tional structures that are most effective in addressing the basic and applied problems of earthquake research. In particular, there is a critical need to maintain and expand scientific centers where the disciplinary activities of many research organizations can be coordinated, evaluated, and synthesized into system-level models of regionalized earthquake behavior. In addition to their key role in basic earthquake science, such multidisciplinary centers have proven to be effective organizations for the dissemination of earthquake information and research results, the formulation of science-based strategies for loss reduction, and the education of the general public and nonscientist professionals concerned with disaster mitigation and loss reduction.



The International GPS Service (IGS) is an International Service under the Federation of Astronomical and Geophysical Data Analysis Services. IGS has developed a worldwide system to put high-quality GPS data on-line within one day and data products within two weeks. The system consists of about 125 satellite tracking stations, 3 data centers, and 7 analysis centers. GPS data are used to generate GPS satellite ephemerides, Earth rotation parameters, IGS tracking station coordinates and velocities, and GPS satellite and IGS tracking station clock information. See < http://igscb.jpl.nasa.gov/>.


National Research Council, Basic Research Opportunities in Earth Science, National Academy Press, Washington, D.C., pp. 101-105, 2001.


For example, aseismic “silent earthquakes” have recently been observed on the thrust interface of subduction zones by geodetic networks in Japan and Cascadia, but the interplay between these events and major earthquakes in subduction zones is not understood; see Section 4.2.


E.H. Field and the SCEC Phase III Working Group, Accounting for site effects in probabilistic seismic hazard analyses of Southern California: Overview of the SCEC Phase III report, Bull. Seis. Soc. Am., 90, S1-S31, 2000.


A notable exception is the excellent data set collected by the Taiwan Central Weather Bureau from the 1999 Chi-Chi, Taiwan, earthquake (M 7.6).


See <http://www.trinet.org/shake/index.html>; <http://pasadena.wr.usgs.gov/shake/>.

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