Small Earthquake Registered At Mount St. Helens With AM-Earthquake
Oct. 02, 1987
SEATTLE (AP) _ A small earthquake shook the Mount St. Helens area Thursday evening, 13 hours after a powerful temblor caused widespread destruction in Southern California, officials said.
The temblor hit the volcano area at 8:38 p.m. and registered about 2.5 on the Richter scale, said University of Washington seismologist Linda Noson. She said the quake was not linked to volcanic activity, and added that further details would be unavailable until Friday morning.
At KOIN-TV in Portland, Ore., reporters said four or five calls about the tremor were received from residents in the Vancouver, Wash., area, across the Columbia River from Portland.
Southern California's quake measured 6.1 on the Richter scale and struck at 7:42 a.m.
Mount St. Helens first stirred to life in this century in March 1980. Its May 18, 1980, eruption leveled 230 square miles, left 57 people dead or missing and sent up an ash cloud that circled the globe.
The Richter scale is a measure of ground motion as recorded on seismographs. Every increase of one number means a tenfold increase in magnitude. Thus a reading of 7.5 reflects an earthquake 10 times stronger than one of 6.5.
An earthquake of 3.5 on the Richter scale can cause slight damage in a local area.