Abstract

We mapped 63 conduits, ∼2000 dike segments, and 12 sills in the San Rafael subvolcanic field, Utah (United States), where this Pliocene magmatic system is eroded to a depth of ∼0.8 km and is exceptionally well exposed. Although the number of mapped conduits, dikes, and sills might represent minimums, depending on the level of erosion and exposure, mapped dikes are more numerous around the areally extensive sills and interact with sills and conduits in complex ways. We analyze conduit distribution using kernel density methods and compare results with dike and sill distribution. We find that the distribution of conduits matches the major features of dike distribution, including development of clusters and distribution of outliers. These statistical models are then applied to the distributions of volcanoes in several recently active volcanic fields, where intrusion distributions must be inferred from very sparse data, and compared with San Rafael conduit distribution. This comparison supports the use of statistical models in probabilistic hazard assessment for distributed volcanism. Specifically, renewed dike intrusion and potential eruptions in active basaltic systems can be assessed probabilistically from the distribution of older volcanoes in distributed volcanic systems.

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