![]() ![]() 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. ![]() For instance, thick layers of soft soil (such 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. The intensity of local ground-shaking depends on several factors besides the magnitude of the earthquake, one of the most important being soil conditions. With an isoseismal map of the observed intensities (see illustration) an earthquake's magnitude can be estimated from both the maximum intensity observed (usually but not always near the epicenter), and from the extent of the area where the earthquake was felt. Intensity refers to the strength or force of shaking at a given location, and can be related to the peak ground velocity. It is "approximately related to the released seismic energy." Magnitude is an estimate of the relative "size" or strength of an earthquake, and thus its potential for causing ground-shaking. 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. The Earth's crust is stressed by tectonic forces. The irregular distribution of shaking arises from variations of geology and/or ground conditions. 0.0000028 of the most massive earthquake recorded, Chile '60 □Īlso, by typing "1" into any field in the "Energy release equivalent" section, you can check what's the equivalent magnitude for a chosen energy release event – for example, one Nagasaki bomb released the energy of a 6.Isoseismal map for the 1968 Illinois earthquake.The released energy is 31622776601684 J, and the equivalent of such energy is:.And that's it! The earthquake magnitude calculator shows not only the energy but also some energy equivalents for the given magnitude:.You may be wondering – how "big" is that? Type the value into the earthquake magnitude box. You may have heard that a 5.8 earthquake hit Alaska recently.Use it as the earthquakes' magnitude calculator to compare two earthquakes' magnitudes. Thanks to this earthquake calculator, you can:Ĭheck the approximate energy release of an earthquake in energy release equivalents (such as tons of TNT, atomic bomb energies, and volcanic eruptions). Most masonry, frame structures, and their foundations destroyed. Some walls collapse.Ĭonsiderable damage to specially built structures, buildings shifted off foundations. Some walls may fall.Ĭonsiderable damage to ordinary buildings, severe damage to poorly built structures. ![]() Considerable damage to poorly built structures. Slight to moderate damage in well-built, ordinary structures. Some heavy furniture moved, some plaster falls. Pendulum clocks may stop.įelt by nearly everyone. Dishes, windows, doors disturbed.įelt by almost everyone, wakes many. May not be recognized as an earthquake.įelt by many indoors, few outdoors. Noticeable indoors, especially on upper floors. Recorded by seismographs.įelt by a few people, especially on the upper floors. ![]()
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