TOKYO-Japanese property owners, already reeling from a series of typhoons and a deadly earthquake, may be spared a separate blow from insurers.

While the natural disasters that have pounded Japan this year are costing insurers billions of dollars, the losses probably won't be enough to cause significant increases in property rates.

So far, an earthquake that struck Niigata Prefecture in late October and 10 typhoons that swept across the island nation this year are estimated to have cost insurers between $6 billion and $10 billion. While damages from last month's earthquake are still being assessed, EQECAT Inc. is projecting insured losses of $2 billion to $5 billion caused by the temblor.

Catastrophe losses will climb further when claims from Typhoon Tokage are counted. The deadliest typhoon to hit Japan in over a decade, Tokage's wind and heavy rains triggered mudslides and flooding that left at least 63 people dead as it moved across the country on Oct. 20.

Insurers and property owners last week were totaling damages from the Niigata earthquake, which could be more expensive than the one that struck Kobe in 1995, killing more than 5,000 people and leaving insurers with around $3 billion in claims. The Oct. 23 earthquake has left at least 31 dead and injured more than 2,000. Severe aftershocks from the quake that measured 6.8 on the Japan Meteorological Agency's seismic intensity scale have added to the damage.

Among the commercial losses from the Niigata quake was the first-ever derailment of several cars of Japan's Shinkansen high-speed railroad. Service is expected to be disrupted for several weeks as damages are assessed.

"The damage in Kobe was significantly greater," said Rick Clinton, president of Oakland-based EQECAT, a subsidiary of risk management consultant ABS Group Inc. of Houston. But insured damages from the quakes, though nine years apart, are similar, he said. That is because even though insurance covers a small percentage of property in Japan, it is more prevalent now than when the Kobe earthquake struck, he explained.

The Niigata quake is likely to result in total economic losses far lower than the Kobe quake, which created economic damages of $100 billion, he said.

Despite the billions in natural disaster losses in Japan this year, no one is predicting large increases in coverage costs for property owners in Japan.

"Certainly a single event is not going to cause them major concern or heartache," said Mr. Clinton, referring to insurers' likely reactions to the recent earthquake. Taken with other catastrophes on a global basis, though, some pressure on prices could eventually come to bear, he said.

Domestic insurers have been "very conservative about pricing and careful about accumulating catastrophe reserves," said Runa Ichihari, director of insurance ratings at Standard & Poor's Tokyo office. "In terms of ratings and credit quality, we don't think the series of typhoons will result in a significant impact on nonlife insurance companies."

As for the potential for rate increases, Ms. Ichihari said insurers likely will wait until they have a clearer picture of their financial condition when their fiscal years end next spring before making decisions on whether to raise insurance prices.

Only around 11% of property owners in Niigata have earthquake insurance, which will limit insurers' losses, according to Tomishi Ishida, an insurance analyst with Goldman Sachs Asset Management Co. Ltd. in Tokyo. Earthquake insurance is written as an extension of fire insurance in Japan and rates for the fire coverage could go up, he said, although he could not predict how much.

Japan-based insurers are taking big hits from the catastrophes and the losses also are showing up on foreign insurers' books.

Millea Holdings Inc., the Tokyo-based parent of Tokio Marine & Nichido Fire Insurance Co. Ltd., reported that five of the typhoons and two heavy rainstorms are costing the company $797.5 million before reinsurance recoveries.

American International Group Inc. also has been affected by the typhoons. Three of the storms, along with losses from four hurricanes that struck Florida this year, are expected to cost AIG $500 million to $515 million in after-tax losses. The insurer did not specify how much of the loss would be attributable to the storms in Japan.

A spokesman for Munich Re Group said the group's reinsurance operations expect losses of around $635.3 million from two of the typhoons and the Atlantic hurricanes.

Those losses are not expected to cause a jump in treaty renewal prices, he said. As for upcoming renewals, Munich Re expects current pricing and conditions to remain "stable on the whole," according to the spokesman.

Munich Re does not expect significant losses from the earthquake, he said, because most residential buildings are not insured for the risk and the Japanese government operates an earthquake reinsurance facility that will pick up some of the losses.

Property owners in Japan may actually have been spared worse damage from the typhoons because the storms weakened considerably before reaching land, according to Jayanta Guin, vp of research and modeling for AIR Worldwide Corp., a Boston-based unit of Insurance Services Office Inc. in Jersey City, N.J.

And, Mr. Guin noted, typhoon losses of around $5 billion during the storm season from March through December are not highly unusual and can be expected to occur around every seven years. A $6 billion loss is generally a 10-year event, Mr. Guin pointed out.

The number of storms that have sprung up in the Pacific is "not very unusual," Mr. Guin said. "What is a little unusual is that 10 have made landfall in Japan." That number of landfalls is considered a 140-year event, he added.

David Snyder, vp at the American Insurance Assn. in Washington, said that weather conditions like those that spawned the spate of Atlantic hurricanes and Pacific typhoons in Japan have to be studied to determine whether they can be corrected. If the conditions stem from a cause, such as global warming, that can be addressed, "everyone, including insurers, will have to examine these challenges," he said.

"It behooves everyone to take a look at preventative measures," Mr. Snyder said of ways to determine if weather trends are changing and if they can be manipulated.