data, and then applied in earthquake engineering research and practice. As richer data sets are collected, a primary challenge will be to set up a computational framework for the systematic refinement of three-dimensional wave-speed and attenuation models and the use of these models in the calculation of synthetic seismograms. A consistent interface will be needed for coupling ground-motion calculations to nonlinear soil-modeling codes. Significant research is needed on how to use waveform modeling to characterize the probability distributions of ground-motion time histories, or parameters derived from those time histories, in a way that properly accounts for both aleatory and epistemic uncertainties.
The transition of earthquake science to a systems-oriented, physics-based approach has important ramifications for the types of cooperative research activities and organizational structures that will be most effective in addressing the basic and applied problems of earthquake research. In particular, additional support is needed for scientific centers and distributed collaboratories with advanced information technology infrastructures, where the disciplinary activities of many research groups can be coordinated, evaluated, and synthesized into system-level models of earthquake behavior. In addition to their key role in basic earthquake science, such centers have proven to be effective in disseminating earthquake information and research results, formulating science-based strategies for loss reduction, and educating groups at all levels about the role of science in disaster mitigation and loss reduction.
The technological investments and programmatic support required for earthquake research during the next 10 years will outstrip the resources currently available through NEHRP and other federal programs. Major initiatives by the two NEHRP science agencies illustrate this situation. The U.S. Geological Survey (USGS) has proposed the deployment of an Advanced National Seismic System (ANSS), which would upgrade the U.S. National Seismographic Network, modernize regional networks, and deploy 6000 strong-motion stations in high-risk urban areas. A fully implemented ANSS would upgrade regional networks to modern seismic information systems and provide the framework for developing real-time warning systems. The ANSS plan, if brought into full operation, would greatly improve seismological instrumentation in the United States and would contribute substantially to the objectives outlined in this report. This system will require capital investments of approximately $170 million, and its annual operational costs are estimated to be about $47 million. In comparison, the congressional appropriation for the entire USGS component of the NEHRP budget was only $50 million for FY 2001.