A giant fault hidden beneath downtown Los Angeles could cause highly destructive earthquakes, according to a recent discovery by one Harvard researcher and a colleague from California.

Assistant Professor of Structural and Economic Geology John H. Shaw and Peter Shearer, a professor at the University of California at San Diego, published their findings about the fault in Friday's issue of Science magazine.

The fault, which is composed of three segments, is about 25 miles in the east-west direction and 10 miles in the north-south direction, Shaw said.

Each of the segments is comparable in size to an adjacent fault in Northridge, Calif. that caused a major earthquake in 1994, he said.

Shaw said if any one of the three segments does cause an earthquake, it could be as destructive as the Northridge quake--which had a magnitude of 6.7, killed 33 people and caused $35 billion in damages, according to an article in The New York Times on March 5.

If all three segments were to rupture simultaneously, an earthquake about three times as violent as the Northridge disaster could occur, Shaw said.

Researchers already suspected the fault's existence, but it was not confirmed until oil companies drilling in the Los Angeles basin provided evidence, he said.

It is not known when the fault

might cause an earthquake, Shaw said.Scientists still need to find out when the stressbegan and whether it has been relieved by a pasttemblor, he said.

Shearer said they are still investigating theexact location and size of the fault because thereis a possibility that it is connected with othersto the east and west and possibly to another southof Los Angeles.

Finding connections between faults is difficultbecause the links may be too deep for seismictests, he added.

The discovery will be important in helpingscientists predict approximately when the nextearthquake will be and in preparing the city for apossible disaster.

According to Hooper Professor of Geology PaulF. Hoffman, Shaw is currently working withProfessor of Geophysics Jeroen Tromp to constructa computer model of the rock around the LosAngeles basin.

The model would aid in the locating of futureearthquakes and in identifying where damage wouldbe most severe, he said.

"The way that lives are saved and property issaved is through improving building codes anddeveloping emergency response contingencies," Shawsaid