Mountain Collapses After Japan Earthquake

After an earthquake estimated at magnitude 7.2 on the Richter scale struck the rural areas of Tohoku, Japan on Saturday, citizens took comfort in the fact that the death toll was relatively limited given the magnitude of the disaster. The scale of damages other than human loss, however, is still staggering.

According to Japanese media, a mountain collapsed and disappeared completely in the city of Kurihara, Miyagi Prefecture, in the vicinity of the epicenter. Many roads and bridges are ruptured and destroyed. Casualties were mostly those who were at a construction site and unable to flee the collapsing building, or those who were behind the wheels and swept away by landslides. One victim was hit by a truck and killed after the tremor drove him out into the street.

At a mountain of Kurihara City, a landslide left seven people buried under the rubbles, including guests and employees of a hot spring inn. Three of them found dead at around 3 p.m. Sunday. A rescue mission is in progress for the rest.

In Oshu City, a bus with 20 passengers fell tens of meters down the cliff in landslides, but all of them were rescued safely by a Self-Defense Force helicopter immediately dispatched to the site.

The earthquake is a “shallow-focus earthquake” that creates vertical plate movements. Experts explain that the earthquake occurred when two plates met and a fault slid up. Yuji Yagi, an associate professor at Tsukuba University, said the fault line that caused the earthquake is about 30 kilometers long and 10 kilometers wide, and it moved for about 10 seconds, leaving a shear estimated to be 4 meters in some parts.

The magnitude of the tremor is the same as the Hanshin earthquake of 1995, which killed over 6,000 people, and bigger than the 6.8-magnitude Niigata earthquake last year that killed 15 and injured 2,300. Damage to facilities this time is much more limited: around 40 buildings or houses have been damaged so far. The Hanshin earthquake destroyed 250,000 houses, and Niigata 7,000.

Experts say that seismic waves need to last for 1.5 seconds to give substantial damage to facilities. The waves this time lasted for about 1 second. Also, the cold and snowy climate of Tohoku City and surrounding areas helped limiting damage. People in the region roof their houses with light iron plates to avoid snow pileups, and make windows or doors small to keep cold out.

Japanese law requires tough seismic design codes for all houses to withstand a tremor at magnitude 7.