Preventing Earthquake Disasters: The Grand Challenge in Earthquake Engineering A Research Agenda for the Network for Earthquake Engineering Simulation (NEES) (2003) / Chapter Skim
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2. Issues in Earthquake Engineering Research
2. Issues in Earthquake Engineering Research
Pages 26-62
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From page 26... ...
By disseminating and implementing the costeffective planning, design, construction, and response measures developed through NEES research, it will be possible to reduce injuries, loss of life, property damage, and the interruption of economic and social activity that have long been associated with strong earthquakes in densely developed regions. Earthquakes will continue to occur, but the disasters that they cause will be a thing of the past.
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From page 27... ...
Earth Sciences Englneerlng Social Sciences FIGURE 2.1 Nested linkages of activities and disciplines that NEES will bring to the resolution of earthquake engineering problems.
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From page 28... ...
The factors that influence strong ground motion during earthquakes are traditionally divided into source, path, and site effects. A fundamental challenge for earthquake engineering is predicting the level and variability of strong ground motion from future earthquakes.
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In addition to these constraints, there is ample evidence that slip in earthquakes is a strongly spatial variable (Mad and Beroza, 2002; Somerville et al., 1999; Andrews, 1980~. Because the excitation of ground motion by the earthquake source is dependent on the spatial variability of slip, efforts to predict strong ground motion from future earthquakes will probably involve source models that are described stochastically.
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From page 30... ...
During earthquakes, seismic waves become trapped and amplified by such basins, resulting in strong ground motion of long duration and strong spatial variation in amplitude, which can substantially increase the seismic forces on structures and lifelines (see, for example, Borcherdt, 1970; Phillips and Aki, 1986; and Trifunac et al., 1994~. Moreover, near the edges of such basins, complex interference effects can greatly amplify ground motion relative to what it would have been in the absence of edges and basin effects (Bard and Bouchon, 1985; Aki, 1988~.
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From page 31... ...
To predict strong ground motion, seismologists and engineers will have to characterize and account for anelastic wave effects in the earth's crust. Again, research efforts in this area will probably require partnerships between NEES and seismological research centers so that time-series data on an actual earthquake can be recorded as it occurs and made available for NEES experimental and testing purposes.
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From page 32... ...
Moreover, in this domain, wave propagation during strong ground motion is often nonlinear, with large-scale damage to geologic materials themselves, which in turn can lead to (for example) strong, amplitudedependent attenuation effects (Finn, 1988; Field et al., 1997~.
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From page 33... ...
Ground Motion Prediction The prediction of strong ground motion in future earthquakes is currently carried out primarily by applying attenuation laws, or parametric scaling relations (e.g., Abrahamson and Silva, 1997~. These relations link parameters describing the seismic source, such as the magnitude, and the
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From page 34... ...
All of these generation mechanisms involve a displacement of the ocean boundary, either at the seafloor, at the shoreline, or at the water surface. Since at the present time seismic data alone cannot define the important wave generation characteristics of these various tsunami sources, real-time deep water tsunami data are essential to forecasting tsunami impacts and providing critical boundary conditions for numerical models of their coastal effects.
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Between 1992 and 1994, the Nicaraguan tsunami, the Flores Island tsunami (Indonesia) , and the Hokkaido tsunami (lapan)
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For example, the Alaska earthquake and tsunami of 1964 and the Chilean earthquake and tsunami in 1960 caused damage and loss of life along the Pacific west coast from Alaska to California as well as in Hawaii. Approximately 120 people lost their lives in the Alaska tsunami of 1964, and the estimated damage from that event along the West Coast and in Hawaii was about $600 million in current dollars.
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investigated the potential tsunami hazard to southern California using such a numerical simulation. Wave generation due to tectonic uplift or downthrow of the ocean bottom and submarine landslides near the coast was modeled.
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From page 38... ...
Once inundation zones are defined, emergency preparedness authorities can determine evacuation routes and routes for search and rescue, while planners can develop priorities for measures such as the relocation of critical and high-occupancy facilities as well as for providing information to coastal residents. (For real-time warnings, NOAA currently uses real-time tsunami data from the deep ocean and from coastal sensors as well as real-time seismic data in concert with numerical models to forecast tsunami coastal impacts.)
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From page 39... ...
Some of the damage on the island of Okushiri (Japan) caused by the 1993 Hokkaido tsunami can be attributed to a perhaps unexpected aspect of tsunamiinduced forces namely, the inundating wave toppled home fuel storage tanks mounted on supports above the ground, contributing to massive fires that caused significant damage in addition to that caused directly by wave inundation.
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From page 40... ...
The challenge for tsunami hazard mitigation is to provide a real-time description of tsunamis at the coastline for warning, evacuation, engineering, and mitigation strategies. This can best be accomplished by means of a complete numerical simulation of tsunami generation, propagation, and coastal effects that is experimentally verified and, if necessary, combined with selected real-time tsunami data.
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From page 41... ...
Several urban centers in seismically active regions rely on reclaimed land areas to support industrial facilities, airports, and port and shipping facilities. For instance, in the United States, a significant percentage of the major port and shipping facilities on the West Coast are on reclaimed land, and all San Francisco Bay Area airports are on alluvial or reclaimed areas.
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Reproduced courtesy of the National Information Service for Earthquake Engineering, University of California, Berkeley.
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From page 43... ...
during the San Fernando earthquake of 1971 offered an excellent case history of the seismic performance of embankment dams constructed on and of liquefiable materials. In fact, the most common problem leading to the instability of embankment dams in a seismic environment is the presence of liquefiable soils in the dams themselves or in the foundations on which they rest (Marcuson et al., 1996~.
