Big Claims Expected From Trade Center Blast: The World Trade Center explosion was a catastrophe for the insurance industry, which expects large claims from companies unable to conduct business while the twin towers are closed, industry analysts said. Officials cannot estimate total damages until after the towers reopen because businesses continue to suffer losses, but insurers consider the explosion "a catastrophe." Said Ronald Krauss of the American Insurance Assn.: "We already know this is going to exceed the definition of a catastrophe, there is no question about that." The lack of even basic services, such as electricity and water, will keep the businesses closed for some time.