More than 100 aftershocks hit Japan after powerful quake that killed 13

The situation

People are being urged to stay alert, with earthquake aftershocks potentially reaching magnitude 7, officials say

What shifts

For those following 100, aftershocks, hit, japan, powerful, this report from BBC introduces a variable that could shift existing calculations.

The wider picture

Looking back, BBC and others have reported on the conditions that made more than 100 aftershocks hit japan after powerful quake that killed 13 possible.

Where this fits in Signal Ledger

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The editorial line

Signal Ledger reads this through the lens of 100, aftershocks, hit, japan, powerful: People are being urged to stay alert, with earthquake aftershocks potentially reaching magnitude 7, officials say.