Counts of occurrence per depth in 網走地方

Counts of occurrence per depth in 網走地方 (Abashiri region) is shown as below graph,

note : There are not included of all depths to avoid too complicated curves. 

• 1km (red)…This count of the earthquakes is the most one. But, the max Magnitude is M5.1 in 1938 (The max of it in this area is M6.5 of 10km in 1967). The increase was slow down after M6.5 (10km in 1967), and there was the longest silent term between 1975/2002. After it, the counts started rapid increasing in Jun/2004. It may be related with M7.1 (釧路沖地震) in the rapid increase of 1km 2004 as the sign of M7.1 even though the epicenter far from 網走地方. The increasing count of 1km is still continuing. There will be the next great earthquake more than M6 because of the accumulation of many earthquakes since M5.1 in 1938.   
  
• 10km (yellow)…The count is the 2nd after the rapid increase of 1km in 2004.  M6.5 in 1967 is the greatest one in this area, and there was the rapid increase of count over the count curve of 10km. But, as no greater one there has been, the count has been changed to 2nd by the rapid increase of 1km in 2004 related with 釧路沖地震. The count is still continuing. But, not so rapid against the one of 1km. So, the count can't follow up the one of 1km.
  
• 20km (orange)…The count is the 3rd after the rapid increase of 1km in 2004 also. There was the quick step up of the count after M6.1 of 30km in 1959, and then there was the rapid increase of the count in 1965. It was about 2 years before M6.5 (10km) in 1967. By this M6.5, the count has one more rapid increase. But, after it, there was the longest silent term of 38 years between 1978/2016. Still, no more occurrence in 20km.　  
  
• 120km-160km(gray)…The minor peak of counts per depth around 120km. And there was M6.1(160km) in 1997. So, there may be increase the counts of them.
  

Counts of occurrence per depth in 北見・紋別地方

Counts of occurrence per depth in 北見・紋別地方 (Kitama & Monbetsu region) is shown as below graph,

Colored labels show the data of Max Magnitude/depth/date/count per each depth.

There was only data of 1km before M5.1 (190km) in 1944. After the M5.1, the max Magnitude of all data had been broken the record of them as below,

• Max=M4.9 (  1 km) : 1919-1944
• Max=M5.1 (190km) : 1944-1966
• Max=M5.2 (250km) : 1966-1990
• Max=M5.4 (170km) : 1990-2025

10km (count=1) was occurred in 2007 after M5.4 (170km/count=1) and 170km (count=2) about 2 years later. 10km (count=2-9) was occurred in 2009 including M4.2 (10km/count=4, max of 1km). At the count=5 of 10km, it became the same one of 1 km. The common count may be the trigger timing of the rapid increase of 10km. After 2 long silent times of 4 years/5 years, the count of 10km increased rapidly again in 2023.  

Since of no record update in 1km there has been, M4.9 is still the max value in 1km data. 3 months later, the 2nd longest silent term of 1km finished by the count =6 of 1 km. After the 1st longest silent term (1926-1976) and the 2nd one (1976-2024), there might be occurred the rapid increase of 1km's count in the near future.

Counts of occurrence per depth in 宗谷地方・宗谷海峡

Counts of occurrence per depth in 宗谷地方・宗谷海峡 (Soya region & Soya Strait) is shown as below graph,

note : There are not included of all depth to avoid too complicated curves.

• 1km(red)…This count of the earthquakes is the most one. But, the max Magnitude is only M5.6 since 1932 (The max of it in this area is M6.1 of 340km/350km in 1951/1992). The counts had have been increased rapidly after the long silent terms of it. The longest one was between 1993/2008, and the rapid increase count of 1km/10km was occurred in 2009 (next year of the end of the longest silent term). The rapid increase of the count of 10km was also occurred with it of 1km in 2022. 10km's rapid increase had been started just before 1km's one. It seems to show the tendency of the bringing the earthquake energy to shallower depth. 
• 10km(yellow)…The count is the 2nd. In 2022 increase, the curve approached to the one of 1km. The max Magnitude of 10km is M5.4 in 2022. The count increase of 1km/10km was occurred by this M5.4.
• 20km(orange)…The count is the 3rd now. The longest silent term is between 1919-1998 (Japan Meteorological Agency had started the observation of earthquakes in 1919).  The curve crossed over 1km's one between 2000-2010, and 2curves were overtaking and being overtaken after it until M5.4(10km) in 2022.
• 30km(yellow green) …The count is 4th. But, the increase has stopped since 2016. After it, the longest silent term has become about 9 years. It may be the sign of the next big earthquake or the continuous earthquakes.
• 40km(green)…The occurrence was only M4.3 in 1978.
• 320km(gray)…The count is 5th. Even though the count is only 6, the max Magnitude is M5.9. 
• 330km/340km/350km(gray)…The counts are 1-4. The max Magnitude are M6.0/M6.1. M6.1(340km/350km) is the max value in this area. 

