Helens, Rainier are tops among most dangerous U.S. volcanoes

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Apparently in October 2006, seismologists say there was a slight scare caused by gaps in the coverage of the seismographs. A 4.5 magnitude earthquake was determined to have struck the eastern edge of the volcano. Based on the available seismograph data, it appeared that aftershocks were moving closer to the center of the volcano, a possible sign of bigger things to come. It turned out to be a "false clue" created by gaps in the network.