Oberlin sits on fault line, quake expert says
By Ariella Cohen

Geology 110 and action-thrillers set in California teach that most earthquakes occur west of the Rockies, where the edges of tectonic plates scrape against one another and create intense friction that periodically must be relieved through seismic motion.

Earthquakes that occur far from plate boundaries puzzle geologists. But US Geological Survey seismologist David Boore, who demonstrated a new earthquake modeling system Tuesday, March 9, has found that historical data can be used to predict this more enigmatic breed of earthquake associated with mid-America.

Boore came to Oberlin last Tuesday to demonstrate a new modeling system able to predict ground motion and plot possible earthquake paths.

Boore’s model simulates an earthquake’s path by reproducing the sequences of large recorded earthquakes and simulating pattern movement using mean data of location, size and frequency. The model has been acclaimed for predicting recent ground motion along the New Madrid Fault, a fracture that ruptured most famously in 1811.

In 181l, the current of the Mississippi River reversed. Houses and riverbanks collapsed. The quake, estimated at over 8.0 on the Richter Scale, was 10 times stronger than the quake that devastated San Francisco in 1906. Boore’s plotting shows Oberlin along the 190 mile New Madrid Fault left in its wake.

“As soon as I got here I plugged in Oberlin’s latitude and longitude and found that the 1811-1813 earthquakes of New Madrid Mississippi left a consistent pattern of stresses on the tectonic plate where the town is situated,” Boore said. “If the plate is weak then a rupture could occur.”

Northeastern Ohio has experienced at least 20 felt earthquakes since 1836. While most of the quakes rate low on the Richter scale, there have been a few of considerable intensity over the past two decades. Falling between two historic earthquake epicenters or what Boore calls “bulls-eyes,” Oberlin is located within a cluster of hazard triangles, a vast geographic background zone where an earthquake could occur.

A low-intensity earthquake hit southeast of Oberlin in Ana in 1981, while a medium-intensity earthquake shook Perry in 1952 and again in 2003.

Immediately after the June 30 earthquake, a nuclear plant in Perry underwent an emergency inspection. No damage was discovered and the plant quickly reopened. Yet the quake’s close proximity to a nuclear power plant raised public awareness about hazard safety in regions not traditionally regarded as hazard zones.

Geology professor Bruce Simonson has felt four earthquakes in Oberlin since arriving in 1979. “They were all fairly small, but one did wake our technician who was napping in Kipton at the time by rattling the glassware,” Simonson said.

While a few lab assistants may have been jolted awake in recent years, the plotted pattern indicates at least half a millennium before another earthquake of significant specter.

“They haven’t been able to find any faults east of the Rockies that they are sure to be active but it is irresponsible to assume that the quakes are turned off,” Boore said. “The hazard maps that plot ground motion help engineers come up with provisions for building codes and seismic safety provisions.”

In his 33 years at City Hall, Oberlin Codes Administrator Marshall Whitehead has not heard much about earthquake safety. “I haven’t gotten the feeling that earthquakes were much of a threat, but it’s hard to predict Mother Nature,” Whitehead said.