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 support for IRIS activities in 1991-1995. During this period IRIS will: -- Install an additional 50-60 stations of the GSN, bringing the total IRIS GSN stations to 75-85 (completion of the planned 128-station global network will be achieved with additional stations contributed by IRIS' international partners in the GSN and coordinated by the internationally organized Federation of Digital Seismograph Networks). -- Purchase an additional 500 PASSCAL portable seismographic units of standard IRIS design and manage their deployment and maintenance for the seismology research community through the establishment of two additional PASSCAL Instrument Centers to be located at U.S. universities. -- Install and develop to full capacity a permanent Data Management Center (DMC) to be located at a U.S. university. The five-year objectives of the DMC include complete archiving of the world-wide continuous VBB data, very rapid turnaround of customized datasets to the international seismology community, and improvement of current capabilities for managing data from PASSCAL one- and two- dimensional array field experiments. -- Assume a leadership role in reaching out to the science community regarding the use of IRIS facilities in earth sciences research by sponsoring an annual science planning workshop. IRIS will also formulate and implement a plan for the use of PASSCAL instruments in rapid response to earthquake prediction and aftershock monitoring needs. -- Create an inexpensive version of the portable PASSCAL instrumentation with coordinated educational materials that will permit low-cost high-school involvement in seismic monitoring, and develop an educational state-of-the-art traveling museum exhibit of a complete seismographic station, with direct real-time connection with the IRIS Data Management Center.
