The Colima Deep Seismic Experiment: Imaging the Magmatic Root of Colima Volcano

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ABSTRACTMost of the world's explosive volcanism occurs at widely-spaced volcanic centersalong convergent margins. Basaltic magmas from the subduction wedge arechanneled to volcanoes separated by tens or hundreds of kilometers and evolveinto silica-rich compositions associated with dome growth, pyroclastic flowsand explosive eruptions. Decades of geochemical research have outlined a suiteof processes which control the chemical and spatial evolution of thesevolcanoes. These ideas, which rely heavily on processes in the lowermost crust,have evolved with limited input from geophysics because the deep crust has beendifficult to probe with seismics, gravity, and/or electromagnetics. The ColimaDeep Seismic Experiment is one of the first to target the deep crustalprocesses which create discrete volcanoes and ultimately control eruptivebehavior. In conjunction with the Observatorio Vulcanologico of ColimaUniversity in Mexico, the PI will install and maintain a seismic array for 18months in the vicinity of Colima Volcano. The Observatorio is responsible formonitoring Colima Volcano, which is in the midst of an on-going eruption cycle,and seismicity throughout the state of Colima which has had two earthquakesgreater than magnitude 7.5 in the last ten years. This project will beco-deployed with the arc-scale network of Grand and Ni (EAR #0335782) which isserendipitously centered on Colima. This array of intermediate-band instrumentswill be wider than a typical volcano monitoring array and is designed tooptimize seismic tomography and receiver functions of the deep crust.Teleseismic data, together with seismicity in the local crust and subductingslab, will be used to map the temperature and melt conditions beneath ColimaVolcano. The results will be interpreted in the context of existing geochemicalmodels for the Colima complex to address two primary questions. (i) Is thelocation and longevity of an arc volcano governed principally by diapirism inthe mantle wedge or by deep crustal conditions and Moho topography? (ii) Whatare the relative roles of magma ponding at the base of the crust and magmastorage in the lower crust in controlling the evolution of subduction basaltsinto more silicic arc volcanics? These questions, though ideally suited toColima, have implications at all arc volcanoes. This project is co-sponsored bythe Americas Program in the International Division.