Seismic intensity scales as fill) can amplify seismic waves, often at a considerable distance from the source, while sedimentary basins will often resonate, increasing the duration of shaking. This is why, in the 1989 Loma Prieta earthquake, the Marina district of San Francisco was one of the most damaged areas, though it was nearly 100 km from the epicenter. Geological structures were also significant, such as where seismic waves passing under the south end of San Francisco Bay reflected off the base of the Earth's crust towards San Francisco and Oakland. A similar effect channeled seismic waves between the other major faults in
Passive seismic have been also applied in another planets. For instance, during Apollo missions, the Passive Seismic Experiment sensors were deployed that detected lunar "moonquakes" and provided information about the internal structure of the Moon. Passive seismic is much less expensive than well drilling. It is also cheaper and more environmentally friendly than active seismic, which requires a strong source of the seismic waves (like an underground explosion) to predict the structure. In some cases it may be the only method for which land access is granted by the land owner. Despite the method having been successfully applied in many parts of