I know earthquake is measured by Rictor scale but how do they know where to keep the scale in advance. Before, a quake coming up, how do they know that this place is likely to have quake in certain time and they keep one over there to measure? Is it random that they keep?
In: Physics
What you’re referring to is broadly called the seismographic network. We have sensors kinda…everywhere. All over the place, globally.
It’s also worth noting that given the precision of modern instruments you don’t need to measure *at the quake*. We have instruments sensitive enough to pick up the effects of an earthquake hundreds, if not thousands of miles away.
And we generally don’t determine the magnitude of an earthquake based on the reading of *one* seismograph. We base it on readings of multiple ones. And based on when each individual seismograph registers the quake, how strong it was at that point and time and based on a whole lot of math and triangulation, we can determine where and when it was.
We don’t *need* seismograph in Los Angeles to know when an earth quake hit Los Angeles, or when, or how strong it is. If we have one in Hawaii and one in Idaho and one in Rio, and we know when each one went off, we can compare the strength and time of its effect in each of those three areas and calculate backwards. If we know how fast the seismic wave is moving, and we know it’s strength at 3 separate locations, we can triangulate backwards.
They have a bunch of measuring stations all over the world that are constantly measuring 24/7. They also aren’t just measuring noticeable earthquakes, or measuring where the quake happened. They measure every little seizmic wave that happens everywhere, and when a quake happens in one place, they’ll get data of it from all over the world
1. The Richter Scale is not an actual physical measuring device. It’s just a system for ranking how strong Earthquakes are. It’s like the Scoville Heat Scale for ranking spicy foods or the “Celsius” and “Fahrenheit” scales for temperature. The Richter Scale is a set of numbers used to communicate earthquake strength. It does not **do** the measuring; there is no device called a “Richter Scale”.
2. The device that measures earthquake shaking is called a seismograph. There’s a [network of them all around the world](https://www.researchgate.net/publication/226172456/figure/fig11/AS:668281950199825@1536342241593/Map-of-station-locations-of-the-Global-Seismographic-Network-that-monitors-worldwide.ppm), all running and recording nonstop 24/7. The great thing about that is you don’t actually need one at the site of an earthquake! We know how fast the shaking travels, and how much it decreases with distance. So when there’s an Earthquake, you can just compare measurements from a few of these stations. Since you know when it hit each station and how strong it was when it got there, there’s math to work out exactly where the shaking came from and how strong it was when it left. This process is called *triangulation* if you want to search more details.
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