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Last modified at 11:29 p.m. on Sunday, March 18, 2001

Geologist studies Kansas quakes
KSU researcher monitors Humboldt Fault in Kansas.

By MATT MOLINE
Special to The Capital-Journal

MANHATTAN -- Veteran earthquake researcher Stephen Gao likes to stay close to the seismic action.

A decade ago, Gao lived in southern California, one of the world's most active earthquake zones, while completing a doctoral degree in geology at the University of California, Los Angeles.

Gao joined the faculty of Kansas State University in 1999 as assistant professor of geology.

Although Gao no longer lives and works in the shadow of California's infamous San Andreas Fault, he continues to monitor seismic activity in an unlikely place -- eastern Kansas' less-well known Humboldt Fault Zone.

"Studying earthquakes here is not like looking for tornadoes," Gao said. "You don't go out and chase one down. But you can record them."

As Kansas' leading quake recorder, Gao has had plenty of earthshaking news to send back to colleagues in California.

During the past six months, nearly 50 small "microearthquakes" have been detected in the vicinity of the Humboldt Fault line and neighboring seismic zones in the Sunflower state, Gao says.

"The majority of Kansas people have no idea about the earthquake potential in this area," Gao said.

Most of the recent Kansas temblors probably went unnoticed by humans, Gao says, and none measured above a 2.0 on the Richter Magnitude Scale.

In comparison, last month's quake that caused significant structural damage in the Pacific northwest registered a 6.2 on the Richter scale, the standard scale for measuring earthquake intensity since 1935, Gao said.

Kansas' Humboldt Fault is a 300-million-year-old subterranean fracture in a vast plate of granite stretching from Nemaha County on the north to Sumner County at the Oklahoma line.

In the Manhattan area, the Humboldt Fault is broken by series of bisecting underground fissures, a possible explanation for a series of recorded quakes that have topped out at 5.5 on the Richter scale in Pottawatomie and Riley counties.

An 1867 temblor centered between Wamego and Manhattan cracked plaster walls and demolished chimneys in both communities, while knocking a horse to its knees in Louisville, according to newspaper accounts.

"In reality, we really have no idea about the current stress field beneath us in Kansas," Gao said. "In California, maybe we can have some idea because people spend millions of dollars studying the San Andreas Fault. But here, we do almost nothing."

Geologists theorize that earthquakes erupt along fissures deep within the Earth's crust, sending violent vibrations to the surface, occasionally inflicting catastrophic damage to man-made structures, while killing or injuring thousands of people.

Gao's recent Kansas quake data has been gathered by a network of eight portable seismographs that were installed last summer throughout northeast and north central Kansas, and funded by a $46,000 grant from the National Science Foundation.

Last month, KSU's department of geology installed a new permanently-mounted $40,000 seismograph on campus, funded by a combination of public and private resource monies, Gao said.

Geologists at the Kansas Geological Survey office in Lawrence estimate that the Humboldt Fault is capable of producing a 6.5-magnitude quake every 2,000 to 5,000 years, said University of Kansas seismologist Don Steeples.

"In geologic time, that's a long period to wait for a return event," Steeples said. "The fact of the matter is, we don't know when the last 6.5 occurred. So the next one could be 10 years from now, or in 10 days. In any case, it will be a major event, the Kansas version of 'the big one.' "







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