Indonesia is one of the most interesting targets for seismic tomographic studies due to its tectonic complexity. The subduction zone was formed when the Indian oceanic plate was subducted beneath the Eurasian continental plate. This activity caused the formation of volcanoes along the Sunda Arc, including the area of East Java. In this study, we aim to identify the influence of volcanic activities which extends from the west to the east of East Java. We used the data of 1,383 earthquakes, recorded by the 22 stations of the Indonesia Tsunami Early Warning System (InaTEWS) seismic network. We relocated the earthquakes and conducted a tomographic study using SIMULPS12. We then explored the anomalies of P- and S-wave velocities and Vp/Vs ratio. The low-velocity zone was observed in the volcanic area related to the partial melting zone or magma chamber with high Vp/Vs. This zone is observed at the depth range from 27 to 155 km and is correlated with the slab of Java subduction zone. We assume that the plumbing system of volcanoes is interlinked. If it is true, this can be helpful to carry out further detailed studies regarding the continuity of the plumbing system and the volcanic arc.

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