By the context, it seems to me like 弱 is a counter for degrees on the richter scale (and perhaps other things). Am I getting this wrong? So that’s the first question.
On the second question: It seems to me like a weird kanji for counting earthquake strength. Maybe the richter scale being logarithmic has something to do with it. That would make it weak in a sense (compared to a linear scale).
If anyone could shed some light on this, I would appreciate it.