The Regional Connector Transit Corridor (RCTC) Project is a 3-km (1.86 mile) underground light rail project in downtown Los Angeles, California being constructed by the Los Angeles County Metropolitan Transportation Authority (Metro). In addition to twin bored tunnels, the project will include 789-m (2,590-ft) long concrete box tunnels and three underground stations to be constructed by cut-and-cover construction. These underground structures will be buried within Holocene- to late Pleistocene-age alluvial soils and the Pliocene-age weak clayey siltstone or silty claystone of the Fernando Formation. The deepest station is about 32-m (105-ft) below the existing grade. Located in one of the most active seismic regions of the world, these underground box structures are being designed to withstand seismic loading resulting from vertically propagating seismic waves. Specifically, the box structures will be designed to withstand differential lateral movement (racking) resulting from the shear waves. As part of the preliminary engineering of the project, seismic analyses were undertaken. The analytical procedure and the results are presented demonstrating the current state of practice for seismic design of transit stations and box structures in Los Angeles. The analytical approach followed Metro's design guidelines. Design response spectra and earthquake time histories were developed for two risk levels using Probabilistic Seismic Hazard Analysis (PSHA) and spectral matching. A series of one-dimensional site response analyses were performed to develop a non-linear distribution of free-field displacement along the depth of each underground structure. The results, including time histories of free-field shear strains and horizontal ground displacements during the seismic events for the two risk levels, were used as input parameters to racking analyses to be used in structural response computations.