Tsunami waves generated by a large offshore earthquake would threaten at least 1 million coastal residents in California and inundate the nation's largest port complex, according to a new report.

The bleak study being released Monday found gaps in the state's readiness to handle a tsunami, including flaws in the existing warning system, lack of evacuation plans by coastal communities, and building codes that don't take into account tsunami-strength surges.

In addition, many residents are unaware of the potential danger of tsunami waves and wouldn't know how to respond, the report said.

"I don't think we're ready yet, but we're getting there," said Richard McCarthy, executive director of the California Seismic Safety Commission, which issued the report. The commission, an independent advisory panel, formed a special committee to look at the dangers after last December's deadly tsunami in Southeast Asia.

In the past century, more than 80 tsunamis — mostly minor — have been recorded or observed along the California coastline.

The most deadly was in 1964 when a magnitude-9.2 earthquake in Alaska generated massive waves that killed 12 people.

Scientists have also kept a close eye on a 680-mile fault 50 miles off the West Coast that behaves much like those that produced the 1964 Alaska quake and the Southeast Asia tsunami that killed more than 176,000 last year.

While catastrophic tsunamis rarely strike the West Coast, state officials are acutely aware of the potential for damage and loss of life as a result of booming development along the coastline.

About a million people live in low-lying coastal areas that are vulnerable to flooding by a tsunami. Existing building codes call for structures to be able to withstand severe shaking from an earthquake, but the report revealed that homes and businesses are rarely designed to hold up against tsunami-force surges.

The report also found most coastal communities lacked evacuation plans for residents because of funding problems.

The state Office of Emergency Services and the University of California have produced inundation maps that show the coastal areas most at risk, but few communities have used them to map out and mark evacuation routes, the report found.

Along with threatening lives and property, a giant tsunami would strike an economic blow to the state, given the vulnerability of its ports, the report said.

If a tsunami shut down the ports of Los Angeles and Long Beach for two months, the economic loss could reach $60 billion. The ports make up the third busiest port in the world, but its docks and terminals are only about nine feet above the water.

A massive wave higher than that could cause extensive damage, the report said. Thousands of pleasure boats and other crafts could come loose, and vehicles, equipment, containers and tools could get washed away.

In June, a tiny tsunami off the far Northern California coast exposed just how unprepared the region was to the threat.

Cities were confused by the differing tsunami warning messages that came from two centers operated by the National Oceanic and Atmospheric Administration. Since then, federal, state and local officials have met several times to agree on the best way to alert communities — an action that won praise from the authors of the report.

A joint program by the NOAA and Federal Emergency Management Agency is also working on design guidelines for tsunami shelters that could extend to strengthening hospitals and other facilities as well.