Cracked earth mixed with rain: Recipe for landslides

JOHN DODGE, THE OLYMPIAN

OLYMPIA -- Heavy rain on the heels of Wednesday's major earthquake could be the recipe for increased landslides, a state geologist warned Thursday.

"It's one of the things to worry about," said Tim Walsh, a state Department of Natural Resources geologist. "Cracks in the earth could accumulate water and trigger landslides."

The immediate threat of a 2- or 3-inch downpour is not very great, National Weather Service meteorologist Bill Burton said.

"We're looking at a quarter- to half-inch of rain, then back to dry weather this weekend," Burton said.

Aerial surveys of South Sound after the 6.8 magnitude earthquake revealed very few ground disturbances, Walsh noted.

He said the dry winter helped the soils withstand the earthquake.

The earthquake epicenter 11 miles northeast of Olympia was also the scene of two minor aftershocks Thursday -- a magnitude 3.4 event registered at 1:10 a.m. and a 2.7 magnitude shaker at 6:23 a.m.

"Having aftershocks more than 12 hours after the earthquake is rare," he said.

Walsh confirmed the quake's location was in close proximity to the magnitude 7.1 earthquake that rumbled through the region on April 13, 1949.

It's in an area where the Juan de Fuca oceanic plate starts to descend more steeply beneath the North American continental plate more than 30 miles below the Earth's surface.

The earthquake occurred as the Juan de Fuca plate stretched in a downhill direction, sending shock waves to the Earth's surface that were felt as far away as Salt Lake City, he said.

"It was almost a twin of the 1949 earthquake," he said.

Homeowners also were warned Thursday to keep a close eye on large trees near their homes for possible root damage from the earthquake.

"It's a lot like after a windstorm -- look for cracking of the soil around the base of the tree," said Ron Schneider, owner of Ron's Stump Removal and Tree Service.

John Dodge covers the environment for The Olympian. He can be reached at 754-5444.

The Olympian Copyright 2000

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