Distribution of seismic wave velocity beneath Sunda-Banda arc transition zone using Local Earthquake Tomography Free

We studied the 3D seismic tomography modeling for the internal structure of the Earth beneath the Sunda-Banda arc transition zone at coordinates 114 to 125 E and 13 to 4 S with 25 recording stations and tectonic earthquakes as the source of the rays with 7,279 P data and 1,168 S data. The data processing methodology consisted of determination of source location in 3D using ray tracing algorithm and Local Earthquake Tomography Inversion of Lotos-12. The modeling has three models such as: Anomaly velocity modeling, Absolute velocity modeling, Vp/Vs ratio modeling. The results obtained velocity value of P increase from 5.4 km/s to 7.14 km/s of the upper crust and decrease in the eastern part of Sumbawa Island and the western part of Flores Island at 40 km depth. Whereas, the velocity value of S from 2.5 km/s to 4.2 km/s and the coverage data of Vs cannot be found at the depth above 40 km. The results of ratio Vp/Vs has a high value at the depth from 0 to 40 km. In 3D modeling of tomography in the same location, negative anomalies were obtained in the eastern part of Sumbawa Island and the western part of Flores Island. These results are indicative of active volcanic activity under Sumbawa Island and Flores Island as part of the active magmatic arc of the Sunda-Banda region.