Counts of occurrence per depth in 福島県会津

Counts of occurrence per depth in 福島県会津（Aizu area of Fukushima Pref.）is shown as below graph, 

Most earthquakes were occurred in 1km-20km (95%). Both M6.2 of 30km in 1943 and M5.5 of 10km in 1994 were occurred around the end of the long silent terms. On the other hand, both of M5.7 of 10km in 2010 and M6.3 of 1km in 2013 seem to be related with M9.0 Great East Japan Earthquake even though the epicenter far from this area. In 2025, there is the rapid increase of 1km curve. It is concerned that there might be larger one in the near future.

1km (red)…The count is the 2nd. There was the rapid increase of 1km in 1924. But, the maximum magnitude between 1919-1930 was only M4.3. Most of them are unknown details with no data of magnitude. There was the longer silent term between 1939-1942. It seems to be the sign of M6.2 of 30km in 1943. Similarly, M5.5 of 10km in 1994 was occurred around the term end of the longest silent term between 1987-1995. By the M5.5, 10km curve was accelerated, and 1km curve was also done in late 2010s. After overtaken by 10km curve, there was M9.0 Great East Japan Earthquake. Even though the epicenter was far from this area, many earthquakes were induced. M6.3 of 1km was one of them in 2013. The M6.3 was the greatest one of all depths in this area. In 2025, there is the rapid increase. As the maximum of them is only M5.2, it is concerned that there might be larger one in the near future. If the same rapid increase is occurred in 1km, the risk should become higher.

10km (yellow)…The count is the 1st. 10km curve overtook 20km curve in 1942.  M6.2 of 10km was occurred 9 months later in 1943. the rapid increase of 10km in 1924. As mentioned above, 1km's longer silent term between 1939-1942 also seems to be related. The steep slope of 10km continued after that. M5.5 of 10km was occurred in 1994 as mentioned above, too. Furthermore, M5.7 of 10km was occurred in 2010, and it made 10km curve jump up and overtake 1km curve. The rapid increase seems to be one of signs of the M9.0. The M5.7 of 10km is the largest one.

20km(orange)…The count is the 3rd. After overtaken by 10km curve, 20km curve become far from 10km curve gradually. The silent term also became longer gradually. The last occurrence was in 2000. The longest silent term is extended still now. The largest magnitude is M4.9 in 1987. 

others… Remaining counts except 1km-20km are only 5%.