The US Geological Survey lowered its forecast for damage from natural and human-induced earthquakes in 2017, compared with 2016, but parts of Oklahoma and southern Kansas remain at risk of seismicity linked to wastewater injection wells, the agency said Wednesday.
"Millions still face a significant chance of experiencing damaging earthquakes, and this could increase or decrease with industry practices, which are difficult to anticipate," Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project, said in a statement.
The 2017 map shows most of Oklahoma facing more than a 1% chance of earthquake damage, with the north-central part of the state facing a 5%-10% chance and a smaller area within that facing a 10%-12% chance.
USGS said the 2017 forecast decreased from last year because fewer "felt earthquakes" occurred in 2016 than in 2015.
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"This may be due to a decrease in wastewater injection resulting from regulatory actions and/or from a decrease in oil and gas production due to lower prices," USGS said.
About 3.5 million people live and work in the areas of Oklahoma and southern Kansas identified as at risk of induced seismicity.
In 2016, Oklahoma experienced its largest earthquake on record as well as the greatest number of large earthquakes, USGS said.
USGS has connected past Oklahoma earthquakes to injection wells, concluding that the massive volumes of wastewater are changing the underground pressure, lubricating the faults and triggering earthquakes.
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