Great Earthquakes and Global Seismic Networks

Seismologists often jest that “the best way to stop earthquakes is to deploy seismic stations.” The laborious effort to install seismometers to record signals from earthquakes or to pursue targeted investigations of Earth's structure is sometimes confounded by the vagaries of earthquake occurrence, which is decidedly nonuniform in space and time. Of course, this often proves to be more of an anxiety than a reality, and most efforts, especially those employing multiyear installations, succeed in gathering valuable seismic data. One of the most gratifying examples of success is provided by the deployment of the Incorporated Research Institutions for Seismology–National Science Foundation–U.S. Geological Survey (IRIS-NSF-USGS) Global Seismographic Network (GSN) in parallel with numerous international deployments of broadband seismometers in the Federation of Digital Seismic Networks (FDSN). Between about 1982 and 2004, global installations of high-quality broadband digital seismometers proliferated, replacing the obsolete analog systems of the World-Wide Standardized Seismograph Network and upgrading sparse institutional observatories and first-generation digital networks. While deployments of important additional stations continue, by 2004 the GSN had achieved its basic design goals: openly available continuous broadband data from roughly 130 stations providing real-time global coverage and large dynamic range (Butler et al. 2004). Then the 26 December 2004 great Sumatra-Andaman earthquake ( Mw 9.2) occurred—the first event to exceed magnitude 9 since the 1964 Alaska earthquake. The GSN and FDSN provided unprecedented global seismic recordings for this event and enabled more detailed seismological investigation than was possible for any prior event of such size ( e.g. , Lay et al. 2005; Bilek et al. 2007). Those same globally distributed seismic stations have gathered data from a substantial number of great earthquakes; from 2001 to 2010, there have been 18 events with MS ≥ 8 and 13 events with Mw ≥ 8, whereas over the previous …