What is a dual?
I can give you an example easier than I can explain it. Magnetism is the right hand of Electricity and Electricity is the right hand of Magnetism. They are right and left of each other, like twins. The Wikipedia lists other duals in physics as:
- Dual resonance model
- Duality (electricity and magnetism)
- Englert–Greenberger duality relation
- Holographic duality
- Kramers–Wannier duality
- List of dualities (physics)
- Mirror symmetry
- Montonen–Olive duality
So you can see no shortage of the concepts.
Here is another one:
Volcanic eruptions are the “Dual” of earthquakes. And what appears to be their joint cause or precursors are Tropical storms. It appears that Tropical storms too have their duals. And I am not talking about when they become Extra Tropical storms. (Hurricanes once they leave the vicinity of the subtropics become Cold Core storms commonly known as Extra Tropical storms.)
Tropical storms have their counterpoint in the northern waters of the Pacific and Atlantic and corresponding mirror images in the Southern Ocean.
Without being able to forecast which ocean the next tropical storms are going to occur in but with a reasonably good idea of the likely dates, we can use the duals of tropical storms to forecast hurricanes and typhoons because we are extremely good at forecasting storms in Northern waters and because the computer models used by the Australian Bureau of Meteorology to forecast events in the southern Oceans is a particularly good one.
Some storms end with a unique series of small consecutive quakes and some “end”(?) with a volcanic eruption. The reason for thinking of these phenomena as duals is that volcanoes erupting is a likelihood when there is such a degree of stillness, vorticity or instability in the system despite the demise of a certain part of it (one or two storms) and yet another storm continues with a lot of energy and may be joined by others springing up.
In the case of all storms going into decline, the result will be earthquakes either one large one or two of half that one’s power.
In the case of a storm ending despite conditions favourable to storms continuing, the rotational forces go underground. (It may be that the storm ended because it ran out of road. Once it hits a shore it has to obey the rules for cyclosis.)
More study of these phenomena are required