The earth moved again near the site of the 1989 northern California earthquake, and seismologists not only predicted the tremor - they caused it.

Hoping to learn more about the area's fitful geology, government scientists set off a half-dozen explosions 80 to 100 feet below ground Tuesday near the epicenter of the quake, creating a shudder registering 1.3 on the Richter scale.The experiment in the mountains 20 miles east of Santa Cruz was conducted shortly after 11 p.m. to avoid disturbing people.

Jeff Wood, who lives nearby, said he didn't feel the tiny quake. But he heard the explosions.

There was no danger the fake quake would trigger a real one, scientists said.

The experiment occurred near where a 7.1-magnitude quake occurred on Oct. 17, 1989, on the San Andreas fault. The quake killed more than 60 people and collapsed a double-decker freeway in Oakland.

Seismologists said studying the velocity of the sound waves sent through the fault by the explosions should help them gain a better understanding of the area's geologic structure.

They also said the experiment would help them check their monitoring instruments.

It will take several months for scientists to interpret all the data.