Groundbreaking report documents hundreds of human-triggered earthquakes

A recent report in the Seismological Research Letters journal identifies nearly 730 earthquakes that may have been triggered by human activity.

The Human-Induced Earthquake Database, (HiQuake), is the largest and most complete database of earthquake sequences proposed to have been induced by human activity, according to the HiQuake webpage.

The database resulted from a 2016 Dutch oil and gas company, Nederlandse Aardolie Maatschappij (NAM), meeting. NAM held the meeting to discuss induced earthquakes in the Groningen gas field in the Netherlands, said Miles Wilson, a University of Durham in North East England geophysicist who collected the study's data.

Wilson and his research team were invited to provide a global overview of induced seismicity at the meeting, Wilson said.

Induced seismicity refers to seismic events, typically earthquakes, caused either in part or completely by human activities.

There are a number of human activities that are linked to induced seismicity, according to the HiQuake site.

The most commonly reported human activities proposed to have caused earthquakes are mining and water reservoir impoundment. In recent years, the number of earthquakes proposed to have been induced by fluid‐injection activities has grown.

The most commonly reported maximum magnitude in an induced earthquake sequence is between three and four.

The largest earthquake in HiQuake had a magnitude of 7.9 and occurred in China in 2008. Such large earthquakes release mostly stress of natural tectonic origin but are conceivably triggered by small anthropogenic stress changes.

The HiQuake database will help to improve the overall understanding of induced earthquakes and to manage their impact on society, Wilson said.

“It’s very easy to become focused on a particular earthquake, especially if it directly affects us. HiQuake, although incomplete, provides a bigger global picture than people have ever had access to before,” Wilson said.

There is controversy surrounding cases of induced seismicity and the overall role of human behavior.

“It’s almost impossible to scientifically prove that an earthquake is caused by human activity, which is why many cases are highly debated,” said Wilson.

For example, in the United States, there has been large debate over the role of fracking for natural gas in seismic events.

The U.S. Geological Survey (USGS) addresses some of the myths and misconceptions surrounding fracking and wastewater disposal.

"Fracking is not causing most of the induced earthquakes. Wastewater disposal is the primary cause of the recent increase in earthquakes in the central United States," the USGS website reads.

Fracking is more likely to induce seismic activity indirectly through the disposing of wastewater used in the process. Wastewater disposal is the byproduct of water, sand and chemicals used to hydraulically fracture hydrocarbons from rock. That high-pressure wastewater can crack rocks and lubricate faults.

The HiQuake data shows 29 project sites where earthquakes were induced by fracking itself, 36 sites where quakes were induced by wastewater disposal, and 12 sites where temblors induced by unspecific oil, gas, and wastewater disposal.

The potential risks of fracking have led to political and social debate.

“Whether or not a nation allows fracking is up to the governing body, but that decision needs to be based on scientific research and not on public perception,” Wilson said.

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Many proposed cases of induced seismicity are controversial. When figuring out which cases to contain on the database, HiQuake decided to include all induced cases proposed on scientific grounds to the database, Wilson said.

“Filtering HiQuake using our judgment would not be a rigorous scientific method,” Wilson explained. “Any judgment calls we leave to users.”

HiQuake includes data drawn from publications that span almost a century. The authors estimate under-reporting to be about 30 percent for magnitude 4 events, about 60 percent for magnitude 3 events, and about 90 percent for magnitude 2 events.

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While it is rare for human-induced earthquakes to cause disruptions, some cases may be a significant problem, such as the hydrocarbon-producing areas of Oklahoma, according to the HiQuake abstract.

The potential disruptions of induced earthquakes is increasing as the size of projects and density of populations increase. Therefore, effective management strategies are needed, according to the HiQuake abstract.

“To completely eliminate induced earthquakes, you would have to stop any human activity which influences the forces acting in the Earth’s crust,” Wilson said.

This is not practical in a world where resource demands are ever growing in response to population growth and development, Wilson said.

“However, the risk of induced earthquakes can be reduced by continued research into their causes and by assessing project sites as best as possible before operations commence,” Wilson said.

Wilson and his research team plan to continue to keep HiQuake updated with new scientific research as it continues to evolve. NAM has recently agreed to continue funding the project for another two and half years, according to Wilson.

“We plan to keep HiQuake as an up-to-date resource which is accessible to anyone, anywhere and at any time,” Wilson said.

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