9725766 Wernicke It is unclear if intracontinental plate boundaries, usually expressed as wide zones of diffuse deformation, behave as a system of microplates, or as a continuum. The Great Basin is a prime example of an area that behaves in this way. To determine if the observed strain pattern of today reflects a microplate trend, an 18 station GPS network has been established and has been operating for one year. This award provides an additional three years of funding to complete a total of four years of monitoring the network. After such time, the rate uncertainties will be sufficient to distinguish between microplate and continuum behavior. The basic scientific question to be solved will be a better understanding of intracontinental plate boundaries. This understanding is a fundamental concept to add to our knowledge of plate tectonics. In addition, the seismic hazard of such areas may be further quantified. To such an end, it is important to know if intraplate strain is localized within seismic belts, or if seismicity migrates secularly across a wide zone of relatively uniform strain accumulation. To solve this question, the Principal Investigator is using a series of GPS stations to compute yearly displacement in mm/yr and its distribution. From this, stress and strain can be calculated and the stress field examined to answer these questions. ***
