Distribution of Depth in 長野県北部

Distribution of Depth in 長野県北部（Northern Nagano Pref.）

Most of  "Matsushiro Earthquake Swarm" since 1965 are recorded as "unknown" with no magnitude data. They are counted as 1km in my blog as same as other area. So, the 1km's count almost become 10,000 times far more than 10km's one. In most areas with enough data, the both count of 1km/10km tend to become almost same counts. Or, 1km's count tend to become more a lille bit than 10km's ones. This case is abnormal one.