What is the magnitude of an earthquake estimated from measurements of the amplitude of surface waves called?

The magnitude of an earthquake estimated from measurements of the amplitude of surface waves is referred to as Surface-Wave Magnitude, commonly denoted as M_s. This specific method focuses on the surface waves that travel along the Earth's crust, which typically cause the most damage during an earthquake.

Surface waves have larger amplitudes compared to other types of seismic waves, and their measurement is particularly useful for determining the magnitude of larger, distant earthquakes. M_s is calculated using the maximum amplitude of surface waves recorded by seismographs and adjusts for the distance from the seismic source to the measuring station.

In contrast, options like Body-Wave Magnitude focus on other seismic wave types, such as primary (P) and secondary (S) waves, while Local Magnitude is often used for smaller, nearby earthquakes and utilizes different criteria and calculations. Moment Magnitude, on the other hand, provides a more comprehensive measure based on fault area, slip, and the rigidity of the materials involved, which can give broader applications but does not specifically rely on surface wave amplitude. Thus, the correct answer accurately captures the method of estimating earthquake magnitude using surface wave data specifically.