November 6, 2011 – Another, Much Larger, Earthquake Struck Central Oklahoma: A 5.6 magnitude quake rocked Oklahoma late Saturday, leaving cracked buildings and a buckled highway. The 5.6 magnitude tremor was 22 times stronger than the earlier 4.7 quake (see last paragraph for an explanation). Unspecified damage to buildings located close to the quake’s epicenter was reported by the Lincoln County Emergency Management department. “Very significant damages are being reported in southern Lincoln County,” the department stated. An emergency manager in Lincoln County later said U.S. 62, a highway in the region, had crumbled in places. The reports in the late-night hours were sketchy and the extent of damages remained uncertain early Sunday. The quake was one of several to rattle the state Saturday. A 4.7 magnitude quake struck roughly 21 hours earlier the same day. There were 12 aftershocks, measuring between 2.7M and 4.0M, between the 4.7M and the 5.6M. The quake was the most powerful on state record. The quake struck at 10:53 p.m. local time Saturday and was centered about 44 miles ENE of Oklahoma City.
The quake struck near the community of Sparks — in eastern Oklahoma between Oklahoma City and Tulsa (see map). The temblor shook the stadium at Oklahoma State University in Stillwater just at the end of the school’s football game with Kansas State. Number 3 ranked Oklahoma State’s players were gathered in the locker room under the Boone Pickens Stadium stands just after a 52 to 45 win against Number 17 ranked Kansas State when the ground began to shake. “Coach Mike Gundy was talking to me, everybody was looking around and no one had any idea,” quarterback Brandon Weeden said. “We thought the people above us were doing something. I’ve never felt one, so that was a first.” The shaking could be felt in the stadium’s press box for the better part of a minute before it subsided. The stands were already clearing out when the quake happened, just a few minutes after the down-to-the-wire game had ended. “That shook up the place and had a lot of people nervous,” Oklahoma State University wide receiver Justin Blackmon said. “Yeah, it was pretty strong.”
The 5.6M quake was the strongest every felt in Oklahoma, using records that go back 129 years. A 5.5 magnitude earthquake struck El Reno, just west of Oklahoma City, in 1952 and, before Oklahoma became a state in 1907, a quake of similar magnitude 5.5 struck in northeastern Indian Territory in 1882. The Saturday night quake was felt as far away as Tennessee and Wisconsin.
Some in Oklahoma reported cracks appeared after the latest quake. “There’s a crack going from the closet to the ceiling. I’ve never seen that before. I was in my bedroom grabbing my phone and I happened to notice it,” said Todd McKinsey, in the community of Moore, speaking with The Oklahoman Newspaper. Saturday’s earlier temblor, which hit at 2:12 a.m., woke people and pets as it shook an area that stretched from Texas to Missouri. The 5.6M tremor was felt over a much wider area.
Allegations have been made that the cause of the Oklahoma’s earthquakes is due to Hydraulic fracturing. Hydraulic fractures may form naturally, as in the case of veins or dikes, or may be man-made in order to release petroleum, natural gas, coal seam gas, or other substances for extraction, where the technique is often called fracking or hydrofracing. This type of fracturing, known colloquially as a frack job (or frac job), is done from a wellbore drilled into reservoir rock formations. The energy from the injection of a highly pressurized fluid, such as water, creates new channels in the rock which can increase the extraction rates and ultimate recovery of fossil fuels. The fracture width is typically maintained after the injection by introducing a proppant into the injected fluid. Proppant is a material, such as grains of sand, ceramic, or other particulates, which prevent the fractures from closing when the injection is stopped. There have been previous cases where seismologists have suggested a link between hydraulic fracking and earthquakes; however, data was limited so drawing a definitive conclusion was not possible for those cases.
The practice of hydraulic fracturing has come under scrutiny internationally due to concerns about environmental and health safety, and has been suspended or banned in some countries, however, the United States is not one of them.
It is important to remember that the magnitude scale compares amplitudes of waves on a seismograph, NOT the STRENGTH (energy) of the quake. Therefore, a 5.6M is 7.9 times bigger than a 4.7 as measured on seismographs. However, it is 22.4 times stronger. Since it is the energy or strength that knocks down buildings, this is really the more important comparison. This means that it would take 22, 4.7 magnitude earthquakes to equal one 5.6 magnitude tremor. Put another way, the 5.6M was 2,240% stronger than the 4.7M!
The Master of Disaster