They're not "banking with zero reserves"; they're just banking under a different and more complicated set of regulations on those reserves than that one simple

They're not "banking with zero reserves"; they're just banking under a different and more complicated set of regulations on those reserves than that one simple ratio. In principle that's a better and finer-grained set of regulatory tools, though it obviously didn't work too well for the SVB. The SVB's problem was that they were allowed to ignore the mark-to-market losses on their long-term bond-like assets when interest rates increased, because they said they were going to hold them to maturity. That let them keep gambling that their losses would reverse, instead of raising capital after they became MTM undercapitalized but before they became insolvent. I'm not an expert here, but as far as I know the reserve ratio would have accounted for those assets in the same way and had the same problem.