EARTHSCOPE AS MOTIVATION FOR INTEGRATIVE TECTONIC STUDIES: AN EXAMPLE FROM THE EVOLUTION OF THE NORTHERN CALIFORNIA PLATE BOUNDARY REGION

The Earthscope initiative provides an opportunity for a greatly improved suite of observations on processes related to active lithospheric tectonics. Although Earthscope per se is simply an instrumentation/observation initiative, the science that it can motivate needs the explicit inclusion of geologic observation, tectonic modeling, and laboratory experiments for maximum effectiveness. As an example of how the combination of Earthscope-like geophysical observations can be coupled with geologic field observations, constraints from laboratory data, and coupled numerical modeling, we present results from our current investigations along the plate boundary in Northern California. As a result of Mendocino Triple junction migration there is a dramatic change in the evolution of the North American lithosphere in its wake. Not only does the San Andreas Fault system develop in its wake, but also the crust of North America is substantially modified from both tectonic thickening/thinning and magmatism. Although Earthscope related programs will dramatically improve the resolution, current observations allow us to develop substantially improved models of the tectonic evolution of the region. For example we can explicitly couple information from geochemical analyses of the volcanic rocks in the region with seismological constraints (from seismic anisotropy) to place constraints on both source regions of the Coast Range Volcanics and the patterns of mantle flow into the developing MTJ slab window. Similarly we exploit the combination of geodetic, geomorphic, and seismological constraints to investigate the links between crustal evolution in the wake of the triple junction and the development and evolution of the river systems and surface processes in the northern California Coast Ranges. In this region of active tectonics and plate boundary evolution it is only with the explicit combination of Earthscope-like geophysical observation, geologic data, and coupled numerical modeling that we have been able to develop constrains models of plate boundary evolution. In a similar fashion the success of Earthscope as a catalyst for advances in research in lithospheric tectonics requires a similar collaborative approach.