A Richter scale nomograph helps one estimate earthquake magnitudes from seismograph readings.
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This activity presents a seismograph reading from an earthquake and a chart which can be used to estimate the magnitude of the earthquake on the Richter Scale. The chart is called a nomograph and is used in the following way:
The user examines the seismograph to determine how much time has elapsed between the arrival of the first P-waves and the arrival of the first S-waves. This time, in seconds, is plotted on the left chart axis yielding an estimate of the distance between the siesmograph station and the earthquake epicenter.
The user then measures the amplitude of the strongest seismograph signal in millimeters and plots this on the right chart axis. This represents how strong the earthquake waves are when they are observed at the siesmograph station.
Lastly, a line is drawn between the two plotted points. This line intersects with the central axis. This intersection point yields the estimated magnitude of the earthquake on the Richter scale.
