Characterizing Earthquake Hazards in the U.S.: Earth Science and Societal Challenges

By

Ivan G. Wong

URS Corporation, Oakland, CA

In the past two decades, our understanding of earthquake source processes, the distribution and seismogenic potential of active faults in the U.S., and seismic wave propagation has improved significantly. Much of this increase in knowledge has been due to three scientific advancements: 1) the development and applications of the relatively new science of paleoseismology, 2) significant improvements in seismographic instrumentation accompanied by increased instrumental density in California and expansion into poorly instrumented regions of the U.S., and 3) the development of numerical techniques to model earthquake sources and ground motions. The information resulting from these approaches has led to significant advances in our understanding of earthquake hazards throughout the U.S. For example, the Pacific Northwest, once thought to be a generally aseismic region not more than 20 years ago (except for the Puget Sound), has now been characterized as one of the most hazardous regions in the U.S. because of the potential for magnitude (M) 9 earthquakes occurring in the Cascadia subduction zone. Despite important scientific accomplishments, significant challenges lie ahead particularly in terms of characterizing the distribution of coseismic slip on faults, earthquake recurrence, ground motion attenuation, and geologic site response effects.

The breakthroughs in earthquake sciences have been impressive, but equivalent success in convincing society of earthquake hazards has not occurred. Although from a probabilistic perspective, earthquakes outside of California are rare events in the timeframe of individual lives, the impact of a large earthquake occurring near an urban center could be catastrophic because of the lack of preparation. For the U.S. to be successful in reducing inevitable earthquake losses, earth scientists need to be more engaged in educating the general public, the engineering community, and government decision-makers of the hazards and risks posed by earthquakes.

AAPG Search and Discovery Article #90004©2002 AAPG Rocky Mountain Section, Laramie, Wyoming