fundamentals of earthquake engineering

1.1 Introduction
This chapter provides a basic understanding of earthquakes, by first discussing the causes of earthquakes,
then defining commonly used terms, explaining how earthquakes are measured, discussing the distribution
of seismicity, and, finally, explaining how seismicity can be characterized.
Earthquakes are broad-banded vibratory ground motions, resulting from a number of causes
including tectonic ground motions, volcanism, landslides, rockbursts, and man-made explosions. Of
these, naturally occurring tectonic-related earthquakes are the largest and most important. These are
caused by the fracture and sliding of rock along faults within the Earth’s crust. A fault is a zone of the
earth’s crust within which the two sides have moved — faults may be hundreds of miles long, from one
to over one hundred miles deep, and are sometimes not readily apparent on the ground surface.
Earthquakes initiate a number of phenomena or agents, termed seismic hazards, which can cause significant
damage to the built environment — these include fault rupture, vibratory ground motion
(i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure
(e.g., liquefaction), fire, or hazardous materials release. In a particular earthquake event, any particular
hazard can dominate, and historically each has caused major damage and great loss of life in particular
earthquakes.
For most earthquakes, shaking is the dominant and most widespread agent of damage. Shaking near
the actual earthquake rupture lasts only during the time when the fault ruptures, a process that takes
1.1 Introduction ................................................... 1-1
1.2 Causes of Earthquakes and Faulting ..................... 1-2
1.3 Measurement of Earthquakes 1-5
Magnitude
Intensity
Time History
Elastic Response
Spectra
Inelastic Response Spectra
1.4 Distribution of Seismicity .................................. 1-20
1.5 Strong Motion Attenuation and Duration ............. 1-21
1.6 Characterization of Seismicity ............................. 1-26
Glossary................................................................. 1-28
References .............................................................. 1-30
Further


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