然而，在石棉县发生的一次强烈地震被发现，此次地震发生在约16万或17万年前。
However, a trace of a strong earthquake occurred about 16 000 or 17 000 years ago has been found in Shimian.
这是周一当天发生的余震中最为强烈的一次。
It was the strongest in a number of tremors felt throughout Monday.
之后一天都余震不断，最强烈的一次余震发生在当地时间下午5：30。
There were aftershocks throughout the day including a powerful tremor at about 5.30pm local time.
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