Oklahoma rolling ‘n shaking Published April 24, 2009 By Steve Serrette 72nd Air Base Wing Safety Office TINKER AIR FORCE BASE, Okla., -- What is an earthquake? An earthquake (also known as a tremor or temblor) is the result of a sudden release of energy in the Earth's crust that creates seismic waves. At the Earth's surface, earthquakes manifest themselves by shaking and sometimes violent movement accompanied by displacement of the ground. It is a natural phenomenon that results from underground movement along a fault plane. You may think that because we live in Oklahoma that tornadoes are the most violent natural phenomena we have to deal with and that we are somewhat immune from earthquakes. Not so. Oklahoma has many earthquakes that go unnoticed every year because they are so small, said Kenneth Luza, an engineering geologist at the Oklahoma Geological Survey in Norman. "The average magnitude for an earthquake in Oklahoma is around 2.4, which is a very small earthquake," Mr. Luza said. These earthquakes are not uncommon and are not a cause for alarm, he said. The largest earthquake in Oklahoma's history occurred in April 1952. It reached a magnitude of 5.5 and was felt from Des Moines, Iowa, to Austin, Texas. This earthquake caused moderate damage at El Reno, Oklahoma City and Ponca City, including toppled chimneys and smokestacks, cracked and loosened bricks on buildings, and broken windows and dishes. One crack in the state capitol at Oklahoma City was 15 meters long. Slight damage was reported from many other towns in Oklahoma and from some towns in Kansas and Texas. The earthquake was caused by slippage along the Nemaha fault. The Nemaha zone is about 400 mi in length, extending south-southwest from the "Nemaha Mountain Structure" in southeastern Nebraska and northeastern Kansas, across Kansas and northern Oklahoma, then south into central Oklahoma, where it splays out and terminates against the Oklahoma megashear in southern Oklahoma. The 1952 earthquake was felt over most of Oklahoma and in Arkansas, Iowa, Kansas, Missouri, Nebraska and Texas. The most recent earthquake on record occurred right here, this year in the Oklahoma City area March 8 at 8:06 a.m. at epicenter. It was felt in Midwest City, Del City and other surrounding areas. It measured 3.4 on the Richter scale. The tremor was at least the sixth earthquake people have felt in Oklahoma during 2009. Others were a 3.3-magnitude quake Feb. 24 in Pittsburg County, quakes of 3.2 and 3.4 on the Richter scale in Grady County on Feb. 22 and Jan. 28, a 3.2-magnitude quake Feb. 3 in Coal County and a 2.4-magnitude quake Jan. 29 in Lincoln County. One of the greatest threats during an earthquake is falling debris. Earthquakes are unpredictable and strike without warning. Therefore, it is important to know the appropriate steps to take when one occurs, and to be so thoroughly familiar with these steps, that you can react quickly and safely. If you are in a commercial or residential building, remember the following procedures. Steps to take during an earthquake: · Remain inside the building. · Seek immediate shelter under a heavy desk or table --or brace yourself inside a door frame or against an inside wall. · Stay clear of windows -- at least 15 feet away. · Stay put. If shaking causes the desk or table to move, be sure to move with it. · Resist the urge to panic. Organize your thoughts. Think as clearly as possible, and anticipate the sights and sounds that may accompany an earthquake. · Don't be surprised if the electricity goes out, fire or elevator alarms begin ringing, or the sprinkler system is activated. · Expect to hear noise from broken glass, creaking walls and falling objects. Steps to take immediately after an earthquake: · Remain in the same "safe" location for several minutes after the earthquake, in case of aftershocks. · Do not attempt to evacuate or leave your immediate area unless absolutely necessary or when instructed to do so by a proper authority. · Check for injuries and administer necessary first aid. Recognize and assist co-workers who are suffering from shock or emotional distress. · Implement your survival plan. Establish a temporary shelter (shelter-in-place) if rescue teams are expected to be delayed. · Use a stairway when instructed to exit building.