Ductility directly related to crustal fluids may play a very important role in the distribution of crustal seismicity and large scale crustal deformation in the Puget Sound region. The strong correlation between crustal fluids and electrical resistivity makes for specific, testable predictions about the resistivity structure. The most fundamental are that there will be a sharp resistivity decrease at the top of the seismically active crust if it coincides with the base of the volcanics and another at the bottom of the seismically active lower crust if it coincides with a brittle- ductile transition associated with trapping of water by a metamorphic boundary. A combined Magnetotelluric (MT) and Magnetic variation (MV) array study capable of making the required tests will be carried out.
