Wu said he was informed that California Bank announced it had agreed to acquire PacWest Bancorp, according to the Wall Street Journal. PacWest has been at the center of concerns about the region's banking system. Bank of California shares also fell sharply. But both banks have weathered the recent turmoil in relatively good shape, and both stocks have rebounded. PacWest lost 18% of its deposits in the first half of the year, while California banks lost nearly 4%. PacWest…