WASHINGTON — Scientists examining movement along faults in Southern California said Wednesday that the region may be in for a series of earthquakes comparable to the Northridge temblor--or a single far greater quake--in upcoming decades.

Lucile M. Jones, a geophysicist with the U.S. Geological Survey in Pasadena, told a House committee that the Southern California Earthquake Center has looked at 150 years of quake data and concluded that there have not been enough quakes to explain all the shifting along faults.

Testifying at a hearing of the Science, Space and Technology Committee, Jones said the region has experienced "only one-third the number of large and major earthquakes" expected, given the rate of movement along faults.

"Where are the missing earthquakes?" Jones said. Her answer was that stresses accumulated inside the earth may be unleashed in the coming decades.

In Los Angeles, the executive director of the Southern California Earthquake Center said he was "a little bit aghast" that the conclusions were announced Wednesday, but he added that the findings are endorsed by scientists in the group. There is some disagreement, however, about the probability of quakes.

"We've reached a point now where our models are predicting more Northridge-type earthquakes or bigger earthquakes in the future than we've had in the last 150 years," said Tom Henyey, the center's executive director. The Southern California Earthquake Center was established by the National Science Foundation to improve the methodology for forecasting quake movement in Southern California.

Highlighting the lack of certainty in earthquake analysis, Henyey added that it is also possible that seismic stress has not increased. Scientists are still evaluating data for a detailed report to be released this summer, he said.

Nonetheless, the center's overall finding is consistent with concerns expressed by other scientists that the Jan. 17 Northridge quake may have been a forerunner, if not a foreshock, to a more intense temblor or a series of quakes.

Allan Lindh, chief of seismology for the Geological Survey at Menlo Park, said Wednesday there were one or two serious earthquakes in the San Francisco Bay Area each decade for 70 years before the catastrophic quake in 1906. He said that such a pattern--which has also been recorded in Japan and Russia--appears to be repeating itself in Southern California in recent decades.