seismic instruments. Other intensity scales measure felt intensity, based on eyewitness reports, felt shaking, and observed damage. There is correlation between these scales, but not always absolute agreement since experiences and damage can be affected by many other factors, including the quality of earthquake engineering. Generally speaking, 0.001 g (0.01 m/s) – perceptible by people 0.02 g (0.2 m/s) – people lose their balance 0.50 g (5 m/s) – very high; well-designed buildings can survive if the duration is short. Correlation with the Mercalli scale The United States Geological Survey developed an Instrumental Intensity scale, which maps peak ground acceleration and peak ground velocity on an intensity scale similar to the felt Mercalli scale. These values are used to create shake maps by seismologists around the world. Other intensity scales In the 7-class Japan Meteorological Agency seismic intensity scale, the highest intensity, Shindo 7, covers accelerations greater than 4 m/s (0.41 g). PGA hazard risks worldwide In India, areas with expected PGA values higher than 0.36 g are classed as "Zone 5", or "Very High Damage Risk Zone". Notable earthquakes See also Earthquake simulation Japan Meteorological Agency seismic intensity scale Spectral acceleration References Bibliography Seismology Earthquake engineering Acceleration