Testing Models of Magma Movement along the East Pacific Rise Using Combined Geoditic and Numerical Experiments

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Abstract (0426575) - CormierThis is a five-year program that will deploy of an array of 20 pressure sensors for four years to monitor magma injection at the NSF-funded RIDGE2000 integrated study site at the East Pacific Rise (9'-10'N). Pressure sensors can successfully detect small (cm) to large (m) vertical motions on mid-ocean ridges. They are also relatively inexpensive and can record data for long periods of time without service. In support of the field program, two modeling efforts will be carried out. The first will interpret measured vertical seafloor displacements that will incorporate the pressure sensor data from the field site. Numerical models of coupled dike intrusion and sill emptying will be developed that include algorithms that take into account the rheological structure of the seafloor at the study site. The second set of models will examine the feasibility of using repeat microbathymetric surveys to constrain surface deformation patterns across a section of a plate boundary. Scientific objectives include discrimination between the two competing models of magma delivery along fast-spreading mid-ocean ridges, the first being where melt is supplied nearly vertically along the ridge axis and the second being where melt is provided at ridge segment centers and propagates toward the segment ends. In the first case, uniform vertical deflections of the pressure sensor network would be expected along the part of a segment cut by a dike, and in the second, pressure sensors would detect significant subsidence near the segment center. Motivation for this study comes from the fact that earthquakes and volcanoes are concentrated on active tectonic plate boundaries, however, nearly 80% of these boundaries occur under the sea and therefore processes occurring there cannot be directly observed. This project, being carried out by researchers at the Woods Hole Institution of Oceanography, will detect, characterize, monitor, and model magma injection episodes along a plate boundary marked by rapid and repeated magma injection events and spreading of the seafloor. Broader impacts of this work include development of a novel magma injection seafloor monitoring system and accompanying modeling tools which have the potential for application to other plate boundaries, student education and training, and making information on the project available to the public and K-12 in a meaningful way through collaboration with the RIDGE2000 outreach program. Development of the bathymetric survey tools also supports the emerging field of marine geodesy.