Correct Option
The correct option is (b).
Explanation
Earthquake measurement involves recording seismic waves to determine the event's location, magnitude, and intensity. Instruments record the ground motion, while specific scales are used to quantify the energy released (magnitude) and the severity of shaking at a specific location (intensity).
Statement-wise Analysis
- Statement 1 is Incorrect: An earthquake is measured with an instrument called a Seismograph (or Seismometer), which records seismic waves. A barometer is used to measure atmospheric pressure.
- Statement 2 is Correct: The magnitude of an earthquake is measured on the Richter scale. This scale quantifies the energy released during the earthquake. It is a logarithmic scale, where an increase of one unit represents a tenfold increase in wave amplitude and approximately 32 times more energy.
- Statement 3 is Incorrect: An earthquake of magnitude 5.0 is classified as moderate. It may cause slight damage to buildings and other structures. Earthquakes are generally classified as major when they reach a magnitude of 7.0 to 7.9 on the Richter scale.
Key Takeaway
Seismographs are the instruments used to record earthquakes. The Richter scale measures magnitude (energy released), whereas the Mercalli scale measures intensity (visible damage). A magnitude of 7.0 or higher is required for an earthquake to be termed "major."