Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Early Earthquake Detection Instruments

Skip navigational links
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: 08:31 - 09:35 (01:04)
Source: Annenberg/CPB Resources - Earth Revealed - 9. Earthquakes
Keywords: "James Sadd", earthquake, seismograph, China, "initial ground motion", vibration, "duplex pendulum", "San Francisco Earthquake", strength, duration, epicenter

Our transcription: In the second century the Chinese built a device that could detect the initial ground motion during an earthquake.
It consisted of eight metal balls ranged around the circumference of a large sphere.
If the Earth shook hard enough, a small pendulum inside the sphere swung back and forth knocking one of the balls off its stand.
This indicated the direction that the earthquake vibrations came from.
At the turn of the century a more advanced device was designed, one to make a permanent record of ground motion during an earthquake.
This instrument, called a duplex pendulum seismograph recorded the shaking of the ground as a continuous squiggle on a piece of paper.
It was this device that recorded the ground motion of the 1906 San Francisco Earthquake.
The invention of a device that could accurately measure the strength of an earthquake was a significant scientific achievement.
These modern seismographs operate on the same general principles as the early pendulum instruments, but they are much more sensitive.
Not only do they record vibrations, but they can be used to measure earthquake strength and duration, and also to determine the location of the earthquake almost immediately.

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 logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: InfoBank staff
Page Last Modified: Thu Oct 31 04:26:03 PDT 2013  (chd)