Multitude of major earthquakes powerful, but not out of ordinary

KU's quake expert says recent tremors do not buck trend

With major earthquakes reported in Chile, Haiti, Indonesia, China and southern California and Mexico this year, earth scientists continue to hear the question: is it unusual?

The short answer is no.

Don Steeples

Don Steeples, the McGee Distinguished Professor of Applied Geophysics and senior vice provost for scholarly support, said anywhere from 15 to 20 earthquakes with a magnitude 7 or higher occur annually throughout the world. Thousands more occur with magnitudes in the 4 or 3 range and a more than a million are recorded annually that are rarely felt by humans.

Steeples has researched earthquakes in Kansas and elsewhere. He is internationally known for near-surface, high-resolution seismic reflection research that has been employed for many shallow-subsurface investigations. Practical applications of his work range from mapping bedrock and detecting faults at potential construction or drilling sites to what Steeples has described as the Holy Grail of near surface geophysics: locating clandestine cavities of interest to border authorities.

“There are two things to look at with recent earthquake activity,” Steeples advised. “One is that unnecessary concern and loss of sleep on the part of the public is not healthy, given the amount of misinformation or partial information that is out there.”

Second, news of natural disasters can serve to increase the awareness of policy makers, engineers and architects of the need to be prepared for a potential occurrence or reoccurrence.

The 7.7 magnitude earthquake in Sumatra, Indonesia, and the 7.2 magnitude earthquake this month in Baja California, Mexico, occurred in areas with active faults. Scientists are working to determine which fault produced the Easter Sunday earthquake that was widely felt in southern California and parts of Arizona.

Steeples noted the 8.8 magnitude earthquake in Chile on Feb. 27 was significant in that it was the fifth largest recorded in the world since 1900 and it shifted the Earth’s axis by a tiny amount. It was far more powerful than the magnitude 7 earthquake in Haiti on Jan. 10. Chile, which was also the site of the world’s largest recorded earthquake, a 9.5 magnitude in May 1960, was better prepared.

Movement in the Earth’s crustal plates cause a majority of earthquakes, especially along the rim of the Pacific Ocean. Haiti’s earthquake occurred along an area where the Caribbean plate separates from the North American plate.

Closer to home, ancient rifts below the Mississippi River Valley may account for an earthquake zone named for the southern Missouri town of New Madrid. From December 1811 through February 1812, four powerful earthquakes in the New Madrid area produced seismic waves that were felt from Canada to the Gulf of Mexico and from the Rocky Mountains to the Atlantic coast. The force of these earthquakes formed lakes in Arkansas and Tennessee, toppled chimneys in Cincinnati and St. Louis and rang church bells in Boston.

Estimated to be comparable in magnitude to the recent earthquakes in Haiti and Mexico, the New Madrid series set a record for the size of the area shaken in the United States and continue to rank among the largest in the lower 48.

Geologic evidence, Steeples noted, indicates that an earthquake of about magnitude 7 occurs in the New Madrid zone about every 400 to 600 years.

“It’s been 200 years since the last time an earthquake of that magnitude occurred,” Steeples said. While an earthquake in the magnitude 6 range could occur at any time around New Madrid, he points out that, “an earthquake in low 6’s might topple chimneys and knock dishes from shelves, but it isn’t going to destroy Memphis or St. Louis.”

Although a New Madrid earthquake could do minor damage along the Kansas-Missouri borders, events are rare. A more frequent source of earthquakes in Kansas is the Humboldt fault that runs from near Omaha to about Oklahoma City. In April 1867, an earthquake estimated to be about a 5.5 magnitude near Wamego, east of Manhattan, toppled chimneys, cracked plaster and was felt as far away as Dubuque, Iowa.

From 1977 to 1989, Steeples recorded more than 200 small earthquakes in Kansas and Nebraska. His research was initiated by a request by the Nuclear Regulatory Commission during the 17 years that Steeples was with the Kansas Geological Survey.

Steeples’ seismic data combined with the historical records indicate that a 6 or 6.5 magnitude earthquake in north central Kansas could occur once in about 2,000 years. Scientists don’t know when the last earthquake of a magnitude 6 occurred in this area.

“An earthquake of that magnitude would affect a big area, 10 to 15 counties in a fairly major way,” Steeples notes, given the population of the area now.

The seismic data and new evidence of California dam failures in earthquakes prompted a $175 million seismic stabilization project on Tuttle Creek dam north of Manhattan completed last fall.

Because no seismic record exists of the 1867 earthquake, Steeples has the distinction of recording the biggest earthquake in Kansas. It was a 4.0 magnitude in 1989 near his hometown of Palco in Rooks County, northwest of Hays. Steeples, who farms more than 2,000 acres with his brother, David, of Stockton, regularly makes the four-hour drive from Lawrence to Palco during planting and harvest seasons.

On a June 1989 trip to Palco, he packed along a portable seismograph and set it up before turning in for the night. A rumble woke him the next morning. “I knew immediately that it was aftershock — I could hear the needle wiggle back and forth on the seismograph paper in the next room.”

A 2008 Kansas Alumni magazine story profiling Steeples dubbed him the “Master of Disaster.” Although he works more closely with graduate students in KU’s geophysics program, Steeples is widely known among undergraduates for teaching a basic geology course “Earthquakes and Natural Disasters.” The class enrolls more than 650 a semester. Since his appointment as a vice provost in 2003, he teaches the class every third or fourth semester.

Steeples designed the course to teach earth science by focusing on natural disasters — earthquakes, volcanoes, tornados, hurricanes, floods, drought, wildfires and meteorite strikes. In addition to understanding the geophysical causes of disasters, students focus on how to mitigate their impact. On the first day of class, Steeples counsels: “I can guarantee that some of you in the next five or 10 years are going to be in some type of disaster. If you pay attention, this class will help you know what to do.”

Asked whether Kansas and Missouri residents should be more concerned about an earthquake or a tornado, Steeples responded wryly, “I tend to have more concerns about the economy than immediate worries about an earthquake in New Madrid or for that matter a tornado.”

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