We introduce the use of prototype point patterns to characterize the behavior of a typical aftershock sequence from the global Harvard earthquake catalog. These prototypes are used not only for data description and summary but also to identify outliers and to classify sequences into groups exhibiting similar aftershock behavior. We find that a typical shallow earthquake of magnitude between 7.5 and 8.0 has five aftershocks of magnitude at least 5.5, and these aftershocks are roughly evenly distributed in logtime between 0.113 days and 2.0 years after the mainshock. The relative magnitudes and distances from the mainshock for the typical aftershock sequence are characterized as well.

This work discusses computational problems related to the implementation of Victor and Purpura’s spike time distance metric for point processes. Properties of the metric and extensions of its use are investigated. These extensions include prototype point patterns that can be used for describing a typical point pattern and various clustering algorithms that can be applied to point process data through use of spike-time distance and prototype patterns.