The advances made by each of these professions depends on basic scientific research, on applied research founded on a clear understanding of what has happened after each earthquake, on collaboration to determine how best to improve the processes they use, and on education to disseminate best practices to all practitioners in each profession. The significant advances that have been made over the past 50 years have been aided by the availability of seismic monitoring data—records of earthquake events recorded by weak and strong motion instruments. All components of the built environment—buildings, bridges, roads, utility networks, and dams—share in the benefits. The records obtained have contributed to seismic hazard maps, to building codes and loss estimation programs, and to innovative emergency response tools that graphically display the areas subject to greatest damage.

In this process, it has become clear that earthquakes are very complex phenomena, each one leaving a different signature of ground shaking that varies in intensity and characteristics depending on location, ground conditions, type and geometry of faulting, and magnitude. Seismic monitoring holds the key to understanding both the seismic hazard and the response of the built environment so that proper preparations can be made for the future. However, despite the widely appreciated benefits of seismic monitoring data, we currently have in place only a fraction of the modern instruments needed to capture the essence of the earthquakes that are occurring. In fact, over the last 30 years in the United States, a number of opportunities have been missed to record events, yield new insights, and eventually reduce the cost of earthquakes.

The Advanced National Seismic System (ANSS) is envisioned as a state-of-the-art network of seismic monitoring instruments that will provide data on both earthquake occurrence and infrastructure response to earthquake ground shaking. The national benefits of such a system are easy to appreciate from a qualitative perspective; however, the benefits are inherently very difficult to quantify in terms of dollars “saved” or losses avoided. The ANSS was proposed by the U.S. Geological Survey (USGS) in 1999 and was endorsed by Congress in 2000 with the passage of Public Law 106-503. To the broad community with responsibility for reducing the effects of damaging earthquakes, this proposal represented a major step forward that would eventually lead to significant improvements in hazard assessment, structural engineering, loss estimation, and emergency management.

The past several decades have seen increased requirements from funding organizations for scientists to demonstrate not only that they are engaged in adding to the body of scientific knowledge, but also to demonstrate that scientific endeavors will ultimately provide tangible—and preferably quantifiable—economic benefits to the nation. It is in this context



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