The Importance of Small Earthquakes

Abstract

Regional and local seismic networks have become ubiquitous throughout the world to study local seismotectonics, to provide immediate hypocentral and magnitude information following felt or damaging earthquakes, to create ShakeMaps of the ground shaking due to earthquakes, and to form the sensing backbone of incipient early warning systems of earthquake shaking. They also provide data for earthquake forecasting research, nuclear test monitoring, and analyses of nonearthquake events such as explosions, intense storms, mine collapses, etc . Some seismic networks are aimed at detecting and recording seismic events down to the lowest possible magnitude, while others are strong-motion networks that aim to properly record the strongest possible ground shaking that can take place. Significant resources are invested annually in regional and local seismic monitoring, and such networks have become a permanent fixture in many areas of the world. Is it important to record and process seismograms of all earthquakes down to magnitude 3? Magnitude 2? Magnitude 1? Magnitude 0 or below? My purpose in writing this opinion piece is not to question the intrinsic need for regional and local networks. On the other hand, I do feel it is important that there should be a full and informed public discussion about the importance of the small earthquakes that we record. Is it important to record and process seismograms of all earthquakes down to magnitude 3? Magnitude 2? Magnitude 1? Magnitude 0 or below? Informed discussions on these issues sometimes take place when a decision must be made about a particular site, such as whether to put a high-level radioactive waste repository at Yucca Mountain in Nevada. But for the most part, regional and local seismic networks, once they have been initiated, tend to grow based on a “more is better” philosophy as funding is available. I believe that the existence and …