Counts of occurrence per depth in 埼玉県北部

Counts of occurrence per depth in 埼玉県北部 (North Saitama Pref.)  is shown as below graph,

Though the count of 1km is the 1st, the occurrence has stopped since 1950. Such long silent term may suggest the charge of earthquake energy. Both 40km/50km curves had such long silent terms for more than 60 years, the energy might be stocked still around these depths. So, the huge earthquake like M6.9 in 1931 seems to be occurred be in the distant future maybe.  

 1km (red)…The count is the 1st.  But, the new occurrence of 1km has stopped since 1950. There was the rapid increase by the aftershocks of M7.9 Great Kanto Earthquake in 1923. There was the next rapid increase in 1931 by M6.9 of 1km. The M6.9 is the greatest one of all depths. Before the M7.9 in 1923, there was the 4th longest silent (at that time, the 1st) term between 1920-1922.  Similarly, there was the 5th longest term (at that time, the 2nd) between 1928-1930 before the M6.9 of 1km in 1923. As the 1st longest silent term is extending more than 75 years, there might be more than M6.9 in this area in someday. But, it may be in the distant future.

20km (orange)…The count is the 2nd. As same as 1km curve, there was the rapid increase by the M6.9 of 1km in 1923. But, the rapid increase was interrupted when the count of 20km became the same as count =65. The silent term between count 65/66 was the longest one at that time (the rank has become out of top ten). After it, there has been no remarkable increase. The longest silent term was between 1972-1981. The silent term has become shorter gradually after it. The largest one of 20km is M5.5 in 1931.

10km (yellow)…The count is the 3rd. As same as 1km/10km curves, there was the rapid increase by the aftershocks of the M6.9 of 1km in 1923. 10km curve is following behind 20km curve. The largest one of 10km is M4.7 in 1931. 

60km (blue)…The count is the 4th. As there had been no remarkable rapid increase, 60km curve increased with gentle slope. But, the steady increase of 60km curve has made the difference between 10km curve and 60km curve narrow especially during the last 20 years. The largest one of 60km is M5.5 in 2015. 

70km (purple)…The count is the 5th. 70km curve is following behind 60km curve. But, 70km curve has separated from 60km by resent 60km increase. The largest one of 70km is M6.1 in 1968.

50km (light blue)…The count is the 6th. 50km curve had overcome 70km curve until 1985. But, during the longest silent term of 50km between 1974-2001, 50km curve was overtaken both 60km/70km curves. The largest one of 90km is M5.5 in 1928. 

90km (brown)…The count is the 7th. 90km was following behind 70km. As there was the rapid increase in 1996, the difference between 90km/70km has become less recently. The largest one of 90km is M4.8 in 1996.  

100km(gray) …The count is the 8th. Both 100km/90km curves had almost overlapped between 1933-1996. 100km was remained by the rapid increase of 90km in 1996. The largest one of 100km is M4.6 in 2013.  

30km (yellow green)…The count is the 9th. There was the rapid increase of 30km as same as 1km/20km curves. But, the increase has stopped since 1974. The largest one of 30km is M5.5 in 1931.  

120km(-)…The count is the 10th. As the count=1 was M5.7 in 1920, only the first one of 120km is plotted. The M5.7 of 120km is the largest one.

40km (green)…The count is the 11th as same as 130km(omitted). There was the longest silent term between 1946-2011. The length is almost same as 50km's one. The last occurrence was in 2013. The largest one of 40km is M4.7 in 1925.       

Others are omitted.