Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Types of Ground Vibrations

Skip navigational links
Loading
Dictionaries: Our Mapping Systems   The USGS and Science Education   USGS Fact Sheets   Topics   Keywords   Data Dictionary   Metadata Dictionary   Computer Terminology   Digital Formats  
InfoBank Terms: Activity ID   activity overview   crew   digital data   formal metadata   lines   metadata   NGDC   port stops   project/theme   region   ship   stations   time   virtual globe   year  
Data Types: bathymetry   biological   geochemical   gravity   ground penetrating radar   imaging   LIDAR   logs   magnetics   metering equipment   navigation   samples   seismic   total station   definitions disclaimer  
Data Formats: ARC coverage   E00   FGDC metadata   gridded/image   imaging   material   scattered/swath   Shapefile   vector/polygon  
Comment: 13:44 - 14:21 (00:37)
Source: Annenberg/CPB Resources - Earth Revealed - 9. Earthquakes
Keywords: earthquake, "wave period", "natural period", vibration, "primary wave", "secondary wave", "surface wave", "ground motion", epicenter

Our transcription: There are many different types of ground vibrations.
The rapid vibrations of the primary and secondary waves and the slower rolling motion of what are called surface waves.
Near the epicenter where all these vibrations are concentrated at the same location ground motion is similar to the complex sea surface in an ocean storm with waves of all sizes mixed together, but the longer waves travel faster and may not die out for hundreds of kilometers.
The amount of time it takes two successive wave crests to pass a stationary point is called the wave's "period."
For longer seismic waves, this period may be several seconds.
Other materials including buildings have a period associated with them. In a strong gust of wind a skyscraper will flex and bend.
The time it takes for the skyscraper to oscillate back and forth once is called its natural period.
When the period of a seismic wave matches the natural period of a building, the seismic energy is simply added to the oscillation of the building, wave after wave.
As a result, the swaying of the building increases dramatically.
Other buildings of different heights will not be similarly affected because their natural periods are different.

Geology School Keywords
Skip footer navigational links

Coastal and Marine Science Centers:  Pacific   St. Petersburg   Woods Hole  
InfoBank   Coastal and Marine Geology Program   Geologic Information   Ask-A-Geologist   USGS Disclaimer  


Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://walrus.wr.usgs.gov/infobank/programs/html/school/moviepage/08.01.16.html
Page Contact Information: InfoBank staff
Page Last Modified: Thu Oct 31 04:26:04 PDT 2013  (chd)