Geologists Suspect Landers Quake Triggered Anaheim Slide : Disasters: Another slippage during recent storms, in Laguna Beach, is attributed to a reactivated landslide.

Geologists suspect that the devastating Anaheim Hills landslide might have been triggered by the 7.4-magnitude Landers earthquake in June, Anaheim city spokesman Bret Colson said Wednesday.

Also Wednesday, geologists in Laguna Beach released a report concluding that the mudslide there, which destroyed three homes, was caused by an ancient, reactivated landslide.

Colson said geologists have linked the June 28 quake to the 25-acre landslide in Anaheim because it was around that time that residents in Anaheim Hills started reporting cracks in streets and sidewalks.

“The timing of the incidents are too much for coincidence,” Colson said. “The homeowners first reported the problems in July, but had been noticing damage before that. . . . It coincides with the time of the Landers earthquake.”

The 25 acres are part of an ancient landslide area, geologists believe.

Similarly, in Laguna Beach, a report prepared by a geological consultant also cited the reactivation of an ancient slide area as the cause of the Jan. 19 mudslide that destroyed three hillside homes on Mystic Lane. One of those houses crashed 50 feet down a steep ravine and caught fire after it tangled in utility lines.

Officials of both cities said their geologists believed that the pounding of continual rainstorms that lasted almost three weeks accelerated the ground slippage.

Colson said geologists are considering “many theories, but (the Landers earthquake) is the one that they said they wanted to look into.” He cautioned, however, that the theory is “still very preliminary.”

He said the geologists briefed city officials about the theory but could not discuss it publicly, on the advice of the city attorney, who is concerned about future lawsuits.

Between July and January, the Anaheim landslide area moved about one inch. But in the past three weeks, the slide has moved as much as 15 inches in some areas.

The severity of the slide has forced the evacuation of 46 homes. Residents have been instructed to stay away from their homes until the movement is stabilized.

In Laguna Beach, aerial photographs and geological fieldwork detected the ancient landslide in the upscale ocean-view neighborhood. Geologists reported that they remain uncertain how far that ancient slide extends beyond the damaged area.

“There is a possibility that the ancient landslide area is larger than that currently reactivated,” according to the report prepared by Geofirm, the company the city hired to investigate the disaster. The report cautions that the landslide may underlie at least one other home on Mystic Lane.

The report stresses that “assessment of the future stability of all properties around the recently active landslide is beyond the scope of this investigation.”

Contributing to the disaster, the report states, is the fact that the strata of earth beneath and next to the ancient landslide slant in a way that “tends to promote gross slope instability.”

The report said there was no evidence of defective, leaking storm drains or sewers that might have prompted the landslide.

Iraj Poorman, spokesman for Leighton & Associates, an Irvine firm hired by Farmers Insurance to determine the cause of the slide, said its geologists have reached virtually the same conclusions.

As part of its recommendations to the city, Geofirm has urged the razing and clearing of slide-damaged homes on Mystic Lane as soon as possible and “winterizing” the slopes by filling cracks and diverting the drainage of surface water away from the area. The report also recommends monitoring the demolition of those homes and additional studies to determine ways to stabilize and redevelop the lots.

Of the Anaheim Hills landslide, Martin Stout, a professor emeritus from Cal State Los Angeles and an expert in geological sciences, said he doubted whether the reactivation of the landslide was linked to the earthquake, which was centered about 100 miles northeast of Anaheim.

“It’s not a very good proposition,” Stout said. “It’s possible, but it’s not a very common occurrence. It’s not as common as people believe, including geologists.”

Stout said a more plausible explanation for the reactivation would be underground water.

“Even before the rains, there could have been a lot of water in the hills from people watering their lawns or from other things,” he said.

He added that the majority of landslides are caused by water, not seismic activity.

“Large landslides usually occur during wet cycles . . . water is the much more likely scenario,” he said.