Earthquakes are an unfamiliar phenomenon in Delaware. Because of the great public and scientific interest in the seismic events that have recently affected northern Delaware, this Open File Report has been prepared to present currently available information concerning the earthquakes and the investigation pursued by the Delaware Geological Survey. This is not a final scientific explanation of the events. To many persons it is shocking to realize that the earth that they regard as stable is, in fact, an active body. The present earth is a product of 4.5 billion years of history, during which time most geologic forces have acted so slowly as to be almost imperceptible. Therefore, sudden movements are disturbing. Earthquakes are the vibrations caused by relatively sudden slippage of deeply buried rocks. Earthquakes occur in a vast range of sizes; many are too small to be felt and others cause great damage. The events in Delaware that are described on these pages were relatively small and, although they warrant further study, which may lead to some precautionary measures, they do not represent cause for alarm.