Moment magnitude scale The scale was unable to characterize these "great earthquakes" accurately. The difficulties with use of in characterizing the quake resulted from the size of these earthquakes. Great quakes produced 20 s waves such that was comparable to normal quakes, but also produced very long period waves (more than 200 s) which carried large amounts of energy. As a result, use of the modified Richter scale methodology to estimate earthquake energy was deficient at high energies. The concept of seismic moment was introduced in 1966 by Keiiti Aki, a professor of geophysics at the Massachusetts Institute of Technology. He employed elastic
Magnitude (astronomy) been classified as "stars of the first magnitude". Magnitudes can also be calculated for objects far brighter than stars (such as the Sun and Moon), and for objects too faint for the human eye to see (such as Pluto). Often, only apparent magnitude is mentioned since it can be measured directly. Absolute magnitude can be calculated from apparent magnitude and distance from: This is known as the distance modulus, where is the distance to the star measured in parsecs, is the apparent magnitude, and is the absolute magnitude. If the line of sight between the object and observer is affected