A powerful earthquake capable of causing widespread destruction is 99 percent certain of hitting California within the next 30 years, scientists said Monday.

A new model devised to determine the probability of major earthquakes has found that the chances of a 6.7 magnitude earthquake not hitting California by 2038 was one percent, the US Geological Survey said.

The chances of a monster quake, measuring 7.5 or greater, were predicted at 46 percent over the same projected period, with densely populated southern California most likely to be affected.

The predictions were the result of a new system that combines information from seismology, earthquake geology, and precise measurements from the earth's surface, allowing the probabilities of a major earthquake to be forecast.

"It's near certainty that we are going to have a potentially damaging earthquake somewhere in the region in the next 30 years," said Ned Field, chair of the Working Group on California Earthquake Probabilities.

"This new, comprehensive forecast advances our understanding of earthquakes and pulls together existing research with new techniques and data," Field told reporters in Los Angeles.

The earthquake forecasts, known as the "Uniform California Earthquake Rupture Forecast (UCERF)," were developed by Field's working group of scientists and engineers.

The group found that two of California's largest cities -- Los Angeles and San Francisco -- were more than 63 percent likely to face a 6.7 quake.

A 6.7 earthquake in Los Angeles in 1994 left 60 people dead and did an estimated 10 billion dollars damage, while a 6.9 quake in San Francisco in 1989 claimed the lives of 67 people.

Geologists say one of the biggest areas of concern in California is the southern section of the San Andreas fault in Riverside County, east of Los Angeles, which is described as being "10 months pregnant."

"You have to realize this is a very long pregnancy, and it is way overdue," said Southern California Earthquake Center director Tom Jordan.

Geologists say the fault erupts with a large earthquake ever 150 years or so, but has not relieved tension in 300 years.