One big earthquake induces many other earthquakes around it.Sometimes, it induces bigger ones.The dynamics seems to be similar with domino's one.Big domino piece can push down the same or smaller pieces.Sometimes, high speed pieces can push down even bigger one.If not pushed down,tilted piece can stock the kinetic energy as potential energy.It seems to be similar with earthquake dynamics.
In my understanding, stress comes from deep Earth crust area.In deeper area, there is higher pressure.So, every movement of Earth crust should be limited.In fact,most of earthquakes came from deeper area in Japan.Based on the database of Japan Meteorological Agency(JMA), the numbers of earthquakes per the depth are as the graph as below,
(note)The counts are done by me.The earthquakes of 0km includes "Details Unknown" with unknown depth just as my judgment.
The number of class of 0km is more than 100 thousands,and it's almost half of the total number.On the other hand, the numbers of deeper than 100km is only less than 2%. This result may reflect the fact that deeper earthquakes are primordial than the shallower ones.
The 2 figures shows the results selected with 100km deeper from JMA database directly as below,
Period : 1/1/1919-1/6/2025
Magnitude : M6.0-M9.9
Depth : 100km-999km
Period : 1/1/1919-1/6/2025
Magnitude : M0.0-M4.0
Depth : 100km-999km
Even though the number of earthquakes with M0.0-M4.0 (condition 2) are 2 times more than with M6.0-M9.9 (condition 1), the distribution on the map are less than.As I described above, the every movement are limited, less magnitude should mean near the origins of cracking. The curve of epicenters shows the plate edge.In M6.0-M9.9 (condition 1), most of epicenters also stay near the plate edge curves.
As you know, continental plate movement is the main cause of earthquakes near the Pacific-rim, and Pacific Ring of Fire exists along it.
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