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Abstract:
Recent research points to complex, multi-layered, transcrustal magmatic systems beneath volcanoes. But constraints on depths of magma storage in the mid-to-deep crust beneath volcanoes remain an enigmatic target. At volcanic arcs, magmatic processes at these depths are a critical link between the input from the slab and mantle wedge, the emplacement processes that build and alter arc crust, and the shallow crustal reservoirs that drive eruptions. Magmatic storage depths and pathways may be governed by a variety of properties, including volatile content, crustal stress regime, prexisting structures, and more. To better understand how these variables may impact arc volcano processes, we must employ techniques that allow us to characterize magma storage depths at volcanoes globally. Here, we investigate receiver functions as a technique to provide systematic, first-order constraints on magma storage depths in the mid-to-deep crust using data from the Alaska-Aleutian island arc as a case study. Receiver functions are sensitive to abrupt seismic velocity boundaries, and have detected low velocity zones in the crust interpreted as magmatic-mush systems at Akutan and Cleveland, two Alaska-Aleutian arc volcanoes. They do not rely on the presence of local seismicity, do not require a wide-aperature array to image the whole crust, and can be analyzed at volcanoes with relatively few (< 4) local instruments. We present results of the application of this technique across the Alaska-Aleutian arc, and examine along-arc trends in receiver function properties.
