The U.S. magnetic-anomaly data base is a national resource that is fundamental to geoscience investigations by providing key geologic, tectonic, and thermal information. These data are often needed to define geologic features hidden below the veneer of soil, water, vegetation, and urban development, which covers nearly three-quarters of our country. However, the U.S. magnetic-anomaly data base is largely inadequate to address many of our country's immediate concerns to know more about our planet's crust. A clear need to upgrade the U.S. magnetic-anomaly data base was strongly expressed by about 90 leading geomagnetists at the NRC/NAS U.S. Geomagnetic Initiative Workshop, convened in 1992 to determine the critical directions and the rationale for the advancement of geomagnetic research. The need for more accurate and reliable data was also expressed in responses to a questionnaire (Appendix 1) that was sent to state geologic surveys and professional geoscience societies and to program managers of the federal and private sectors.
The primary goal of improving the U.S. magnetic-anomaly data base is to provide reliable data that can be used to help resolve societal and scientific investigations of national importance involving the nature, composition, and processes of the Earth's crust. An additional reason to upgrade the data base is the international effort to compile an enhanced North American magnetic-anomaly data base. The North American compilation is critical in understanding regional geologic features that cross national boundaries. Unlike many developed and some undeveloped countries, the United States never supported a national program with the primary objective to systematically acquire magnetic-anomaly data. Consequently, the quality of the U.S. data falls below acceptable standards for most applications. Given the current advancements in the quality and coverage of magnetic-anomaly data in Canada, Mexico, and the Arctic region, an upgrade of the U.S. data is warranted for the forthcoming compilation of the magnetic anomaly data base of North America.