For more information

Web site:

http://www.usgs.gov/

The USGS homepage provides lists of current earthquake information; current seismic activity; maps; earthquake parameters on global, national, and regional scales; general information on earthquakes and earthquake research; and seismic data in near real-time from national and world-wide stations.

Research Raises Earthquake Awareness in Pacific Northwest

The Puget Sound region lies in a complicated and potentially dangerous tectonic setting. Not only can moderate earthquakes of about magnitude 7 occur in the shallow part of the Earth's crust under Puget Sound, but also evidence has been discovered in the last few years that large earthquakes of magnitude 8 or greater can strike the region.

These large earthquakes occur at greater depths in regions called subduction zones, where the oceanic crust is forced beneath the continental crust. Evidence for these large earthquakes has been collected over the past 10 years from studies of large tracts of submerged land near the coast. Field evidence for a large, subduction zone earthquake circa A.D. 1700 has recently been augmented by tree-ring studies and by historical tsunami records from Japan.

The impact of this research has been substantial. The Uniform Building Code contains nationwide standards for structure design. Before 1994 the code placed the Puget Sound area in a zone having the second highest hazard level defined in the code, and most of Oregon and Washington was placed in a zone having the next lower hazard level. A later addition to the Uniform Building Code extends the higher level hazard zone to include western parts of Washington and Oregon that are near the potential sources of these great earthquakes. This extension of the higher hazard level is based on USGS research.

USGS work in this region has brought attention to the earthquake hazard problems of the area. From 1988 to 1995, the public and private sectors invested more than $130 million

to strengthen bridges, dams, lifelines (electrical, gas, and water lines), and buildings against earthquakes in the Pacific Northwest. These improvements in resistance to earthquake shaking reduce the region's vulnerability to loss of life and property from future earthquakes.

Private and public institutions have formed the Cascadia Region Earthquake Working Group (CREW) to address the earthquake hazards issues. Participants in CREW include representatives from the aircraft, computer software, and transportation industries and representatives from the banking and insurance sectors. The USGS provides CREW with scientific information and advice on the nature and severity of earthquakes.