University reps hope that a $321 million unique, flexible retrofit, designed by a team of structural engineers, seismologists, and geologists, will keep things from getting any worse. They’re cutting two sections of the seating bowl into free-floating surface-rupture blocks that should move without crumbling even if the earth below shifts up to 6 feet.

The press box is also getting a redesign: Engineers calculated that a bad tremor could chuck the 1,000-ton structure onto the 50-yard line, so a combination of cable-laced concrete support walls and king-size shock absorbers was added keep it attached and upright. The new and improved stadium is scheduled to reopen in the fall of 2012, in time for a tectonic event: the annual Big Game against Stanford.

1. Concrete Core Walls Prestressed with a force of 1,900 tons and embedded with more than 10 miles of steel cables, the walls under the press box will act like springs to pull the structure back into place if it shifts.

2. Shock Absorbers Sixteen 5-foot-long shock absorbers filled with silicone fluid are located between the core walls and seating area, exerting a force of 220 tons each to keep rocking to a minimum.

3. Concrete Piers Concrete piers are designed to absorb quake damage and keep the western seats from collapsing. (The eastern side is shored up naturally—it’s built into a hillside.)

4. Sand Layer A 3-foot-thick layer of sand will smooth out an abrupt vertical shift of up to 2 feet.

5. Plastic Sheeting Buried in the sand, two layers of high-density polyethylene (about ¹/₁₆-inch and ³/₈-inch thick) provide a slippery surface for the rupture blocks to move.

6. Stone Columns Subterranean stone columns help bolster a weak layer of underlying soil.

Authors: Julian Smith

to know more click here