The Sandwich Fault Zone is a

fault zone In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

that runs northwest from Oswego to

Ogle County Ogle County is a county in the northern part of the U.S. state of Illinois. According to the 2010 United States Census, it had a population of 53,497. Its county seat is Oregon, and its largest city is Rochelle. Ogle County comprises Rochelle, ...

, transecting Lee County in

Northern Illinois Northern Illinois is a region generally covering the northern third of the U.S. state of Illinois. The region is by far the most populous of Illinois with nearly 9.7 million residents as of 2010. Economics Northern Illinois is dominated by t ...

. The fault has generally not been active, although there was a minor earthquake in 2002, and another, slightly larger one, in 2010. It has a largely 400 to 600-foot vertical displacement, although parts can reach up to an 800-foot displacement, and is likely a configuration of several smaller faults, varying in both direction and displacement.

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References

* Geology of Illinois Geography of DeKalb County, Illinois Geography of Kendall County, Illinois Geography of LaSalle County, Illinois Geography of Lee County, Illinois Geography of Ogle County, Illinois Sandwich, Illinois Faults (geology) {{US-geology-stub

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