Commentary: Is Sichuan more prone to earthquakes?

Commentary: Is Sichuan more prone to earthquakes?

China’s Sichuan earthquake this week suggests urgent scientific research and analysis are needed to understand whether human activities have increased seismic activity, says Earth Observatory’s Assistant Professor Wei Shengji.

EOS singapore Sichuan earthquake
The image above shows the recent magnitude-5.8 earthquake sequence in Yibin, Sichuan, China, against a background seismicity of the past 10 years (2009 – 2019). (Photo: Earth Observatory Singapore)

SINGAPORE: Barely 10 years since the Great Wenchuan earthquake in Sichuan, China, the province has been rocked by another high-profile earthquake.

And amid social media chatter over its causes, a key question that has arisen is this: Did fracking have anything to do with Monday’s earthquake? Here’s what we know so far.

The magnitude-6.0 earthquake that struck the southern edge of the Sichuan basin near Yibin county on Monday has so far resulted in at least 12 deaths and 134 hurt, and reports of the ground shaking came from regions located as far as a few hundred kilometres from the earthquake’s origin.

Rescuers search for earthquake survivors in the rubble of a building in China (1)
Rescuers search for earthquake survivors in the rubble of a building in Yibin, in China's southwest Sichuan province early on Jun 18, 2019. (Photo: AFP)

SICHUAN A SEISMICALLY ACTIVE AREA

Historically, we know that the Sichuan basin is often rocked by earthquakes. This is because it is surrounded by plate tectonic blocks that are seismically active.

The Basin’s northwestern edge is in continual collision with the Tibetan Plateau, which is moving in a southeast direction, causing the entire region to be frequently stricken by earthquakes.

Back in 2008, the build-up of strains between the blocks resulted in the devastating magnitude-7.9 earthquake in Wenchuan.

This recent Yibin earthquake originated somewhere between the Sichuan basin and the Yunnan-Kweichow plateau. Like the basin, this plateau is also a seismically-active block that currently experiences strong deformation and orogenic processes.

So is the seismicity of the Sichuan region the sole cause of this earthquake? There are other factors.

COULD FRACKING LEAD TO EARTHQUAKES?

Hydraulic fracking activity has been on the uptick not only in China, but all over the world in the last decade, as countries race to increase oil and gas production. The discovery of shale reserves has been a boon for many countries.

A new study has linked fracking to a November 2017 earthquake in South Korea that injured scores of
Study has linked fracking to a November 2017 earthquake in South Korea that injured scores of people (Photo: AFP/DAVID MCNEW)

A study published in the US journal Seismological Research Letters by geologists Lei Xinglin, Wang Zhiwei and Jinrong Su argued that fracking operations have been responsible for smaller quakes in the Sichuan basin.

They have shown there is a correlation between increases in seismic activity and areas of oil and shale gas exploration.

READ: China rejects claims fracking caused Sichuan quake: State media

But, even though the Sichuan region is susceptible to induced earthquakes that are triggered by fracking, it has always been vulnerable to such hazards because of its geology.

We need more scientific research and analysis to better understand the relationship between this most recent earthquake and human activities, and establish if it is a cause-and-effect one. 

BETTER MONITORING

The good news is, since the Wenchuan earthquake in 2008, overall seismic monitoring and earthquake studies have greatly improved in China, especially in the Sichuan region.

Denser broadband and strong-motion seismometers have been deployed. Data is transferred in real time to both local and international data centres.

This stream of real-time data is critical in earthquake early-warning systems. The idea of early warnings for earthquakes is to take advantage of the faster propagating but smaller primary waves to quickly determine the location, timing, and magnitude of the quake in as short a time as possible after its occurrence.

READ: How data-sharing by Big Tech can save lives in disasters, solve new problems, a commentary

Based on this information, we can then warn people located in regions further away of any impending destructive secondary waves that may be stronger and more destructive.


SICHUAN RECEIVED EARLY WARNING

Such a system has been tested in many regions in the Sichuan province including this week. It was reported that people hundreds of kilometres away, in Chengdu for example, received the warning message after the Yibin earthquake had occurred.

The major challenge in such warning systems is how fast and accurate the warning message can be issued. If it takes too long, the warning then becomes less meaningful.

Rapid and accurate early warning for earthquakes is still a cutting-edge research topic for both scientists and engineers that requires detailed work to determine the causes of such seismic activity and save more lives. 

Assistant Professor Wei Shengji is Principal Investigator at the Earth Observatory of Singapore.

Source: CNA/nr(sl)

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