What's Causing So Many Earthquakes in Oklahoma?

[Judi Lynn]

By Sarah B. Puschmann, Staff Writer | August 3, 2017 03:30pm ET


A magnitude-4.2 earthquake hit just outside Edmond, Oklahoma, last night (Aug. 2) at 9:56 p.m. local time — the fifth significant temblor to shake this region of the state already this month, according to the U.S. Geological Survey.

The temblor originated at a depth of 1.9 miles (3 km), about 15 miles (24 km) northeast of Oklahoma City, the USGS said. According to the Edmond police department's Twitter account, as of last night, no significant damage had been reported. News 9 in Oklahoma City reported that although 4,600 people were left without power after the quake, all power has since been restored. [The 10 Biggest Earthquakes in History]

But last night's quake is part of a recent trend. Since Tuesday (Aug. 1), five earthquakes above magnitude 3.0 have been reported in this region, Xiaowei Chen, assistant professor of geophysics at the University of Oklahoma, told Live Science. It appears to be part of a longer sequence of earthquakes that began in 2014, she added. In fact, in 2014, the USGS issued an earthquake warning in the central part of the state — the first time the agency had ever issued such a warning for a state east of the Rockies.

Chen didn't yet know enough about the most recent earthquake sequence to be able to comment on whether this recent magnitude-4.2 earthquake may signal that an even bigger earthquake will come, or if it's simply within the range of expected seismic activity in the area, she said.

More:
https://www.livescience.com/60032-earthquakes-shake-oklahoma.html?utm_source=notification

[blondebanshee]

1. One word: FRACKING

[elleng]

2. THIS?

[lunasun]

3. Duh

[sinkingfeeling]

4. No doubt, fracking.

[OKIsItJustMe]

5. The USGS has a helpful site

https://earthquake.usgs.gov/research/induced/

One of the pages on the site has to do with “fracking” and induced earthquakes (please note, material from USGS. Copyright concerns are nil.)

https://earthquake.usgs.gov/research/induced/myths.php

Induced Earthquakes

Myths and Misconceptions

What you do and don’t know about induced seismicity

Fact 1: 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.

Wastewater disposal wells typically operate for longer durations and inject much more fluid than hydraulic fracturing, making them more likely to induce earthquakes. Enhanced oil recovery injects fluid into rock layers where oil and gas have already been extracted, while wastewater injection often occurs in never-before-touched rocks. Therefore, wastewater injection can raise pressure levels more than enhanced oil recovery, and thus increases the likelihood of induced earthquakes.

Fact 2: Not all wastewater injection wells induce earthquakes.

Most injection wells are not associated with felt earthquakes. A combination of many factors is necessary for injection to induce felt earthquakes. These include: the injection rate and total volume injected; the presence of faults that are large enough to produce felt earthquakes; stresses that are large enough to produce earthquakes; and the presence of pathways for the fluid pressure to travel from the injection point to faults.

Fact 3: Wastewater is produced at all oil wells, not just hydraulic fracturing sites.

Most wastewater currently disposed of across the nation is generated and produced in the process of oil and gas extraction. As discussed above, saltwater is produced as a byproduct during the extraction process. This wastewater is found at nearly every oil and gas extraction well.

The other main constituent of wastewater is leftover hydraulic fracturing fluid. Once hydraulic fracturing is completed, drilling engineers extract the fluids that are remaining in the well. Some of this recovered hydraulic fracturing fluid is used in subsequent fracking operations, while some of it is disposed of in deep wells.

Fact 4: The content of the wastewater injected in disposal wells is highly variable.

In many locations, wastewater has little or nothing to do with hydraulic fracturing. In Oklahoma, less than 10% of the water injected into wastewater disposal wells is used hydraulic fracturing fluid. Most of the wastewater in Oklahoma is saltwater that comes up along with oil during the extraction process.

In contrast, the fluid disposed of near earthquake sequences that occurred in Youngstown, Ohio, and Guy, Arkansas, consisted largely of spent hydraulic fracturing fluid.

Fact 5: Induced seismicity can occur at significant distances from injection wells and at different depths.

Seismicity can be induced at distances of 10 miles or more away from the injection point and at significantly greater depths than the injection point.

Fact 6: Wells not requiring surface pressure to inject wastewater can still induce earthquakes.

Wells where you can pour fluid down the well without added pressure at the wellhead still increase the fluid pressure within the formation and thus can induce earthquakes.

…