The Earth's deep interior remains a major scientific frontier that holds the key to understanding the origin of the planet, its evolution through geologic time to the present structure, and the internal causes of plate dynamics, earthquakes, volcanism, and the geomagnetic field. Inaccessible to direct observation below a few kilometers (the limit of drilling and exposure by erosion) the Earth's crust, mantle, and core are primarily studied through their interaction with seismic waves. Recent developments in seismic sensor design, digital data acquisition, transmission, and storage techniques make possible dramatic improvements in the resolving power of seismic imaging methods. The Incorporated Research Institutions for Seismology, or the IRIS Consortium, is composed of 70 U.S. universities with research and teaching programs in seismology. It serves as a national facility for the development, deployment, and support of modern digital seismic instrumentation, and its mission is organized into three major program elements: (1) The Global Seismographic Network (GSN) program provides the U.S. contribution to an international network of 128 permanent, standardized, very-broad-band (VBB), wide dynamic range digital seismic stations at a spacing of approximately 2000 km around the globe. (2) The Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) aims to establish a U.S. national resource of 600 portable seismometer systems available for field deployment in specific seismic imaging experiments and for rapid response to earthquake studies. (3) The IRIS Data Management System (DMS) aims to provide the national and international seismic research community with timely access to data from the GSN and PASSCAL programs. It archives and distributes the data from these programs and facilitates the standardization and exchange of data. During its initial five years of operation from 1986 to 1990, the IRIS Consortium accomplished the following specific tasks: (1) It developed the IRIS-1 and IRIS-2 lines of standardized permanent station instrumentation employing VBB sensor technology for the GSN. Two IRIS operations and maintenance facilities for the GSN were installed at the U.S. Geological Survey's Albuquerque Seismological Laboratory and at the University of California, San Diego. Currently, 25 GSN VBB stations have been installed world- wide and are returning data. (2) The PASSCAL program has developed two lines of standardized portable seismographic instrument packages. One hundred of these are currently housed at the first PASSCAL Instrument Center, located at the Lamont-Doherty Geological Observatory. PASSCAL instruments have already been used in a number of planned field experiments, and were rapidly deployed for aftershock studies of the 1987 Armenia and 1989 Loma Prieta, California earthquakes. (3) The DMS has established GSN data collection nodes at the Albuquerque Seismological Laboratory and at the University of California, San Diego. An IRIS central data archive and distribution center is temporarily operating at the Center for High Performance Computing at the University of Texas. Through Internet, U.S. users (and European users via the ORFEUS data center in the Netherlands) have access to the continuous data streams from most of the existing GSN stations, to major-event waveform data in near-real time, and to special datasets from important earthquakes as well as from PASSCAL field experiments. This award provides FY-1991 funding for the participation of the U.S. Geological Survey's Albuquerque Seismological Laboratory in establishing the IRIS Global Seismographic Network and for related data management activities.
