If bank foreclosure auctions occur weekly then why are there 93 foreclosure properties for auction in my zip c?

Your guess is wrong. Realty Trac adds them to its lists as soon as a foreclosure auction has begun. It takes MONTHS after the initiation of the foreclosure auction before all is said and done, and the house is actually auctioned. Thus they will not 'clear out' until they have actually reached the auction phase.

Typically, foreclosure auctions occur once a month in each county. Of course, that might change depending on the number of properties in foreclosure, but once a month is standard. Sometimes a notice of foreclosure will be entered at the courthouse, but it could just announce a future auction date - there are all types of scenarios.

Most properties that aren't auctioned off are given back to the banks who then use real estate agents to put the homes back on the market to sell. These are called REO properties.

If you are looking to purchase foreclosure property, note that they don't always offer a great deal, especially if you're a real estate investor. In addition, you usually don't get to see them before they are auctioned off. Pre-foreclosures and motivated sellers offer more of a discount on their purchase price.