Strong ground motion

Strong ground motion

"Peak ground velocity" redirects here."

Seismologists usually define strong ground motion as the strong earthquake shaking that occurs close to (less than about 50 km from) a causative fault. The strength of the shaking involved in strong ground motion usually overwhelms a seismometer, forcing the use of accelerographs (or strong ground motion accelerometers) for recording.

As seismic instruments (and accelerometers in particular) become more common, it becomes necessary to correlate expected damage with instrument-readings. The old Modified Mercalli intensity scale (MM), a relic of the pre-instrument days, remains useful in the sense that each intensity-level provides an observable difference in seismic damage.

After many years of trying every possible manipulation of accelerometer-time histories, it turns out that the extremely simple peak ground velocity (PGV) provides the best correlation with damage. [ http://pasadena.wr.usgs.gov/shake/pubs/shake/node7.html and http://www.ingentaconnect.com/content/klu/nhaz/2004/00000032/00000003/05144506] PGV merely expresses the peak of the first integration of the acceleration record. Accepted formulae now link PGV with MM Intensity. Note that the effect of soft soils gets built into the process, since one can expect that these foundation conditions will amplify the PGV significantly.

ShakeMap [http://earthquake.usgs.gov/shakemap/ and http://www.shakemap.carleton.ca/] systems tie all of this together into a useful product. Some systems use seismometers and accelerometers to produce a near-instantaneous map of expected MM Intensities after a significant earthquake. As well, people can send in their observations of earthquake effects to help fill in the maps, which can help disaster-relief teams and other agencies.

The science of strong ground motion also deals with the variations of fault rupture, both in total displacement, energy released, rupture velocity, etc.

See also

* A [http://www.alyeska-pipe.com/Inthenews/techpapers/2-TAPS%20Fault%20Crossing%20Denali%20EQ.pdf paper] describing how the Alaska Pipeline dealt with the toughest engineering challenge of all: straddling an active fault

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • motion picture — motion picture, adj. 1. a sequence of consecutive pictures of objects photographed in motion by a specially designed camera (motion picture camera) and thrown on a screen by a projector (motion picture projector) in such rapid succession as to… …   Universalium

  • Peak ground acceleration — (PGA) is a measure of earthquake acceleration on the ground and an important input parameter for earthquake engineering, also known as the design basis earthquake ground motion (DBEGM)[1] Unlike the Richter and moment magnitude scales, it is not… …   Wikipedia

  • Ground blizzard — refers to a weather condition where loose snow or ice on the ground is lifted and blown by strong winds. The primary difference between a ground blizzard as opposed to a regular blizzard is that in a ground blizzard no precipitation is produced… …   Wikipedia

  • Ground glass joint — Ground glass joints are used in laboratories to quickly and easily fit leak tight apparatus together from commonly available parts. For example, a round bottom flask, Liebig condenser, and oil bubbler with ground glass joints may be rapidly… …   Wikipedia

  • motion picture, history of the — Introduction       history of the medium from the 19th century to the present. Early years, 1830–1910 Origins       The illusion of motion pictures is based on the optical phenomena known as persistence of vision and the phi phenomenon. The first …   Universalium

  • Motion Picture & Television Country House and Hospital — The Motion Picture Television Country House and Hospital is a retirement community, with individual cottages, and a fully licensed, acute care hospital, located at 23388 Mulholland Drive in Woodland Hills, California. It is a service of the… …   Wikipedia

  • New Ground (Star Trek: The Next Generation) — New Ground Star Trek: The Next Generation episode Worf, at Alexander s arrival on the Enterprise. Episo …   Wikipedia

  • Perpetual motion — For other uses, see Perpetual motion (disambiguation). Robert Fludd s 1618 water screw perpetual motion machine from a 1660 wood engraving. This device is widely credited as the first recorded attempt to describe such a device in order to produce …   Wikipedia

  • Airs above the ground — For the Mary Stewart novel, see Airs Above the Ground (novel). The levade …   Wikipedia

  • Oblique motion — Oblique Ob*lique , a. [F., fr. L. obliquus; ob (see {Ob }) + liquis oblique; cf. licinus bent upward, Gr. le chrios slanting.] [Written also {oblike}.] [1913 Webster] 1. Not erect or perpendicular; neither parallel to, nor at right angles from,… …   The Collaborative International Dictionary of English

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”