We are undertaking a major deployment of digital seismograph systems from the EarthScope/USArray Flexible Array instrument pool to investigate the deep structure of the Sierra Nevada mountain range in Eastern California. Forty seismographs will be deployed in two configurations over a 30 month period. The first deployment is a two-dimensional array with about 25km station spacing. This array will be embedded with in the EarthScope/USArray "Transportable Array" footprint. The 70km spacing of the transportable array over a broad area of California and Nevada during their deployment will provide constrains on the regional earth structure. The scientific goals of their experiment include identifying the existence of high density crust and mantle material that may have recently foundered, or delaminated, from the overlying crustal material. This will constrain major hypotheses regarding the evolution of the continental lithosphere. If material has foundered, the constraints that they develop about the deep earth structure, through analysis of seismic waves and wave speeds, will be important information in the development of models to explain the physical and chemical consequences of this process.
