Ranking States by Seismic Activity

Abstract

Frequently, one sees comparisons and rankings of the various states. Perhaps it is interesting to compare the states by numbers of earthquakes. The main value of such a ranking is to provide an additional means to convey the importance of earthquake hazard awareness to the general population and to motivate earthquake preparedness and mitigation in the more active states. We consulted the catalog of earthquakes compiled by the Advanced National Seismic System (ANSS) and made available through the Northern California Earthquake Data Center (http://www.ncedc.org/anss/catalog-search.html). The catalog contains data from 1898 to 2005. Earthquakes in the catalog with magnitude 5.0 or greater are shown in figure 1. The ANSS catalog has varying levels of completeness, and most regions do not have earthquake entries going back to 1898. To compensate for incompleteness at the larger magnitudes, we supplemented the ANSS catalog with the catalog of significant U.S. earthquakes (1568–1989) available from the U.S. Geological Survey on the World Wide Web at http://neic.usgs.gov/neis/epic/epic.html. This extends the seismic history at the larger magnitudes. It is beyond the scope of this paper to seek out and incorporate regional studies that might provide a higher level of completeness, so the ranking in table 1 and the curves in figure 2 are limited to what can be inferred from the ANSS and USGS catalogs. We will address the issue of catalog completeness later. Figure 1. Epicenters of earthquakes with magnitude 5.0 or greater, 1755–2005, based on the ANSS seismicity catalog (http://www.ncedc.org/anss/catalog-search.html) and the USGS Catalog of Significant Earthquakes after 1769 (http://neic.usgs.gov/neis/epic). We also have edited in the 1755 Cape Ann earthquake. View this table: TABLE 1 Numbers of earthquakes, by magnitude, in the 10 most active states based on the ANSS catalog (1898–2005) and Significant U.S. Earthquakes (1568–1989) . * For those states that have coastlines, this table includes earthquakes up to …