What is Earthquake?
Earthquake is the shaking of the surface of the earth, resulting from the sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can be violent enough to toss people around and destroy whole cities. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.
How can we measured Earthquake?
Earthquake are measured using measurements from seismographs. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe.
What is Seismograph?
Seismograph are instrument that measure motion of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources. History: In AD 132, Zhang Heng of China's Han dynasty invented the first seismoscope (by the definition above), which was called Houfeng Didong Yi (translated as, "instrument for measuring the seasonal winds and the movements of the Earth").
How a Seismograph Works?
Earthquake Zone Countries
1976 Tangshan Earthquake China: