Seismic magnitude scales the amount of slip, the area of the surface ruptured or slipped, and a factor for the resistance or friction encountered. These factors can be estimated for an existing fault to determine the magnitude of past earthquakes, or what might be anticipated for the future. An earthquake's seismic moment can be estimated in various ways, which are the bases of the M, M, M, M, M, M, and M scales, all subtypes of the generic M scale. See for details. Seismic moment is considered the most objective measure of an earthquake's "size" in regard of total energy. However, it is
Seismic source are efficient seismic sources because of their reduced costs, ease of transport in difficult terrains, and lack of regular maintenance compared to other sources,the use of explosives is becoming restricted in certain areas, causing decline and increasing popularity for alternative seismic sources. For instance, hexanitrostilbene was the main explosive fill in the "thumper" mortar round canisters used as part of the Apollo Lunar Active Seismic Experiments. Generally, the explosive charges are placed between below ground, in a hole that is drilled with dedicated drilling equipment for this purpose. This type of seismic drilling is often referred to as "Shot Hole