When the earth shakes we may feel it, even in South Dakota

KELOLAND.com Original

SIOUX FALLS, S.D. (KELO) — The Upper Midwest doesn’t get many big earthquakes but even when a smaller one happens, we still may be able to feel it.

A 3.2 magnitude earthquake was reported Tuesday, Dec. 8, in Walworth County, northwest of Bowdle, according to the U.S. Geological Service (USGS). A 3.2 magnitude is described as a minor earthquake. It happened at just before midnight.

As of the morning of Dec. 10, the USGS reported 12 responses to its “Did You Feel Category” which invites the public to report if they felt the earthquake. The USGS data shows 12 responses and lists locations for 11 of them.

While South Dakota does not have earthquakes of the magnitude of California or Alaska, but because the geography of the state is older, the seismic effect can travel farther, said Kevin Ward, an assistant professor in the geology and geological engineering department at the South Dakota School of Mines and Technology.

The impact or feel factor would be mild with the 3.2 earthquake.

Those at the quake’s epicenter or near it, could have “mild shaking for dishes rattling in the home,” Ward said.

Yet because the geological makeup of South Dakota is older, is at a cooler temperature and dense, the quake could be felt at a distance from Bowdle, Ward said.

A feel it response was reported to the USGS from Grand Forks, North Dakota, about 207 miles away from the Dec. 8 earthquake. Ward said it’s possible someone felt it in Grand Forks but there is not enough evidence or statistical data to say for certain.

Responses ranged from 17 kilometers (10.5 miles) away in Bowdle to 333 kilometers (about 207 miles) away in Grand Forks. Six responses were from Beadle. Two were from Hosmer, 24 kilometers (about 15 miles) away. One was from Roscoe, 37 kilometers (about 23) away. One response was from Hoven, 38 kilometers (about 23 miles) away. One was from Grand Forks.

States in the northern Great Plains of the U.S., such as North Dakota, and adjacent provinces in central Canada (Manitoba, Saskatchewan) have experienced the fewest significant earthquakes in North America, according to a study by Kean University in New Jersey.

One of the state’s biggest earthquake recorded was a 4.5 quake that happened on June 2, 1911, according to the USGS. The map places the location between Huron and Mitchell, near the James River. The coordinates of the location are 44.200°N 98.200°W.

The USGS lists at least 40 earthquakes recorded in South Dakota or partially in South Dakota and Nebraska. The USGS lists 64 earthquakes with ties to South Dakota.

According to the University of Minnesota, the state has had 20 small to moderate earthquakes documented since 1860. The most recent was on April 23, 2011, in Brandon in Douglas County which registered at 3.12. The strongest was a 4.6 to 4.8 quake on July 9, 1975, near Morris in Stevens County.

On Sept. 28, 1964, an earthquake of 3.4 was documented at Pipestone.

Iowa was one of only four states that did not have an earthquake between 1975 and 1995, according to the Iowa Department of Resources. The largest Iowa earthquake happened Davenport in 1934, and Iowans felt the most recent quake southwest of Shenandoah in 2004, the DNR said in 2011.

About three years ago, on Aug. 15, 2017, there was a 3.0 earthquake 16 kilometers (about 10 miles) northeast of Onida, South Dakota, according to earthquake.com.

Scientists often refer to fault lines in areas where there are frequent earthquakes. Faults are a fracture or zone of fractures between two blocks of rock, the USGS said.

A hazard mitigation plan for the state of New York describes earthquakes as “both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip, or by volcanic or magmatic activity, or other sudden stress changes in the earth.”

Ward said there are three types of earthquakes: The two piece tower where rock thrusts forward at each other, the strike slip where there is only horizontal movement as rock slips past each other and the normal fault quake where two pieces of rock pull apart.

He suspects the Bowdle earthquake may be a normal fault quake.

Earthquakes recorded in South Dakota since 2000 include a cluster near or in the Black Hills area.

The Black Hills are a good example of an area created by earthquakes.

“All topographical lifts, each one is created by hundreds of thousands of earthquakes,” Ward said.

“There is a slightly higher risk for earthquakes in western and southwestern (South Dakota),” Ward said.

But there is no modern pattern for earthquakes in South Dakota, Ward said.

It’s possible earthquakes in the Black Hills area could be related to the structure from earthquakes that happened many, many years ago, he said.

As a scientist and researcher Ward’s focus is on earthquakes that happen in California, Alaska and the Cascade area of Oregon which all have larger magnitude earthquakes.

He’s working with a multi-layered group of hundreds researchers to develop an improved earthquake early warning system. His piece is to study the geography of earthquake areas, Ward said.

But, he is still curious about earthquakes in South Dakota.

Ward receives email alerts when large earthquakes such as those of 6 magnitude and higher happen around the world. South Dakotans can receive a similar email when earthquakes happen in the state by using this USGS website.

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