Seismology is the study of stress and changes in stress within the Earth and other planetary bodies, particularly earthquakes caused by slip and rupture along faults and by magmatic activity. The field is also concerned with earthquake risks and hazards, as well as the propagation of elastic waves through the surface of the EarthSEISMOLOGY, the science of earthquakes, is primarily concerned with such questions as where, how and why earthquakes occur, but it is also concerned with the question how the waves generated by earthquakes travel through the earth, and with the question what information as to the constitution of the earth can be deduced from the behaviour of the waves. Living in a country which is seldom troubled by earthquakes, but a country in which the waves from distant earthquakes can be studied, we have a more direct interest in questions of the latter types.