EESA06H3 Chapter Notes - Chapter 3: Subduction, Cascadia Subduction Zone, Pacific Plate
Document Summary
A single analog station could determine only the distance to a quake, not the direction. A circle was drawn on a globe, with the centre of the circle being the station and its radius the distance of the quake. With information from 2 or more stations they could pinpoint the location of the quake. If 3 or more stations determined the distance to a single quake, a circle was drawn for each station and the intersection of the circles located the epicenter. Modern 3-component seismographs now record the intensity of the earthquake vibrations in their 3 orthogonal directions. This allows scientists to determine both direction of the incoming wave and the distance from epicenter. Analyses of seismograms also indicate at what depth it occurred. Most quakes occur at the earth"s surface although a few occur much deeper. Maximum depth of focus is the distance between focus and epicenter for earthquakes is about 670 km.
