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to deal with such landslide disasters. The study, which was conducted by USGS geologists and hydrologists in cooperation with the city and county of Honolulu, developed new scientific techniques to analyze debris flows and landslides and methods of applying these techniques in ways that are helpful to local planners and officials. Debris-flow investigations focused on identifying when and where these rapid and potentially fatal slope movements are likely to occur and established the rainfall thresholds required to trigger them. These thresholds are now the basis for a public warning system like the one currently operating in the San Francisco Bay region. Areas susceptible to debris flows were mapped by using a newly developed computer-based digital method. Information on volumes, travel characteristics, and more than 1,500 source locations of past debris flows was combined to create computer models of potential debris flows that were routed through a digital model of the landscape. The computer generated numerous such simulations in order to systematically delineate areas of hazard. In combination with the rainfall thresholds, the resulting hazard-zone map, released in FY 1993, provides local officials with information needed for effective planning and emergency response over a 180-square-kilometer (70square-mile) area around Honolulu.

The USGS Landslide Hazards program seeks to reduce landslide losses that occur throughout the United States by:

• Developing technologies to map and assess landslide susceptibility and risk. • Advancing our understanding of landslide processes and the geologic, topographic, hydrologic, and cultural factors that control slope failure. • Developing and demonstrating landslide prediction capabilities to avoid, prevent, or mitigate landslide damage. • Aiding the application of research results to improved planning, engineering design, and construction and to warning and emergency response plans.

These thresholds are now the basis for a public warning system like the one currently operating in the San Francisco Bay region.

Several larger, slow-moving landslides also were reactivated by the 1987–88 storm; these slides have been damaging several residential areas intermittently for more than 30 years. Scientists made detailed maps of landslide features and related damage in high-priority areas. These maps provided city and county officials with the first systematic portrayal of the underlying cause of

damage in apparently unrelated areas and supplied the basis for remedial efforts. Sophisticated analysis and computer modeling of this detailed mapping revealed that movement of the entire landslide mass is being driven by only a part of the landslide. This seemingly simple result has far-reaching implications. Stabilizing only the part of the landslide that is driving the whole mass is much more economical than stabilizing the entire landslide area. This modeling will provide the basis for innovative strategies to stabilize landslides in areas that have proven difficult to control by conventional methods. This cooperative project in Hawaii has combined the very best aspects of basic scientific research on landslide

Damage caused by a large, slow-moving landslide near Honolulu. This landslide, and others like it, disrupted streets, severed utilities, and damaged and destroyed many homes.

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power of earthquakes. The USGS Earthquake Hazards Reduction program (EHRP) is designed to help provide the Nation with the scientific and technical tools needed to significantly improve its social, economic, and environmental preparation for damaging earthquakes. The USGS effort seeks to achieve a clearer understanding of the nature of the earthquake process, define the specific earthquake hazard for various geographic regions in terms of how big the earthquakes could be, how often they might recur, and the likelihood of future significant earthquakes in each region, and predict the actual effects by defining specific characteristics of the shaking and how the Earth's surface will respond to

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the shaking (for example, landslides and soil liquefaction). Working cooperatively with other scientific agencies and many State and local officials to transfer the data, developed technologies, and risk assessments to those who need them is a critical program goal. Earthquakes are a unique class of hazards, unlike hurricanes, volcanoes, and floods, for which forecasts of timing and magnitude can be made hours to days in advance. Nonetheless, much can be done in advance to significantly reduce the risk from future earthquakes.

A Regional Approach to Earthquake Research

n the United States, earth scientists

have long recognized that the earthquake threat is not uniform across the Nation, as residents of Alaska and California can attest, and yet earthquakes are not exclusively a problem of the Pacific Coast States. The sequence of four earthquakes that struck the New Madrid, Mo., area in 1811–12 was probably the largest and most potentially damaging in the United States; a recurrence of an earthquake of similar magnitude would be felt from Denver to New York City and would damage buildings over thousands of square miles in eight States. The USGS

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and made about 100 awards on the basis of recommendations provided through a rigorous peer-review process. The regional coordinators have substantial input to setting the immediate and longterm needs to be addressed through this support. A few of the topics funded in FY 1993 include: • Providing support for a collaborative earthquake project with the State geological surveys of Washington, Oregon, and Alaska. • Deploying new state-of-the-art instrumentation on the Hayward fault in California to detect early signals of earthquake activity. • Verifying the occurrence of a major earthquake in the Upper Midwest Wabash Valley in the last 4,000 years. • Studying earthquake-wave attenuation in the Mississippi Embayment to improve predictions of future ground motion in urban areas including Memphis and St. Louis. • Discovering features in the Columbia River valley of Oregon that suggest major earthquakes occurred in the past 300 years.

