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Politics : Bush-The Mastermind behind 9/11? -- Ignore unavailable to you. Want to Upgrade?

To: GUSTAVE JAEGER who wrote (9665)	1/11/2005 10:27:00 AM
From: sea_urchin	Read Replies (1) \| Respond to of 20039

Gus > The Richter scale is an open ended logarithmic scale. No earthquake could ever be off such a scale Theoretically, yes, but there are practical problems. encyclopedia.thefreedictionary.com >>Richter arbitrarily chose a magnitude 0 event to be an earthquake that would show a maximum combined horizontal displacement of 1 micrometre on a seismogram recorded using a Wood-Anderson torsion seismometer located 100 km from the earthquake epicenter. This choice was made to prevent negative magnitudes from being assigned. However, the Richter scale has no upper or lower limit. Sensitive modern seismographs now routinely record quakes with negative magnitudes. Because of the limitations of the Wood-Anderson torsion seismometer used to develop the scale, the original ML cannot be calculated for events larger than about 6.8. Many investigators have proposed extensions to the local magnitude scale, the most popular being the surface wave In physics, a surface wave is a wave that is guided along the interface between two different media for a mechanical wave, or by a refractive index gradient for an electromagnetic wave. The major problem with Richter magnitude is that it is not easily related to physical characteristics of the earthquake source. Furthermore, there is a saturation effect at near 8.3-8.5, owing to the scaling law of earthquake spectra, that causes traditional magnitude methods (such as MS) to yield the same magnitude estimate for events that are clearly of different size. Intensity is sensitive to a host of local site conditions and is not an absolute measurements of earthquake size. Events with magnitudes of about 4.5 or greater are strong enough to be recorded by seismographs all over the world. <<