Can you read a fine-print book by the lamp? Pick up a needle? Perform delicate surgery? Depends on the wattage of the bulb, and how far you are from it, right? If you mapped out the brightness in terms of what you could accomplish at the light level in a room, you'd have an intensity map. In the light bulb analogy, it is the brightness with which you perceive the light at a place in a room. This Live Science animation will help you visualize the exponential magnitude scale in terms of energy released.Įarthquake intensity measures how strongly the earthquake impacts a specific location. An earthquake that releases about 33 times less energy and causes motion 10 times smaller than an M1 is an M0-and magnitudes can even go negative. When referring to the power or energy released in an earthquake this 32 multiplier is used. To achieve this ten fold increase in ground motion requires about 32 to 33 times the energy. An earthquake causing motion at that distance 10 times larger than an M2 is an M3, and so on. It is easier to choose a particular earthquake recorded at a particular distance as a "standard" earthquake and call it a magnitude 1. An earthquake that causes ground motion at a seismic station (when corrected for distance) 10 times larger than the reference earthquake is M2. However, earthquake magnitude has no physical units, nor a meaningful 0. This is because we can't easily measure the energy the way we can with an electric circuit, so seismologists commonly use a relative measure. In the same way, an earthquake's magnitude is an objective measurement of the energy radiated by an earthquake. The wattage of a bulb tells you about the strength of the light source. A 100-watt bulb is brighter than a 50-watt bulb, but not nearly as bright as a 250-watt bulb. One measure of the strength of a light bulb is how much energy it uses. ![]() And when news announcers mention the "Richter Scale" seismologists the world over begin gnashing their teeth.Ī familiar analogy to help understand earthquake size metrics is to think about a light bulb. There often seems to be no end of confusion, misunderstanding, and over-interpretation of what are really pretty crude metrics. This scale is more useful in a sense that it provides some insight into the fault plane geometry of the earthquake based on parameter $M_0$.Perhaps no seismic subject is as irksome to seismologists as discussions of earthquake size. The magnitude( $M_0$) is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of the area that slipped. Where $M_0$ is the seismic moment in N⋅m ( $10^7$ dyne⋅cm). The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). The problem with most scales is that they become saturated after a certain magnitude.ģ scales can be named which fall in this category An earthquake measured to 9.0 is one million times stronger than an earthquake at 5.0. A difference in magnitude of 2.0 is equivalent to a factor of 1000. Some of the confusion might come from that the Richter scale is logarithmic. There are few other scales, Body wave magnitude, surface wave magnitude, but to my knowledge they also stay under 10. Related to the Richter's scale is the Moment magnitude scale, it's an updated better way to measure, but it usually produce similar values as the old Richter's scale and the two scales are often confused in media. Magnitude is also measured in different scales. Medvedev–Sponheuer–Karnik scale is used in some Asian and European countries, Russia, India, Israel etc. XII on the Medvedev–Sponheuer–Karnik scale is Very catastrophic and IX in Destructive. China seismic intensity scale (CSIS), Medvedev–Sponheuer–Karnik scale and European macroseismic scale can reach values above ten, but not 13-14. ![]() Modified Mercalli Intensity scale is a way to rate the intensity of an earthquake, but the scale ends at XII (Damage total), not at 13-14 (XIII-XIV), as mentioned. Naturally an earthquake with high magnitude would also generate high intensity, but the intensity depends on distance from the hypocenter and the local geological conditions. Intensity is determined from effects on buildings, landscape and people. Magnitude is the energy released of the earthquake. Magnitude and intensity are related but measure very different properties of the event. Earthquakes are measured for intensity and magnitude.
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