What is a seismograph ?

An earthquake measures 3 on Richter scale : Would it be recorded by a seismograph ?

Earthquake at two place I and II were measured by a seismograph and recorded as 2 and 4. What is the magnitude of tremors and its destructive energy at I and II?

Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?

During earthquake, both longifudinal and transverse waves are produced having speeds 4.0km//s and 8.0km//s respectively. If the first transverse wave reahes the seismograph 8 miniutes after the arrival of first longitudinal wave, then find the distance of the position, where the earthquake occured.

Earthquakes generate sound waves inside Earth. Unlike a gas, Earth can experience both transverse (S) and longitudinal (P) sound waves. Typically, the speed of S waves is about 4.5 km/s, and that of P waves 8.0 km/s. A seismograph records P and S waves from an earthquake. The first P waves arrive 3.5 min before the first S waves. If the waves travel in a straight line, how far away did the earthquake occur?