)的論文中，團隊描述了他們對於台灣水循環的研究，並提出了這和地震的發生時間為什麼有所關連。

地震頻率高的時候通常可以對應地下水位低的時候，反之如此。圖片來源：Ya-Ju Hsu

這項工作始於一位團隊成員注意到台灣的大型地震似乎更常在旱季發生。台灣每年五月到九月會遭受大雨與頻繁的颱風侵襲，在其他月份的雨量則少了許多。之前的研究已經得出由於雨量的劇烈變動，地下水的水位也會跟著劇烈改變。在這項新的成果裡，研究人員猜想這個國家經歷的許多地震之中，是否有一些可以用地下水位下降之後在地底留下的空洞來解釋。為了找出答案，他們蒐集了台灣地震和雨量的資料，其中有些案例可以追溯至數百年前。此外，他們也加入了衛星數據來衡量這個島嶼的儲水量。

研究人員發現地震活動確實在乾季時達到高峰，特別是在兩量最少的二三四月，也就是季風季節即將來臨之前；而地震活動在七月到九月最為平靜，一般來說這也是全年雨量最多的時候。研究人員也發現乾季時地下水的儲量減少通常會讓上方的陸地抬升，使得地震發生的機率提高。最後，他們發現地震牽涉到的因素在台灣東部和西部並不一樣。東部地震的發生模式更加複雜，而且跟天氣之間的關係較少。

研究人員提出台灣地下每年承受的應力也許會讓更深的地方受到的應力提高，有時會導致某些大型地震而撼動這座島嶼。對於世界上一年當中雨量也會經歷劇烈波動的其他地方來說，他們的發現具有相當的啟發。

 

Researchers find link between earthquake timing and water cycle in Taiwan

A team of researchers from Taiwan, Canada and the U.S. has found a link between the water cycle in Taiwan and the timing of earthquakes there. In their paper published in the journal Science Advances, the group describes their study of the water cycle in Taiwan and why it appears to be related to the timing of earthquakes.

The work began when one of the team members noticed that large earthquakes in Taiwan seemed to happen more often in the dry season. Taiwan is subjected to heavy rains and frequent typhoons each year between May and September. In other months, the amount of rainfall is much less. Prior research has shown that because of the dramatic shifts in rainfall amounts, groundwater levels change dramatically, as well. In this new effort, the researchers wondered if reduced groundwater levels, which leave empty cavities below ground, could be behind some of the many earthquakes experienced by the country. To find out, they collected both earthquake and rainfall data for the country, in some cases going back several hundred years. They also added satellite data that allowed for measuring water storage on the island.

The researchers found seismic activity was indeed highest during the dry season, particularly during the driest periods of February, March and April—just before the start of monsoon season. They also found that seismic activity was most quiet from July to September—typically the wettest part of the year. The researchers also found that the decreased water load belowground during the dry season often resulted in the land above rising, which increased the odds of earthquakes occurring. They also found that there were different factors involved in earthquakes that occurred on the east side of the island versus the west. Earthquakes that occurred on the east side of the island had a more complex pattern, and were less related to weather.

The researchers note that the annual stresses to the land beneath the island could be contributing to deeper stresses that occasionally result in ruptures of large faults, leading to some of the larger earthquakes that occasionally rock the island. Their findings could have implications for other parts of the world that experience dramatic fluctuations in rainfall each year.

原始論文：Ya-Ju Hsu, Honn Kao, Roland Bürgmann, Ya-Ting Lee, Hsin-Hua Huang, Yu-Fang Hsu, Yih-Min Wu, Jiancang Zhuang. Synchronized and asynchronous modulation of seismicity by hydrological loading: A case study in Taiwan. Science Advances, 2021; 7 (16): eabf7282 DOI: 10.1126/sciadv.abf7282

引用自：Phys.org. “Researchers find link between earthquake timing and water cycle in Taiwan.”