Crustal Deformation caused by magma migration in the northern Izu Islands, Japan

Intense crustal activity including earthquake swarms, eruptions, and a caldera formation in the northern Izu Islands started on June 26, 2000, accompanied with large crustal deformation. Permanent CPS data reveals the spatial pattern and time evolution of ground deformation. The observations reveal shrinking and subsidence of Miyakejima and extension between Kouzushima and Niijima. We constructed a source model to explain the observed displacements during the period between June 26 and the end of August. The model consists of a deflation source (0.12km(3)) beneath Miyakejima, tensile faults (1.04km(3)) located between Miyakejima and Kouzushima, and several shear faults. Mass balance considerations suggest that a large amount of magma migrated 30km from Miyakejima toward Kouzushima.