… at around 9:05 PM Wednesday evening in Japan (local time) around 10 minutes prior to this entry. Yurekuru on my iPhone went off just around a minute before the quake hit; EEW (earthquake early warning or kinkyu jishin sokuho) works great in Japan.
This was a shallow quake at a depth of around 10km with its epicenter located off the eastern coast of Chiba Prefecture (the prefecture just east of Tokyo). Neighboring Ibaraki Prefecture experienced the greatest amount of shaking with one city (Kamisu) experiencing a 5+ (which is strong enough to cause property damage). One city in northeastern Chiba, Choshi, registered a 5+ while Asahi City registered a 5-.
And in case you are wondering, yes, the quake could be felt strongly in parts of Tokyo as well (more so if you were in a tall building at the time), even though most locales were a 3 on the JMA seismic intensity scale. No tsunami was generated (tsunami shinpai arimasen).
What’s interesting is that earlier, two large offshore quakes struck off the Sanriku coast (i.e. the Tohoku region where last years M9.0 quake occurred). The first one was quite big; there was a M6.8 at 6:14PM off Hokkaido (though the max seismic intensity on land was only a 4 in places like Iwate Prefecture and Aomori Prefecture) and a M5.9 at 7:55PM. The quake off Hokkaido did generate a small tsunami of around 20cm (observed at the port of Hachinohe in Aomori) and was felt as far as Shizuoka Prefecture (could also be felt in Tokyo).
On NHK News Watch 9 (which was what was broadcasting at the time), one of the analysts brought up a graphic of the Japan trench and showed these 3 large quakes taking place along the trench. What was more striking was the graphic (below) he showed overlaying the area where last March’s massive quake took place. This evenings quake off Chiba was at the tail end of that area while
the earlier one off of Hokkaido was at the opposite end. In otherwords,
these two M6+ quakes while on their own, could be considered big
quakes, are likely an aftershock from last years M9.0 quake.
Enough “excitement” for the day… off to bed… おやすみ…
