Quake caused ground surface upthrow
An expert says Saturday's earthquake in Nagano Prefecture in central Japan caused the ground near the center of the quake to thrust upward by nearly 1 meter, leaving long bumps in the ground.
Professor Shinji Toda of Tohoku University has been studying the effects of the quake on the ground surface in Hakuba Village in Nagano, near the quake's epicenter.
The intermittent linear-shaped bulges are roughly 2 kilometers long and run north to south.
The ground on the eastern side of the bulges juts over the western side. The largest height difference is about 90 centimeters. The bumps can be clearly seen on roads and in rice paddies.
Toda says the bulges are evidence of slippage in the northern part of a fault in the Itoigawa-Shizuoka tectonic line fault zone.
The professor says the quake's shallow focus, estimated at around 5 kilometers underground, caused a relatively large slip on the ground surface, given the size of the quake.
He advises caution for further aftershocks and says more data are needed to see how the quake is affecting other faults in the fault zone.
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