Seismic magnitude scales by tectonic forces. When this stress becomes great enough to rupture the crust, or to overcome the friction that prevents one block of crust from slipping past another, energy is released, some of it in the form of various kinds of seismic waves that cause ground-shaking, or quaking. "Magnitude" is an estimate of the relative "size" or strength of an "earthquake", and thus its potential for causing ground-shaking. It is "approximately related to the released seismic energy." "Intensity" refers to the strength or force of "shaking" at a given location, and can be related to the peak ground velocity. With
Seismic Experiment for Interior Structure has large marsquakes, they may allow the deep interior to be determined. As the vibrations pass through the planet they are affected by the properties of the materials and its configuration. For example, the effect of tidal forces on Mars by Phobos, which should be about 10 mm, would be noticeably affected by a liquid Mars core. Even without any marsquake, it should be possible after about six months of observation to use this method to increase or decrease the likelihood Mars has a liquid core. Seismic Experiment for Interior Structure The Seismic Experiment for Interior Structure (SEIS) is a