SCEC INSTANeT News
	Earthquake Science and Engineering in California: Ongoing Programs and New Initiatives for the 21st Century

By Dr. Thomas Henyey, SCEC Executive Director Devastating earthquakes in California in 1989 (Loma Prieta) and 1994 (Northridge) together with the 1992 Landers and 1999 Hector Mines events remind us that our State faces a serious earthquake risk that only increases with each passing day as our population continues to expand. Recent estimates of aggregate damages due to plausible earthquakes on any one of a dozen active fault segments in the State are in the tens of billions of dollars. Much to our benefit, California has a long history of addressing the earthquake risk, and it is imperative that those efforts continue into the 21st century with the next generation of tools. Seismic monitoring networks to locate the sources of earthquakes were first established in northern and southern California in the early part of last century following the devastating 1906 San Francisco earthquake. However, only modest improvements were made over the ensuing 70 years. With passage of the National Earthquake Hazards Reduction Act in 1977, major network upgrades took place, and a new era of earthquake science and engineering research began ­ research aimed at understanding where and why devastating earthquakes occur, what sort of ground shaking could be expected, and what could be done to the built environment to reduce the overall risk. The National Earthquake Hazards Reduction Act tasked the U.S. Geological Survey with coordinating the earthquake monitoring and research activities. Most California and U.S. seismic networks continue to operate with 1970's technology. In the 1990's, in order to coordinate research activities within California by the academic community, integrate research findings, and disseminate research results, two organizations, each with specific yet complementary research missions, were established by the National Science Foundation. The first (in 1991) was the Southern California Earthquake Center (SCEC), an NSF Science and Technology Center focused on the earthquake hazard including characterizing active faults, determining earthquake probabilities, and forecasting strong ground motions from future events. The second (in 1997) was the Pacific Earthquake Engineering Research Center (PEER) with a mission to reduce, through performance-based structural engineering, earthquake risks to life, property, and the economy. SCEC's output is PEER's input; i.e., improving structural performance depends upon an improved knowledge of ground motions. In parallel with these two research centers, action was taken in the 1990's to improve the seismic and engineering infrastructure in California. Following the 1994 Northridge Earthquake, the California Institute of Technology, California Division of Mines and Geology, and U.S. Geological Survey joined forces to propose TriNet -­ an upgrade of the southern California seismic monitoring networks that included new state-of-the-art seismometers and an increase in the number of strong motion detectors for engineering application. This action was taken to accelerate our understanding of earthquake sources and the ground motions they produce throughout southern California. An application for funding TriNet, coordinated by the California Governor's Office of Emergency Services, was sent to FEMA, and subsequently approved. More recently, the northern California seismic network operated by UC Berkeley has been appended to TriNet. Full implementation of TriNet will depend on the extent of cost-sharing by the State and other non-federal organizations. A second improvement in infrastructure occurred with the approval by NSF and Congress (NSF MRE Account) of the Network for Earthquake Engineering Simulation (NEES) to create new, and upgrade existing, shake tables, and use Information Technology to mitigate the effects of earthquakes by making a complete set of testing and modeling facilities widely available to the engineering community. NEES, in turn, will be networked with earthquake science centers and seismological data bases that will provide ground motion information needed in static and dynamic simulations. As with TriNet, full implementation of NEES has not yet occurred. With the beginning of the new millennium, two new infrastructure or facilities initiatives are now pending before Congress that will make use of advanced technologies and allow earthquake scientists to peer into every nook and cranny of California's and the nation's "earthquake machine", and dismember it piece by piece. One newly proposed facility is the Advanced National Seismic System (ANSS) submitted by the U.S. Geological Survey, and the other is EarthScope, proposed by the National Science Foundation through the MRE Account. ANSS will organize, modernize, and standardize seismic monitoring in the United States with a permanent national array of linked high-fidelity seismic detectors, recording systems, and data distribution centers with universal access. ANSS will provide: 1) alerts of imminent strong earthquake shaking, 2) rapid assessments of the distribution and severity of earthquake shaking, 3) warnings of volcanic eruptions and possible tsunami, 4) information for correctly characterizing earthquake hazards, and 5) critically needed data on the response of buildings and other structures during earthquakes. The second new facility, EarthScope, will have a different but complementary mission. It will make use of a combination of moveable seismic arrays, fault zone drilling, and satellite technology (Global Positioning System, GPS, and Synthetic Aperture Radar, SAR) to probe seismogenic structures, including fault and volcanic systems, with an unprecedented degree of resolution. Its mission will be to define the structure of the crust and how it changes over time. The moveable seismic arrays can be positioned directly over active faults to explore, in detail, their subsurface geometries using CAT-Scan techniques, or around active volcanoes to investigate the intricacies of their plumbing systems. The fault zone drilling will cut through these faults at depth to unmask the physical conditions under which earthquakes nucleate, while GPS and SAR will provide synoptic maps of how the crust is deforming in real time as plate tectonic forces move us toward the next major earthquake or volcanic eruption. Also, mapping the overall structure of the crust will allow us to accurately simulate, using high-performance computers, the probable ground motions from future plausible earthquakes for input to performance-based engineering design. As with ANSS, linked regional and national data centers using state-of-the-art Information Technology will provide for universal access to the data by the scientific and engineering communities, as well as by the general public. In short, ANSS and EarthScope are important steps in our efforts to locate and characterize active faults, improve earthquake and volcano forecasting, map the patterns of crustal deformation and strain build-up in western U.S., and predict future earthquake ground motions with the detail needed by engineers to design cost-effective earthquake resistant structures. They will not only greatly increase the firepower with which we have to study earthquakes and volcanoes, but also bring new technologies to bear on important societal problems.

Phone 213/740-5843 Fax 213/740-0011 e-mail: SCECinfo@usc.edu