Topics: Banks, Bank Capital Requirements Summary: Credit Suisse Group AG's emergency merger with UBS Group AG will wipe out the bank's riskiest bonds, rattling investors in the quarter-trillion-dollar market for similar bank debt. About 16 billion Swiss francs, or about $17.3 billion, of the bank's additional tier 1 bonds will be completely written down, Switzerland's financial regulator, Finma, said in a Sunday statement. Credit Suisse also said it was informed by Finma that the bonds would be "written off to zero." Questions: - What are AT1 bonds? - Why have banks liked issuing them? - Why have investors liked buying them? - What is unusual about the Credit Suisse AT1s being written off