Assessment of Fault-Creep Deformation at Memorial Stadium, University of California, Berkeley, California

Memorial Stadium, at the University of California, Berkeley, seats more than 70,000 spectators, houses the athletic department offices, and is eligible for inclusion in the National Register of Historic Places. The stadium is scheduled for structural modifications as part of a seismic retrofitting program. Several parts of the stadium have suffered structural distress, the most extensive of which appear to be associated with creep along the Hayward Fault, which longitudinally bisects the stadium from end zone to end zone. To assess the location, extent, and nature of structural distress and deformation, we mapped fracturing and other forms of structural distress throughout the stadium. Fracturing in the stadium appears to be a result of at least four mechanisms, which, in increasing order of occurrence, are 1) separation and spalling, resulting from poor construction practices; 2) differential settlement; 3) expansion or contraction induced by heat of hydration and curing effects; and 4) creep along the Hayward Fault. The majority of fractures induced by fault creep are in Sections A, XX, and X at the northern end and in Sections KK, L, and LL at the southern end. Additional structural distress includes tilting of structural columns between the mezzanine and seating levels and rotation/separation of the stadium walls at an expansion joint. Delineation of creep-damaged areas provides a useful benchmark for structural remediation of creep-induced damage. In addition, analysis of fracturing and deformation patterns provides strong constraints on the location and width of the active creeping trace of the Hayward Fault beneath the stadium.