September 2015 – WASHINGTON – A 4.3 magnitude earthquake has hit the wildfire zone in north central Washington. The quake, which was six miles deep, hit 26 miles east of Okanogan and 25 miles north of Grand Coulee at 9:42 a.m. There are no reports of any injuries or damage. The dam, built between 1933 and 1942, was built to withstand large earthquakes, according to The Wenatchee World. A local engineer told the World that large concrete dams, such as the Grand Coulee, keep their shape and contain their reservoirs even in an earthquake measuring 8.0.
“In general, the dams are very, very robust,” Kevin Marshall at the Grant County PUD, told The Wenatchee World. “It’s not like a building. The building codes have you design a skyscraper so you can exit in a one-in-500-year event. We hold the dams to a higher standard. That ‘wall of water’ is a very, very low probability thing.” According to the Pacific Northwest Seismic Network and KIRO 7 meteorologist Morgan Palmer the 4.3 magnitude earthquake of that depth was considered shallow and was likely felt as a jolt. – My Northwest