(Adds details on acceleration, no critical alerts, home access)
By Laura Zuckerman
April 18 A slow-moving landslide threatening the affluent Wyoming community of Jackson is picking up speed, with safety concerns prompting authorities to halt efforts to stabilize the area, city officials said on Friday.
"The acceleration in the slide has been doubling since approximately April 1st, with significant movement in the last 24 hours," the town said on its website. But officials were not issuing any warnings or critical alerts, it added.
The landslide has displaced residents of several homes and two apartment buildings near the base of the East Gros Ventre Butte, which geologists said was slumping at a rate that this week increased to a foot (30 cm) a day from four inches (10 cm).
"The fractured mass wants to slide down and gravity is pulling it down," said Peter Ward, a retired geologic hazards expert with the U.S. Geological Survey.
"How it's going to fall apart nobody knows, but it's going to come apart," Ward said at a town meeting.
Evacuations from residences and several businesses below the crumbling hillside may continue for weeks as Jackson crews and utility companies work to prevent ruptures to gas and power lines and a city water main.
Water supply was halved pending repairs set for Tuesday, when water would be shut off to several Jackson residences and businesses until the repairs were completed, authorities said.
Dozens of people who wanted to return home on Saturday to retrieve possessions were allowed to do so with escorts, Jackson officials said in a statement. Homeowners will also be allowed access to their homes on Sunday, officials said.
Some residents in the evacuation advisory area near the slide who chose to remain were advised that they entered the area at their own risk, the officials added.
An effort this week to buttress the base of the butte was halted on Thursday as rocks and gravel rained down, Jackson Police Lieutenant Cole Nethercott said.
"Right now, it's a life safety issue," he said.
The slide, about a mile (1.6 km) from downtown Jackson, has cracked retaining walls, opened fissures in roads and bulged pavement, Ward said.
A retaining wall behind a Walgreens pharmacy had been breached with gravel and rocks tumbling into its parking lot, pictures on Jackson's official website showed.
Officials plan a Town Hall news conference on Saturday morning.
While landslides are common in the towering Teton Range near Jackson, best known as an international ski destination and for homes owned by celebrities such as actress Sandra Bullock and former U.S. Vice President Dick Cheney, they are rare in developed areas, Ward said.
Possible factors in the slide may be historic excavation of rocks and gravel at the toe of the butte, a major water leak in 2011, land development, recent rains and snow melt, he added. (Reporting by Laura Zuckerman in Salmon, Idaho; Editing by Barbara Goldberg, Mohammad Zargham and Clarence Fernandez)