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INTERNATIONAL ASPECTS Seismologists were aware very early of the need for data collection on a global scale. Therefore, in addition to organizing networks of stations, they developed various means for assembling and communicating data in various forms. The International Seismological Centre (ISC) in Great Britain, the Bureau Centrale Internationale Seis- mologique (BCIS) in France, and the U.S. Geological Sur- vey's National Earthquake Information Service (NEIS) are examples of centers that were created to systematically collect, process, and distribute earthquake data and hypo- center locations. This careful, comprehensive analysis of worldwide earthquake data has been and continues to be a powerful influence toward the excellence of past and present seismological research, and continued support for the work of these centers is needed. A glance at the map of station distribution (Figures 4 and l0) shows that the combined WWSSN and digital network would provide good, but not complete, worldwide coverage of stations. However, some large land areas in Canada and the Soviet Union, for example, are covered by networks of those countries, and while the networks use instruments different from the U.S.-supported networks, they are internally standardized and calibrated. Data from the Canadian net- work is often used to complement those of the WWSSN. Many seismological problems important to the United States require data on a global scale, and a strong pro- gram of data exchange with other countries is a necessity. This was an important consideration in the establishment of the WWSSN, and one of the greatest contributions of that network has been the enormous reduction in the time required for an investigator to obtain a set of seismograms for an event he has chosen to study. This service needs to be expanded through formal arrangements among national 46
47 networks, so that the seismograms of large numbers of earthquakes recorded at observatories distributed over much of the earth's surface can quickly be made available to scientists in all participating countries. One method of distributing data internationally from a relatively large network is that now used by the Canadians. Records from the Canadian national network are microfilmed by the Dominion Observatory, and a master microfilm copy is made available to the Environmental Data Service (EDS) in the United States. The EDS then makes copies of this micro- film on request, charging only the cost of copying. The U.S. Government pays no additional costs, and the cost of exchanging original seismograms is avoided. International cooperation in seismology is also fostered through the International Association of Seismology and Physics of the Earth's Interior (IASPEI) and its parent organization the International Union of Geodesy and Geo- physics (IUGG). Through the International Council of Scientific Unions (ICSU), of which the IUGG is a member, the World Data Centers (WDC's) were created during the International Geophysical Year (IGY). WDC-A is in the United States, WDC-B in the Soviet Union, and WDC-C in western Europe and Japan. Since l973, the WDC's have been acquiring and distributing copies of seismograms of im- portant earthquakes. The IUGG also joins with other major scientific unions for the development of international programs of mutual interest. A good example of such a program, of interest to seismologists, is the International Geodynamics Project (IGP), which is under the guidance of the International Geodynamics Commission (IGC). The Panel on Seismograph Networks has invited comment from IASPEI and its correspondents about the value of the WWSSN to the international seismological community and about ways in which the new digital-data-acquisition systems may benefit it. (See Appendix B.) The responses received over- whelmingly favor continued operation and improvement of the WWSSN, deployment of digital-recording systems, and development of a system for ready availability of digital data. It is worth emphasizing that the contribution to the WWSSN by the countries in which the foreign stations are located has been substantial, and, again, that U.S. support of foreign stations is fully justified in terms of the needs of American science. The accompanying benefit to international scientific progress is a highly desirable by-product.
48 Program of international exchange of seismological data have been essential to the success of seismological re- search from its beginning. The Panel recommends that such international coopera- tion and exchange be continued and expanded and that particular emphasis be given to the exchange of digital data to augment the proposed integrated global network.
