[S21-P] Poster

[S21-P-14] Three-Dimensional Seismic Velocity Models of P and S Waves Beneath Western Part of Java, Indonesia from Double-difference Tomography

^○Shindy Rosalia¹, Sri Widiyantoro², Andri Dian Nugraha² (1.Geophysical Engineering Study Program, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia, 2.Global Geophysical Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia)

Western part of Java is located in active subduction zone where the Indo-Australian plate is subducted under the Eurasian plate. In this study, double-difference tomography has been applied to obtain 3D velocity structures of P and S waves beneath the western part of Java. We have used regional earthquake waveform data taken from the Meteorological, Climatological, Geophysical Agency (BMKG) of Indonesia network from south of Sumatra to central Java. We have re-picked P and S arrival times from about 800 events in the period from April 2009 to December 2015. We have also used additional arrival time data of BMKG catalog for period from January to July 2016. We have selected events which have azimuthal gap < 210 degrees, magnitude > 3, and number of phases > 8. Double-difference tomographic imaging using these data gives a clear velocity structure beneath the western part of Java, especially in the volcanic arc area, i.e. below Mount Anak Krakatau, Mount Salak complex and southern mountains complex in West Java. We observed low velocity anomalies of P and S waves and high Vp/Vs under the volcanoes at depth interval of 80-100 km that may indicate hot partial melting ascending from subducted slab beneath the volcanic arc.