Japan’s massive earthquake, tsunami and nuclear disaster is likely to be the costliest natural catastrophe on record but the impact on the private insurance industry probably will not surpass that of Hurricane Katrina in 2005.

Japanese insurance companies, global insurers and reinsurers, hedge funds and other investors in catastrophe bonds are all expected to bear a portion of the losses that seem likely to exceed $100 billion. Total damage from the 1995 earthquake in Kobe, Japan, was estimated at $100 billion, according to the Insurance Information Institute, but only about $3 billion of that was covered by insurance.

The greatest uncertainty surrounds contamination from the nuclear accident prompted by the earthquake and tsunami.Operators of nuclear plants in Japan are required to buy liability insurance through the Japan Atomic Energy Insurance Pool, an industry group. But they are required to buy coverage of only about $2.2 billion for liabilities, and the pool does not sell the utilities coverage for earthquake damage or business interruptions, suggesting it will again be up to the Japanese government to bear the brunt of those costs.

Until now, the most destructive earthquake in terms of property damage was the one that struck Northridge, Calif., in January 1994, when insurers paid out $15.3 billion, or $22.5 billion in today’s dollars.