Searching for prehistoric earthquakes in lake sediments

Abstract

How often do major earthquakes occur? Do they follow regular patterns of recurrence, and if so, what is the length of the recurrence interval? These questions are of obvious importance to populations located in regions where earthquakes are a commonplace occurrence. They are also relevant questions in regions that are for the most part seismically inactive but that have experienced anomalous earthquakes of destructive force one or more times in recorded history. Also, what about areas that have never experienced an earthquake in historic times? Human history is short when compared to the geologic time scale. Is it possible that places which we regard as seismically inactive might actually have experienced a major earthquake in the recent geologic past? Historic records of earthquakes are too short to allow a true assessment of recurrence intervals; therefore, a method is needed that will enable the seismic history of a region to be exteneded beyond the limit of historic time.