Measurment of Earthquakes

Suggest any two scales that are used to measure the magnitude of earthquakes.

Answer: Richter Scale and Moment MagnitudeScale.

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How are earthquakes measured?

• A network of seismographs is used to record earthquakes with each individual seismograph recording and measuring the movement of the ground in its location.
• A seismograph is securely mounted onto the surface of the earth so that when the earth shakes, the entire unit shakes with the exception of the mass on the spring, which remains in its place because of inertia.
• During shaking, the recording device on this mass records the relative motion between itself and the rest of the instrument, thus recording the ground motion.
• These mechanisms work by measuring electronic changes produced by the motion of the ground with respect to the mass.

The scales of measurement for magnitude:

• Richter Scale: Devised in 1935 by Charles Francis Richter, the Richter Scale (denoted as ML) is a logarithmic scale, where each step represents a tenfold increase in magnitude.
• Moment Magnitude Scale: provides a more accurate estimate of magnitude, especially as one goes higher up the logarithmic scale.

The scales of measurement for intensity:

• The Modified Mercalli Scale and the Rossi-Forel scale, measure the amount of shaking at a particular location.
• The Modified Mercalli Scale ranks earthquake intensity on a scale of I. (not felt) to XII. (extreme).