Earthquake Glossary - G or g
G or g
g is the acceleration of gravity 9.8 (m/s2) or the strength of the gravitational field (N/kg) (which it turns out is equivalent). G is the proportionality constant 6.67x10-11 (N-m2/kg2) in Newton's law of gravity. On the other hand, the force of gravity, or F = mg, at the surface of the earth, or F = GMm/r2 at a distance r from the center of the earth (where r is greater than the radius of the earth). When there is an earthquake, the forces caused by the shaking can be measured as a percentage of gravity, or percent g.