THE CRUX

THE LATEST SCIENCE NEWS AND NOTES

January/February 2019^ DISCOVER^9

DEADLY COMBINATION

In September, a 6.7-magnitude earthquake struck Japan’s northernmost main island, Hokkaido, including the town of Atsuma.

It couldn’t have come at a worse time. Only days before, Typhoon Jebi had soaked the area, where the soil has a loosely

structured layer of volcanic ash. The intense precipitation increased the water pressure within the soil, which can trigger

landslides, according to Kyoji Sassa, a Kyoto University expert in soil mechanics. Another trigger? Shear stress — the parallel

stress applied to a surface — caused by earthquakes. Atsuma experienced both, causing this catastrophic collapse in a matter of

hours. The devastation visible throughout this image stretched for several square miles. According to Japan’s Fire and Disaster

Management Agency, 41 people died; 36 were in Atsuma.  ERNIE MASTROIANNI; PHOTO BY TAKESHI UEDA/KYODO NEWS VIA AP