- As defined, an earthquake magnitude scale has no lower or upper limit. Sensitive seismographs can record earthquakes with magnitudes of negative value and have recorded magnitudes up to about 9.0. (The 1906 San Francisco earthquake, for example, had a Richter magnitude of 8.25.)
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It depends on other variables, such as the distance from the earthquake, what type of soil you are on, etc. That being said, damage does not usually occur until the earthquake magnitude reaches somewhere above 4 or 5. Learn more: Earthquake Magnitude, Energy Release, and Shaking Intensity
Nov 30, 2016 · Great earthquakes, such as the 1964 Good Friday earthquake in Alaska, have magnitudes of 8.0 or higher. On the average, one earthquake of such size occurs somewhere in the world each year. Although the Richter Scale has no upper limit, the largest known shocks have had magnitudes in the 8.8 to 8.9 range.
Earthquake size, as measured by the Richter Scale is a well known, but not well understood, concept. The idea of a logarithmic earthquake magnitude scale was first developed by Charles Richter in the 1930's for measuring the size of earthquakes occurring in southern California using relatively high-frequency data from nearby seismograph stations...
- More About Magnitudes - The 3 Approaches
- Magnitude and Energy
- Magnitude vs. Intensity
- One Final Word - A Plea For Understanding
A familiar analogy to help understand earthquake size metrics is to think about a light bulb. One measure of the strength of a light bulb is how much energy it uses. A 100-watt bulb is brighter than a 50-watt bulb, but not nearly as bright as a 250-watt bulb. The wattage of a bulb tells you about the strength of the light source. In the same way, an earthquake's magnitudeis an objective measurement of the energy radiated by an earthquake. 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. 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. An earthquake causing motion at that distance 10 times large...
Earthquake intensitymeasures how strongly the earthquake impacts a specific location. In the light bulb analogy, it is the brightness with which you perceive the light at a place in a room. 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. Well, you can make a map of earthquake impacts using the Modified Mercalli Intensity Scale (MMI), which derived from an earlier ten-degree Rossi-Forel scale, later revised by Italian vulcanologist Giuseppe Mercalli in 1884 and 1906 to quantify (somewhat) the earthquake's effects. Further refinements for more modern construction were published in 1931 by the American seismologists Harry Wood and Frank Neumann. Measurements of intensity using the Modified Mercalli scale, are composed of 12 increasing levels that r...
If you've had some time to think a bit about the Earthquake/Light bulb analogy you probably have come up with some questions, like: But some bulbs are blue and some white and some yellow, what gives with that? And, fluorescent fixtures put out really different quality light than incandescents, and are brighter for the same wattage, eh? And, what about a flash bulb from my camera which is incredibly bright...but just for a fraction of second? And, if my room is filled with steam or smoke, is the intensity still the same? These are all good points; it turns out that similarly for earthquakes the complexities and variability of earthquake rupture processes and of seismic waves as they travel through Earth (and evolving seismometer design and sensitivities) there are different methods for measuring the magnitude of an earthquake. These may return a slightly different number when used to estimate the energy released in an earthquake. In overview, there are three approaches to using seism...
Below is a representation, from the Geological Society of America, of earthquake magnitudes and the equivalent energy release. (For the life of us, we don't know why the geologists used pounds of explosive as a proxy for energy instead of a real physical unit of energy, such as Joules! But the figure makes the point, anyway.) Notice the relationship is not linear? The change in the amount of energy released from one magnitude to the next is greater as the earthquake magnitude increases. For example, the difference in amount of energy released from a magnitude 5 to a magnitude 10 is not double, it is 30 million times as much! Need some further practice relating Earthquake Magnitude to Energy? No problem, the USGS calculates the difference between a 5.8 and 8.7 earthquake and has a calculatorwhere you can input your own numbers to see how much bigger an earthquake can get with different magnitudes.
The chart below claims to compare Richter Scale magnitudes with intensities in a very generalized way--as if a "Richter magnitude" was somehow measuring the same thing as a "Mercalli intensity". Now that you know the basics of earthquake Magnitudes and earthquake Intensities, you know that this chart makes no sense. If you see it or a similar representation, you can be assured the provider of the information is unencumbered by knowledge of the basics.
Now that you know how many different approaches there are to measuring an earthquake, and how it depends on the traces that you use, and instrument types that you have available and how far they are from the earthquake, and how many there are.... Perhaps you'll understand why our magnitude estimates change with time immediately after an earthquake as we try to be both as fast and as accurate as possible. And why different organizations will post somewhat different magnitudes for the same earthquake. A rule of thumb, perhaps, is that in the early minutes (or tens of minutes) after an earthquake up to a half a magnitude unit of difference between estimates will generally be shrugged off by seismologists as reasonable scatter. But differences larger than that usually mean that there was a fairly serious problem...like the entirely wrong technique was used, or critical data were omitted.
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Jul 22, 2020 · An earthquake has one magnitude unit. The magnitude does not depend on the location where measurement is made. Since 1970, the Moment Magnitude Scale has been used because it supports earthquake detection all over the Earth.
Apr 09, 2021 · Magnitude scale of landslide events exponential and logarithmic functions intensity and scales power and frequency of earthquakes solved on the richter scale. On the richter scale magnitude m of an earthquake is given by 2 3loge eo where e brainly regional relationships among earthquake magnitude scales solved the richter scale provides a ...
An earthquake has one value for magnitude (energy released) and usually several values for intensity. The greatest intensity is usually recorded close to where the earthquake takes place (epicenter) and decreases with distance from the epicenter.
May 04, 2021 · At magnitude levels of 4.0 to 6.0 most homes would not collapse but may suffer low to significant damage. A magnitude of 6.7 can produce enormous stress on a building’s structural components, including foundations, beams, columns, walls and floors, as well as the connectors that hold the components together.