Peter M. Shearer is a Professor of Geophysics at the Scripps Institution of Oceanography, University of California, San Diego. He has written over one hundred scientific papers on various aspects of seismology and is currently the President-Elect of the seismology section of the American Geophysical Union. He has taught the introductory seismology class at Scripps for over 15 years; this book is based on material and problem sets that were developed for this class.