Moment magnitude scale formula8/16/2023 This enables them to calculate the distance the earthquake is from the seismograph.įirst slide details. Then they compare the difference in arrival times of the S waves. To locate the epicenter of an earthquake, we need to look at seismograms from three different recording stations.Įxperts compare the difference in arrival times of the P waves at the different stations. It is more directly related to the energy of an earthquake than other scales, and does not saturatethat is, it does not underestimate magnitudes as other scales do in certain conditions. The magnitude 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. The resulting pattern, or seismogram, reveals to experts: Moment magnitude (M w) is considered the authoritative magnitude scale for ranking earthquakes by size. Sal explains the basics of the Richter scale (Moment magnitude scale) and uses this to compare the magnitude of 4 famous earthquakes. Modern versions are all computerized and instantly record activity at the seismic station. Older versions are anchored to the ground and have a pen attached to them, so when the Earth moves during a quake the device moves and the pen makes zigzag tracings on paper. The waves are measured on sensitive instruments called seismographs. Seismologists compare the arrival times of P waves and S waves at seismic stations to determine a quake's location. You can see from the equation that momentum is directly proportional to the object’s mass ( m) and velocity ( v ). Surface waves follow at the slowest speed, causing intensive damage as they move along the Earth's surface. Secondary waves (S waves) move slower than P waves and vibrate at right angles to the direction of wave travel. Primary waves (P waves) travel at the fastest speeds and spread through the crust from the hypocenter, alternately squeezing and stretching the rock as they travel through it. When the quake begins, seismic waves travel rapidly outward in all directions. It is calculated using a formula that includes the rigidity of the. The epicenter is the point on the surface directly above the hypocenter. The Moment Magnitude Scale measures the amount of energy released by an earthquake event. The hypocenter (or focus), the place where the movement first occurred on the fault, can be hundreds of kilometers below the Earth's surface or just beneath it. Sorry, your browser doesn't support embedded videos.
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