Implication of 2004 mid Niigata earthquake
In mid Niigata region, shallow local earthquakes were repeatedly occurred so far and gave damages in a relatively small region. As an example, in the case of 1961 Nagaoka earthquake (M5.2) , severe shaking of intensity-6 class was experienced only in a limited area of 3km diameter. Five persons were killed by this earthquake but only slight damages were reported at central Nagaoka city which was apart from the epicenter by 2km.
In the Japan Sea side region, large earthquakes of magnitude around 7 or more including "2004 mid Niigata earthquake" occurred as follows. (Fig.1)
- 1940 Off Cape Kamui M7.5, death of 10
- 1993 SW off Hokkaido M7.8, death of 202
- 1983 Japan Sea M7.7, death of 104
- 1964 Niigata M7.5, death of 26
- 1828 Sanjo M6.9, death of 1443
- 2004 Niigata Cyu-etsu M6.8, (this time)
- 1847 Zenkoji M7.4, death of several thousands
These earthquakes seem to align along a belt. The belt is considered as a zone of strain concentration within the Eurasian plate or the nascent collision boundary (Fig.2) of the Eurasian and the North American plates.
- Fig.1 ^TOP
- Fig.2 ^TOP
