housing margin calls, page-14

Lescat, not wanting to take all your valuable time but let's start from scratch...basically I'd replied to this

"Looks like the big end of town in Mandurah WA is getting margin calls on home loans, seems banks want to reduce their exposure to the 1.5 mill + market down there."

Questions..

what inspired these margin loan calls?

what would put property in jeopardy if the bank l/v was within banks guidelines?

how can a margin loan be called in if there's no trigger?

therefore what was the trigger?

why were these margin calls all in the same area?

please enlighten..