SEISMOLOGICAL CONSIDERATION F, October 8, 1968 INTRODUCTION Some of you may be surprised to hear me sey that the science of seismology is a relatively young science, even though observation of earthquakes and their effects has drawn the attention of man since the earliest civilization. We realize that until nearly the end of the nineteenth century data collected from earthquakes was mainly qualitative. Moreover, because of the spectacular nature of large earthquakes and their effects on human beings, these observations without instruments were unreliable and strongly colored with emotion. It is important to recognize that even now, in the twentieth century, popular accounts of earthquakes and their effects are not wholly reliable sources of information. The literature is full of interesting tales of seismic effects, some of which are legendary. Attempts to explain causes of earthquakes, even to predict them from these qualitative observations have led to widespread fallacies, superstitions and much folklore, THE SCIENCE OF SEISMOLOGY I make these preliminary remarks in order to give you some of the facts of seismology which have developed in the twentieth century. By systematic, scientific methods measurements have been made of the effects DOE ARCHIVE of earthquakes using highly specialized seismograph instruments, improved methods of data collection, processing and analysis. A result of these developments is a more reliable and comprehensive understanding of the mechanisms, not only of earthquakes, but also all other kinds of seismic disturbances. Zl