Counts of occurrence per depth in 上川・留萌地方

Counts of occurrence per depth in 上川・留萌地方 (Kamikawa,Rumoi region) is shown as below graph,

note : There are not included of all depth to avoid too complicated curves.

• 1km(red)…This count of the earthquakes is the most one. But, the max Magnitude is only M5.6 since 1932 (The max of it in this area is M6.5 of 260km in 1942). So, the max value should become more than M5.6. In 2022, M5.4 of 1km has been occurred as a series of earthquakes including 10km. This may be the sign of the next bigger one.
• 10km(yellow)…The count is the 2nd. Because of the coming closer to 1km curve, the linkage with it may become easier than before. The rapid increase began after the long silent terms of 1922-1955/1955-1986 (1st/2nd longest). There were the preceding sequences of 20km(orange) before them of in 1995/2004. Especially the one of them in 2004 was included with M6.1. Between 2 continuous ones, there was the long silent term of 1997-2002.
  
• 20km(orange)…The count is the 3rd. The remarkable increase began after the longest silent term of (1919)-1968 (Japan Meteorological Agency has no quantitative data before 1919).
• 30km(yellow green) …The count is 4th. But, the increase has stopped since 2016. After it, the longest silent term has become about 9 years. It may be the sign of the next big earthquake or the continuous earthquakes.
• 40km/50km…40km is only once. 50km is no record.
• Ohters…The count of 150km/160km(gray) are 5th. Except M6.1 of 10km, all the greater earthquakes were occurred in far deeper area of 180km/200km/260km. 

Because of keeping the order of depth in the counts as shallower ones more, the status of earthquake occurrence is more stable one especially in shallow area. But, the big earthquakes more than M6 must be occurred in shallow area (1km/10km/etc.) as the order changer of them. Because 1km's huge earthquakes are the one of the final release of the stocked earthquake energy of deeper area.    

 

Counts of occurrence per depth in 渡島・檜山地方

Counts of occurrence per depth in 渡島・檜山地方 (Oshima,Hiyama region) is shown as below graph,

1km's count was the most one before M't Usu's eruption in 2000. After it, 10km's one becomes the most. It was occurred after the longest silent term (almost seven years) of 1km earthquakes. 10km's curve increased also by it, and there had been increased between 1995/11-2000/3. The increase of 10km seems to be occurred by M6.3 (20km) in 1993/8. Addition to it, M6.3 in 1993 may be occurred M6.1 (120km) in 1992. They had performed one chain reaction. Long silent terms were often found on the curves of shallow depths like as in 1km/10km/20km especially, and the rapid increase of the counts are occurred after them with high accuracy. In curves of deeper ones, the interval themselves are long in general.  So, there should be difficult to be found out the longer silent term than it.   

Counts of occurrence per depth in 石狩・空知・後志地方

Counts of occurrence per depth in 石狩・空知・後志地方 (redefined rectangle area of Ishikari,Sorachi,Shiribetsu region) is shown as below graph,

Before M6.7 (1km) in 1947, there was earthquake swarm of unknown details in Jan/1944. After M6.7 and the aftershock, log of the counts of 1km occurrence is linear against the date.Before M6.7 of 40km in 2018, there was earthquake swarm of 30km in Jul/2017. There was long quiet period of 40km between 1947-2018 also. In 2017, the count of 30km preceded it of 20km.    
 

Counts of occurrence per depth (in 胆振地方)

In 胆振地方 just before M6.7 in 2018/9/6, Distribution of Depth (brown line) was as below,

After M6.7, the new peaks has grown up around 30-40km depth mainly. Before M6.7, there were the even peaks of 30km/130km. By M6.7, the peak of deep area has been shifted to shallow area. M6.7's epicenter was in 40km. If the epicenter were shallower more, the curve might have become more simple like as trapezoid with downhill in 三陸沖. The even peaks of 30km/130km seems to be the trigger of avalanche from the deep area to shallow area.

To make clear the relationship among the count changes per depth as  time sequence, I tried making the graph of Counts of occurrence per depth for the data in 胆振地方 as below,

Note : There are not all data of each depth. Some depth data are omitted.

Intersections among the lines between of the different depths seem to be the changing points of the pattern of the count curves per depth. Counts of 22 times of 4 lines of 20km(orange)/30km(yellow green)/40km(green)/130km(gray) are crossed in narrow area around the time of M7.6. Towards Year 2000, there was the first jump of 20km curve, the 2nd jump of 10km, and 3rd jump of 1km. The jumps had moved to deeper area to shallower area. The close-sets between 2 lines seem to becoming the changing patterns as like circled points. 

So, this graph may be useful for the prediction of the sudden increasing of counts (it may sometimes mean great earthquakes with many aftershocks). The long blank times until the next occurrence can be checked in the graph also. 

In 三陸沖, the graph of counts of occurrence per depth is as below,

The graph is more simple because of less depths.

Counts of 1km(red)/10km(yellow) have been overtaking and being overtaken. After jumping up, the line becomes flat, or tilted straight lines.The previous small jumping up were caused the next change in the other lines.