Earth Sciences 1022A/B Lecture 10: Earth Science Lecture February 9 2016

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 1022A/B
• Professor: Stephen R Hicock

Document Summary

Mainly by elastic rebound of the crust as stress builds up. Rocks bend then eventually rupture at the hypocentre and energy radiates un all directions: then the cycle starts over as rocks start bending again. Foreshocks and aftershocks and aftershocks accompany the main event with some earthquakes. Uses tremor-detecting seismographs to record vibrations as surface waves and body waves that travel through rock: surface waves. Slowest, long l waves that travel in the surface like ripple on water: compressional. Faster, primary p waves travel in the direction of initiation: shear. Slower, secondary s waves travel perpendicular to the direction of initiation. Differences in arrival times of p and s waves yield wave travel distance from the epicentre: plot these distances from 3 stations as arcs in a map. Their intersection gives the location of the epicentre. Seismic station data indicate that earthquakes occur mainly at plate boundaries.