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From page 44... ...
In contrast to the increasing number of successful case histories for buildings, bridges, ports, or oil storage tank sites on improved ground, there have been few documented case histories for the earthquake performance of an embankment dam with an improved section or an improved foundation. One notable exception is the Lake Chaplain South Dam, improved with stone columns in the toe prior to the 2001 Nisqually, Washington, earthquake (Hausler and Koelling, 2003~.
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From page 45... ...
Ground shaking in these areas, underlain by soft soils, was greater than the shaking in nearby surrounding areas founded on shallower, stiffer soils. The significant increase in damage potential due to soft soils calls for a better understanding of how local soil conditions modify seismic shaking and how these conditions can be identified, designed for, and/or modified.
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From page 46... ...
Priority issues in building-related earthquake engineering research include prediction of the seismic capacity and performance of existing and new buildings, evaluation of nonstructural systems, performance of soil-foundation-structure interaction systems, and determination of the performance of innovative materials and structures. Prediction of the Seismic Capacity and Performance of Existing and New Buildings Perhaps the greatest overall seismic risk in the United States is the severe earthquake damage (including collapse)
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From page 47... ...
buildings, concrete-framed buildings, concrete wall "tilt-up" industrial buildings, precast concrete buildings, certain types of steel-framed buildings, and many pre-1975 structures, including wood-framed houses, apartments, and commercial buildings. Figure 2.6 shows structural damage to an unreinforced masonry building during the Northridge earthquake.
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From page 48... ...
To understand adequately and to better model these interactions, full-scale models of buildings need to be develFIGURE 2.7 Nonstructural building damage at the Olive View Medical Center experienced in the 1971 San Fernando, California, earthquake. Reproduced courtesy of the National Information Service for Earthquake Engineering, University of California, Berkeley.
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From page 49... ...
Smart materials can be used in sensors or actuators. Examples of smart sensing materials include optical fiber, shape memory alloys, and microelectromechanical systems (MEMS)
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For example, in 1987, an action plan was developed to address seismic hazards to lifelines (FEMA, 1987~. In 1998, FEMA and the American Society of Civil Engineers entered into a cooperative agreement to establish the American Lifelines Alliance to facilitate the "creation, adoption and implementation of design and retrofit guidelines and other national consensus documents that, when implemented by lifeline owners and operators, will systematically improve the performance of utility and transportation systems to acceptable levels in natural hazard events, including earthquakes." Many utilities in highly seismic areas have implemented programs to replace system components that have been judged vulnerable to earthquake hazards such as ground shaking or soil failure.
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From page 51... ...
In summary, the principal earthquake hazards for highways, railroads, and mass transit systems are ground shaking, seismic wave propagation, and ground failure. Research is needed on several aspects of the response of bridge spans to seismic motions namely, relative displacement of girder ends as a result of differential ground motion, the use of
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52 PREVENTING EARTHQUAKE DISASTERS FIGURE 2.8 Failure of a span of the Nishinomiya Bridge during the 1995 Kobe, Japan, earthquake. Reproduced courtesy of the National Information Service for Earthquake Engineering, University of California, Berkeley.
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From page 53... ...
Port facilities are located throughout the United States in seismically active areas and are typically susceptible to structural damage resulting from foundation failure, such as liquefaction-induced ground settlement or lateral spread and tsunami run-up and impact. The Kobe, Japan, earthquake of 1995 damaged numerous waterfront facilities, mainly through liquefaction of loosely placed fill materials.
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From page 54... ...
The principal earthquake hazards include ground failure due to liquefaction or landslides, settlement, ground-shaking effects on aboveground facilities and equipment, and the surface rupture of faults. The principal research needs unique to gas and liquid-fuel systems relate to soil restraint and/or loading on buried pipelines; the determination of compressive, postbuckling strain limit states; and the study of strain localization associated with pipe wrinkling under high compressive loads.
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From page 55... ...
Water and sewage systems consist of pipelines, pump stations, compressor stations, storage tanks and reservoirs, control systems, and water purification systems. The principal earthquake hazards include ground failure due to liquefaction or landslides, settlement, ground-shaking effects on aboveground facilities and equipment, and surface rupture of faults.
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In addition, certain industrial facilities might transport, handle, or produce hazardous materials that could be released as a result of earthquake damage. As with buildings, the principal earthquake hazard affecting industrial systems is ground shaking.
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Risk assessment requires knowledge of the following types of problems: · The likelihood of earthquake events, their size and location, ground shaking and ground failures throughout their influence area, and the likelihood of their causing tsunamis or seiches. · Physical damage, with its direct consequences in terms of death, injury, loss of operational functionality, and destruction of property.
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From page 58... ...
There is a strong case to be made for a holistic technical-social-economic approach to implementing earthquake mitigation measures. Petak notes that mitigation technology has advanced considerably over the years but deployment has not kept pace, even in earthquake-prone California (Petak, 2003~.
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From page 59... ...
The technical basis comes from integration of all the geologic, structural, and sociological data to plan for a realistic potential disaster. Knowledge from NEES and other NEHRP programs can define the earthquake hazard and simulate the vulnerability of community infrastructures.
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1988. Local site effects on strong ground motion.
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Paper 10.15 in Fourth International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, March 26-31. Heaton, T.H.
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From page 62... ...
1999. Characterizing crustal earthquake slip models for the prediction of strong ground motion.
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