Living on an Active Earth Perspectives on Earthquake Science (2003) / Chapter Skim
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1. The Challenge of Earthquake Science
1. The Challenge of Earthquake Science
Pages 1-18
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However, in just the last decade, new instrumental networks for recording seismic waves and geodetic motions have mushroomed across the planet, and new methods for deciphering the geological record of earthquakes have been applied to active faults in many tectonic environments. High-performance computing is now furnishing the means to process massive streams of observations and, through numerical simulation, to quantify many as1
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These perspectives are summarized below. 1.1 SEISMIC SAFETY AND PERFORMANCE Earthquakes are hazards primarily because strong ground shaking destroys things that people have constructed buildings, transportation lifelines, and communication systems (Figure 1.1~.
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This event killed at least 5500 people, injured more than 26,000, and was responsible for approximately 5200 billion in direct economic losses. SOURCE: Pan-Asia Newspaper Alliance.
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in in o C' . _ 10 1 FIGURE 1.2 Direct economic losses, given in inflation-adjusted 1994 dollars on a logarithmic scale, from some major earthquakes in the United States and Japan.
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The total AEL estimated for the entire United States is about 54.4 billion. SOURCE: FEMA, HAZUS 99 Estimated Annualized Earthquake Losses for the United States, FEMA Report 366, Washington, D.C., 33 pp., February 2001.
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Earthquake risk reduction must thus rely on lowering vulnerability through earthquake-resilient design of new structures and retrofitting or rehabilitating inadequate older structures to improve their seismic safety. Provisions for earthquake design are now an integral part of building codes in most seismically active parts of the United States, although some states with moderate earthquake risk do not have state seismic codes (see Chapter 2~.
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and megacities (more than 8 million inhabitants, solid stars) in the year 2000, relative to the major earthquake belts (shaded regions)
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1.2 SEISMIC INFORMATION FOR EMERGENCY RESPONSE Science and technology can do nothing to prevent or control large earthquakes, and as yet no known method can reliably predict when, where, and how big future tremors will be. However, once an earthquake occurs, advanced seismic information systems can transmit signals from dense networks of seismometers to central processing facilities and, in a fraction of a minute, pinpoint the initial fault rupture (hypocenter)
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in the Los Angeles area. In regions with advanced seismic information systems, maps such as this can be broadcast to emergency management agencies within a few minutes, providing critical information for organizing emergency response.
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These waves travel relatively slowly (500 to 700 kilometers per hour) , so post-event predictions of tsunami arrival times and amplitudes can be used to warn coastal communities soon enough to allow for preparation and evacuation.
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Correspondingly, many disciplines seismology, tectonic geodesy, earthquake geology, rock mechanics, complex systems theory, and information technology are producing the conceptual innovations needed for the practical issues of seismic hazard analysis, risk reduction, and rapid emergency response. Fundamental work on elastic wave scattering in fractal media has been applied to prediction of the strong ground motions that damage buildings.
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Earthquakes in nearly all tectonic environments share similar scaling laws (e.g., frequency-magnitude statistics, aftershock decay rates, stress drops) , which suggests that some of the most basic aspects of earthquake behavior are universal and not sensitive to the details of deformation processes.
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The content and methods for teaching earthquake science in primary and secondary schools remain pressing subjects that should engage more scientists involved in basic research. National science education standards recommend that Earth science be taught at all grade levels (18~.
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Earth science needs a healthy program of earthquake research to attract the best candidates. 1.5 PREDICTIVE UNDERSTANDING The main goal of earthquake research is to learn how to predict the behavior of earthquake systems.
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Chapter 3 gives the current view of seismic hazards on a national and global scale and shows how an improved characterization of these hazards can reduce earthquake losses by lessening risk and speeding response. Chapter 4 describes the observational activities and research methods in four major disciplines seismology, tectonic geodesy, earthquake geology, and rock mechanics and discusses the advanced technologies being employed to gather new information on the detailed workings of active fault systems.
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3. Federal Emergency Management Agency, HAZUS~99 Estimated Annualized Earthquake Losses for the United States, FEMA Report 366, Washington, D.C., 33 pp., February 2001.
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Geological Survey National Earthquake Information Center, and international sources. If the location and magnitude of an earthquake meet the known criteria for generating a tsunami, a warning is issued to emergency managers and the general public.
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Interferometric Synthetic Aperture Radar (InSAR) Initiative, for using satellite-based InSAR to map surface deformations, especially the deformation fields associated with active faults and volcanoes ( |
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