2.4 FAQs

1. What is the Definition of an Earthquake?

An earthquake is the sudden, sometimes violent movement of the earth's surface from the release of energy in the earth's crust.

2. What Causes Most Earthquakes?

The crust of the earth when it is subject to tectonic forces, bends slightly. But, because the crust is rigid, when the stress or pressure exceeds the strength of the rocks, the crust breaks and snaps into a new position. Vibrations called seismic waves are generated and travel both through the earth and along its surface. These seismic waves cause the movement we call earthquakes.

3. Where Are Earthquakes Likely to Occur?

Within areas of the crust are fractures, known as faults, along which two crustal blocks have slipped or moved against each other. One block may move up while the other moves down, or one may move horizontally in one direction and the other in the opposite direction. Geologists and seismologists (scientists who study earthquakes and the processes that create them) have found that earthquakes occur repeatedly at faults, which are zones of weakness in the earth's crust.

4. Where Do Most Earthquakes Occur in the World?

The surface of the earth is divided like a jigsaw puzzle into giant pieces called tectonic or crustal plates. These giant pieces move slowly over partially melted rock known as the mantle. As they move, they slide along each other, move into each other, move away from each other, or one slips under another. On these active plate boundaries about 95% of all the world's earthquakes occur. California, Alaska, Japan, South America, and the Philippines are all on plate boundaries. Only 5% are in areas of the plates far away from the boundaries. These are called mid-plate or intra-plate earthquakes and are, as yet, poorly understood.

5. What Was the Greatest Number of People Killed in One Earthquake?

An earthquake in China in 1556 killed approximately 830,000 people.

6. Can buildings be designed to withstand earthquakes?

Yes! Engineers can, and are, designing earthquake-resistant structures

2.5 Related References and Building Codes

  • Dowrick, D. J., "Earthquake Resistant Design", John Wiley Second Edition 1989.
  • Key, D. E., "Earthquake Design Practice for Buildings", Thomas Telford 1988.
  • Naeim, F., "Seismic Design Handbook", Van Nostrand Rheinhold 1989.
  • "Earthquake Spectra", Earthquake Engineering Research Institute, 6431 Fairmount Avenue, Suite 7, El Cerrito, California CA94530, USA.
  • "Earthquake Engineering & Structural Dynamics", John Wiley.
  • "Earthquake Engineering", Robert L. Wiegel Prentice Hall 1970.
  • Gere, J. M. and Shah, H. C., Terra Non Firma - Understanding and preparing for earthquakes, Stanford Alumni Association, Stanford, USA, 1984.
  • 'Design of Earthquake - Resistant Buildings', Minoru Wakabayashi, McGraw-Hill, Paris, 1986.
  • National Information Service for Earthquake Engineering (NISEE), University of California, Berkeley Web Site http://nisee.berkeley.edu/
  • USGS Web Site, http://earthquake.usgs.gov/
  • The Multidisciplinary Center for Earthquake Engineering Research (MCEER) Web Site http://mceer.buffalo.edu/
  • Earthquake Engineering Research Instute Web Site, http://www.eeri.org/
  • AISC Web Site www.aisc.org
  • Eurocode 1, Eurocode 3, Eurocode 8, Commission of the European Communities
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