Getting the Information Out

D. new technologies for transferring information is a vital part of the USGS earthquake program. For example, the fundamental earthquake data acquired at hundreds of monitoring stations are now routinely published in digital formats (such as CD-ROM), which scientists, engineers, planners, and local governments can acquire for a nominal fee. Each month, more Federal, State, local, and private agencies responsible for transportation, energy transmission, pipelines, and critical facilities access USGS telecommunication networks that provide information on recent or ongoing earthquakes. The USGS regional coordinators and individual USGS scientists work with broadbased regional earthquake mitigation groups such as the Central U.S. Earthquake Consortium (CUSEC), the Northeastern States Earthquake Consortium (NESEC), the Southern California Earthquake Center (SCEC), and Coordinating Organizations for Northern California Earthquake Research and Technology (CONCERT).

Geographic information systems (GIS) are now widely employed for communicating hazard and risk information on national, regional, State, and local scales. Use of GIS allows USGS products to be efficiently updated, enhanced, and disseminated either in hard copy, on computer disks, or by direct telecommunication links. For example, national maps showing the probabilities of expected levels of ground shaking for future earthquakes are the basis of seismic-design building codes across the country.

. . . national maps showing the probabilities

of expected levels

of ground shaking for future earthquakes

are the basis of seismic-design building codes

across the country.

Timely access to up-to-the-minute information on earthquakes anywhere in the Nation is critical to planning immediate and long-term responses. The USGS National Earthquake Information Center in Golden, Colo., disseminates much of this information. Analyses of the location, timing, and magnitude of an earthquake begin within seconds of the event, and distribution of the results by e-mail, fax, and telephone begins within minutes. In addition, the four regional earthquake offices, which have rapid access to regional seismograph networks, have a critical “onsite" role in the high-seismicity regions. The USGS Earthquake Hazards

Reduction program responds to user needs through public forums, technical results reported in scientific and engineering meetings and publications, policy group interactions, and vigorous collaboration with other Federal agencies such as the National Science Foundation, the Federal Emergency Management Agency, and the National Institute for Standards and Technology. Outreach activities in FY 1993 include:

© Collaboration with Humboldt State University in Arcata, Calif., to prepare and publish the full-color newspaper insert “On Shaky Ground–Living with Earthquakes on the North Coast.” • A workshop, in cooperation with the National Science Foundation, the National Academy of Sciences, and the Earthquake Engineering Research Institute, on the lessons learned from the Loma Prieta earthquake. • Two workshops, organized in conjunction with the Federal Emergency Management Agency, on the probabilities of damaging earthquakes in the Northeast, held in Boston, Mass., and on earthquake hazards in rural America, held in Boise, Idaho. • Collaboration with the Applied Technology Council on a major effort to develop new methods of transferring the latest results of USGS research to practicing engineers nationwide. • Completion of new national earthquake risk maps, which will be the basis of new Building Seismic Safety Commission building codes to be adopted nationwide. • Publication of USGS Professional Paper 1519 on the earthquake hazards and risk along the Wasatch Front, Utah.

Through these activities, the USGS Earthquake Hazards Reduction program continues to increase scientific understanding of how earthquakes happen and to disseminate that knowledge to decisionmakers, engineers, and the public. Understanding the earthquake process and carefully delineating the hazard posed by this process are major scientific challenges facing the Nation beyond the year 2000.

For more information about the Earthquake Hazards Reduction program, contact Randall Updike at:

Telephone (703) 648–6708 Internet rupdike(a

Randall G. Updike coordinates the USGS Earthquake Hazards Reduction program and has written extensively on earthquake processes

Understanding Volcano Hazards

ecent volcanic eruptions in the

United States and abroad have shown the potential impact of volcanic activity in terms of casualties (25,000 in Colombia in 1985 and 500 at Mount Pinatubo in 1991) and socioeconomic losses ($1 billion from Mount St. Helens in 1980 and $200 million from Redoubt

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