DETERMINATION OF CRUSTAL STRUCTURE BENEATH NUSA TENGGARA ISLANDS USING AMBIENT SEISMIC NOISE INTERFEROMETRY

• Main Author: Farduwin, Alhada
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43616
• Institution: Institut Teknologi Bandung

Nusa Tenggara islands located in active tectonic in the eastern part of the Sunda arc and has a complex structure influence by Indo-Australian plate beneath the Sunda plate in the southern part and local back arc thrust in the northern part. Meanwhile, in eastern part of Nusa Tenggara has a complex structure caused by collision process. Ambient noise tomography (ANT) is used to delineate the subsurface structure beneath along the eastern Sunda arc islands especially Bali-Nusa Tenggara islands. In this study, ambient seismic noise interferometry was used to obtain Empirical Green's Function (EGF) from Rayleigh waves. EGF was obtained through cross correlation using 30 BMKG stations located in Bali-Nusa Tenggara and its surroundings with a record period between January and December 2016. The result from that interferometry, show that the energyetic seismic noise source was generated or originated from azimuthal range 500-1100 and 2300-2900 which is related to Banda Sea and Indian Ocean. Vs to depth profile inversion using PSO stochastic inversion method perform a good inversion result and same with previous study. The result from inversion using RR-PSO provided that the mean thickness of the crust in the Nusa Tenggara Islands ranging from ~27-30 km, where the thickness of the crust more thin in the northern part and thicker in the southern part especially Timor Island. From the tomography result, the thickness of Timor Island more than 30 km and the Sumba Island has the thickness ranging from ~23-25 km. Low anomaly in the volcanic arc islands due to the presence of fluid or partial melting that rises to the surface and as the result many volcanoes arise in that area. High anomaly in the Timor Island until depth ~7 km was the basement that has been raised as a collision process. Overall, ANT using local BMKG seismic network data can be used to determine seismic structure in Indonesia.