SENDAI, Japan—Insured damage estimates from the earthquake and tsunami that ravaged northeastern Japan reached as high as $35 billion, catastrophe modelers said last week.

The quake and tsu-nami left thousands dead and hundreds of thousands homeless. Complicating the rescue and recovery efforts was damage to nuclear reactors.

In assessing losses in the March 11 disaster, Boston-based catastrophe modeler AIR Worldwide Corp. last week estimated that insured property losses would range from $15 billion to $35 billion.

In a statement accompanying its preliminary estimate, AIR said it had simulated dozens of scenarios with varying magnitudes, focal depth and rupture width.

“The losses are most sensitive to rupture dimensions, and become extremely large if the modeled rupture is extended southward towards the Tokyo and Chiba prefectures, which contain a higher concentration of insured properties,” AIR said in the statement.

AIR said its Japanese earthquake model did not account for the effects of the resulting tsunami.

In its estimate last week, Oakland, Calif.-based catastrophe modeler EQECAT Inc. projected that the catastrophe would cause between $12 billion and $25 billion in insured property damage.

EQECAT's analysis broke down losses by line of business, saying it “encompasses the effects of earthquake shaking, ensuing tsunami and fires, and losses to automobiles, marine, life and personal accident lines.”

According to EQECAT, the largest component of insured losses will be covered by the property insurance market. In a breakdown of losses by line of business—excluding losses associated with the ongoing nuclear emergency at power plants in the affected area, EQECAT estimated that earthquake shake losses will range from $8 billion to $15 billion, with about 25% ceded to Japanese Earthquake Reinsurance Co. Ltd. Automobile losses will reach as high as $1 billion; marine losses, $1 billion to $3 billion; life insurance losses, $2 billion to $3 billion; and personal accident, $1 billion to $2 billion.

In a webcast last week, Kent David, EQECAT's manager-consulting services, said the catastrophe caused significant damage to infrastructure in Honshu that would affect Japan's ability to rebuild and recover economically. For example, the disaster created gaps in the country's industrial pipeline for products such as semiconductors. The resulting contingent business interruption losses are extremely difficult to model and, therefore, are not modeled, he said.

A colleague of Mr. David's called the event a “black swan,” meaning an extremely rare, unforeseen event that had extraordinary consequences. “We need to get black swan events” into catastrophe models, said Paul Thenhaus, senior seismologist at EQECAT.

Clive Nicholls, a London-based vp with Crawford & Co.'s global markets unit, said the event differs “severalfold” from earthquakes the claims adjuster has faced previously in terms of severity of the earthquake and tsunami as well as the radiation threat.

He said Crawford had staff on the ground in Tokyo, and had set up a hub in Singapore with Japanese-speaking personnel to help clients. “It's about the worst combination of logistics that you can imagine. You simply have to keep talking to our people locally and wait until it's safe, whenever that might be,” to launch the adjustment process.

Mr. Nicholls said the “massive disruption of the supply chain” could lead to significant contingent business interruption claims globally. “Because of no access, it's too early to understand the full repercussions,” he said.

“The consensus seems to be building that the significance seems to growing by the hour,” said Howard Mills, director and chief adviser of Deloitte Services L.P.'s insurance industry group in New York. He said as of last week, the losses did not seem to be large enough to harden the market. But he said loss reserves are beginning to drain, and that the Japanese losses could be a precursor to a subsequent “substantive event” that will begin hardening the market.

Although the extent of total losses won't be known for some time, several insurers and reinsurers began issuing estimates of their losses last week.

“The ultimate amount of insured losses from this event, as well as the market participants that will bear them, will depend on the types of coverage provided, the amount of reinsurance purchased and the structure of reinsurance programs,” according to Moody's Investors Service Inc. analysts James Eck, a vp and senior credit officer in New York, and Kenji Kawada, a vp and senior analyst in Tokyo.

In a statement, the Moody's analysts said “an additional wild card is the potential for business interruption losses, which are influenced by damage to power and transportation infrastructure.”

“We believe that estimating claims will be a protracted process,” the Moody's analysts said.

Insurers most likely to be affected by losses are domestic Japanese companies, Japan Earthquake Reinsurance Co. Ltd., international insurers, global reinsurers and Lloyd's of London companies, retrocessionaires and catastrophe bond issuers, Moody's said.

Paris-based reinsurer SCOR S.E. said it believed that its maximum pretax loss from the earthquake and tsunami would be e185 million ($257.2 million). It said its preliminary view was that losses likely would be less than that total.

Australian insurer QBE Insurance Group Ltd. said it estimated its net claims from the earthquake and tsunami to be $125 million.

“The majority of our estimated net claims from the devastating Japanese earthquake will come from the relatively low exposures in our reinsurance, marine and energy operations in Europe,” said Frank O'Halloran, CEO of QBE, in a statement.

Zurich-based insurer and reinsurer ACE Ltd. said its initial estimate of losses from the Japan earthquake was $200 million to $250 million.

A spokesman for Lloyd's of London said it was too early to estimate the size of the loss that the market might face, dismissing reports that it could be as much as £31.7 billion ($50.99 billion).

A market source who asked not to be named said an estimate of about $3 billion in losses for the Lloyd's market as a whole “sounds plausible.”

“While we expect this loss to be significant, it is still too early to provide a reasonable or reliable estimate considering the fluidity of the situation,” Joseph V. Taranto, chairman and CEO of Hamilton, Bermuda-based Everest Re Group Ltd., said in a statement. “Nonetheless, given the strength of our balance sheet and our core earnings, we have ample capacity to withstand the events that occurred during the first quarter and to continue to support our clients.”

Pembroke, Bermuda-based RenaissanceRe Holdings Ltd. said on its website that its “current initial assessment is that the net negative impact of the Tohoku earthquake on the company's results will be significant and is likely to be material.”

“We insure several hundreds of locations in Japan, but we don't have a loss estimate yet,” said Jon Hall, executive vp of Johnston, R.I.-based Factory Mutual Insurance Co., which does business as FM Global. “The primary reason is the nuclear radiation situation and the infrastructure issues. We've talked to 165 facilities and we know some have damage, but until you physically can see things, you can't get an estimate.” He said some locations have reported that they sustained no damage.

He said such events result in “creep in numbers” as losses mount.