Doing Business. Emergency Management. How are earthquakes recorded? How are earthquakes measured? How is the magnitude of an earthquake determined? There are many different ways to measure different aspects of an earthquake: Magnitude is the most common measure of an earthquake's size. It is a measure of the size of the earthquake source and is the same number no matter where you are or what the shaking feels like.
The Richter scale is an outdated method for measuring magnitude that is no longer used by the USGS for large, teleseismic earthquakes.
The Richter scale measures the largest wiggle amplitude on the recording, but other magnitude scales measure different parts of the earthquake. The USGS currently reports earthquake magnitudes using the Moment Magnitude scale , though many other magnitudes are calculated for research and comparison purposes.
Intensity is a measure of the shaking and damage caused by the earthquake; this value changes from location to location. What is the difference between earthquake magnitude and earthquake intensity? What is the Modified Mercalli Intensity Scale? Moment magnitude, Richter scale - what are the different magnitude scales, and why are there so many? How do you determine the magnitude for an earthquake that occurred prior to the creation of the magnitude scale?
How do seismologists locate an earthquake? What was the duration of the earthquake? Why don't you report the duration of each earthquake? How does the duration affect the magnitude? How can an earthquake have a negative magnitude? What does it mean that the earthquake occurred at a depth of 0 km? What is the geoid, and what does it have to do with earthquake depth? Seismometers, seismographs, seismograms - what's the difference?
How do they work? How can I make my own seismometer? Recording earthquakes is not a problem although it can still be a challenge for seismologists. Seismograph: Seismographs or also called seismometers are very important tools in the field of measuring earthquakes.
These tools are used in seismic stations throughout the world. A seismograph draws lines in what is called a seismogram to record and measure earthquakes. The seismographs are used for recording earthquakes and measuring because it draws lines which indicate ground motion. A seismograph is used for recording because the seismogram can be stored and studied by seismologists. This great tool is used for detecting the movement of the crust.
GPS is mostly in satellites. A better measure of the size of an earthquake is the amount of energy released by the earthquake, which is related to the Richter Scale by the following equation:. Tectonic earthquakes can range in size from magnitudes less than zero, resulting from fault slippage of a few centimetres, to the largest events magnitude greater than 9 , where fault displacements are on the order of many metres.
Earthquake size is determined not only by amount of displacement but also area of the ruptured fault plane. Hence the larger the rupture area, the larger is the earthquake. A magnitude 7 earthquake ruptures a fault area of about km2 or about 50 km long and 20 km wide. Also depth is an important factor influencing earthquake severity. We know that earthquakes can originate at various depths within the Earth's solid core. The deeper the earthquake, the more powerful it is, but it is also far less likely to reach the surface.
That's why shallow earthquakes are more common and more dangerous, because the shallower an earthquake, the more damage to surface structures it can cause. There is no limit to the possible magnitude of an earthquake but historically just over magnitude 9 is the record. The seismoscope is a simple instrument that measures the time that an earthquake takes place. The seismograph records the motion of the ground during an earthquake. Seismograms record seismic waves.
Over the past century, scientists have developed several ways of measuring earthquake intensity.
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