Justin Sullivan/Getty Images
- Ratings agency Moody's has put First Republic and Western Alliance under review for possible downgrade.
- Shares in the regional banks cratered Monday as Silicon Valley Bank's collapse rattled markets.
- The agency warned six institutions could suffer bank runs that could stop them repaying their debts.
Moody's Analytics has put First Republic and Western Alliance on review for a possible downgrade as the sudden collapse of SVB threatens the health of regional US banks.