Structure of the Proposed Site for the Superconducting Super Collider (SSC) in Northcentral Texas

Abstract

The SSC, a large (54 mi, or 87 km, in circumference) scientific instrument designed to accelerate, guide, and focus opposing beams of protons around an oval bedrock tunnel to collision, will be located near Waxahachie in northern Ellis County, Texas. Construction of the collider tunnel will involve excavation of three Upper Cretaceous rock bodies. From oldest to youngest, these are the Eagle Ford, Austin, and Taylor groups. Approximately 70% of the tunnel will traverse the 500-ft-thick (153-m) Austin Chalk. The site lies along the northeastward extension of the central Texas Balcones fault system, a zone of inactive, en echelon normal faults. In the SSC vicinity, most faults are generally straight to broadly curving and strike northeast to east-northeast. Dips of the larger faults range from 45{degree} to 80{degree} northwest or southeast. Displacements of the large faults range up to an estimated 100 ft (30 m). Some of the faults bound small, northeastward-trending grabens that are more than 2000 ft (610 m) wide and 3.5 mi (5.5 km) long. Features associated with the faults include (1) low (relief up to 40 ft, or 12 m) resequent fault-line scarps, (2) normal and reverse drag with strata inclined more than 40{degree} at places,more » (3) crystalline calcite fracture fillings with slickensides preserved on the outer surfaces of the fillings, and (4) broad (up to 1 mi, or 1.6 km, wide), northward-trending flexures that occur at some places. Joints present in the SSC vicinity are nearly vertical and usually reflect the local structure. Most structural features exposed along the collider path developed in response to sediment loading in the Gulf basin; the imposed stresses resulted in rotation and possible sliding of a large stratal mass gulfward.« less