Banks' asset quality and their level of the provisions will come under further review after the most severe Canterbury aftershock yet yesterday afternoon, following the February 2011 quake. The South Island region of New Zealand experienced a less damaging quake in September 2010.Most Christchurch bank branches [tbc early Tuesday] will be closed today and may remain closed for the remainder of the week.ANZ National kept two branches in Ashburton open yesterday and they will be open today. BNZ said it will open two branches today, in Riccarton.ASB will have three branches open. Westpac's plans for its branches were not clear.New Zealand Post closed all its post shops in the city yesterday for an indefinite period, affecting all Kiwibank services.Many other businesses and public services are likely to be disrupted this week. The additional damage in the city, while less than in February, includes damage to physical infrastructure partly or wholly repaired in the four months since the last earthquake.Yesterday's event seems likely to accelerate the loss of population from the Canterbury region.Banks in New Zealand have provided uneven disclosure over the most recent financial reporting periods on the effect of the earthquakes on their businesses.ANZ said it considered provision coverage was "appropriate", though, it said, the "underlying individual provision charge may change over the short- to medium-term".In its March 2011 disclosure document issued late last month, ASB stated vaguely that, "Where appropriate, impairment charges have been recorded to write the asset down to the recoverable amount."Bank of New Zealand said it provided a NZ$60 million overlay to cater for losses.Westpac provided NZ$56 million. It said the Christchurch earthquakes had reduced cash earnings by NZ$40 million in the March 2011 half.Kiwibank said estimates needed to cover quake losses "are highly subjective, and loss estimates range from NZ$10 million to NZ$45 million."