1. Introduction. 2. Earthquakes, Why and Where do They Occur? 3. Structure of the Earth's Interior. Crust. Mantle. Core. 4. Seismic Waves. Basic types and essential properties. Propagation paths. 5. Travel Times. 6. Seismographs and Seismological Observatories. General considerations. Recording systems. Instrumental frequency characteristics. Analog and digital records. 7. Seismograms and Interpretations. Local and regional events. Volcanic earthquakes. Unusual seismic sources. Teleseismic events 10<&Dgr;<103°. Teleseismic events &Dgr;>103°. References. Subject Index. Geographical Index.