PEMODELAN STRUKTUR BAWAH PERMUKAAN ZONA SUBDUKSI DAN BUSUR GUNUNGAPI JAWA TIMUR BERDASARKAN ANALISIS DATA GRAVITASI; SUBSURFACE STRUCTURE MODELLING OF EAST JAVA SUBDUCTION ZONE AND VOLCANIC ARC BASED ON GRAVITY DATA ANALYSIS

Setiawan, Muhamad Ragil, Ari Setiawan

2015 | Disertasi | FMIPA

The subduction zone to the south of East Java is a part of a long subduction formed by collision of Indo-Australian and Eurasian plate. The existence of the subduction is interesting to be studied since it also affects the volcanic activity and potential of geohazards in the area. The study of subduction zone and volcano was conducted by modelling the subsurface structure using gravity anomaly with the help of program Grablox and Bloxer. The modelling was conducted on secondary data of free air gravity anomaly, regional anomaly, and local anomaly. The data of secondary gravity anomaly was obtained from Bureau Gravimetrique Internationale (BGI). The modelling construction was performed by inversion technique applying Singular Value Decomposition (SVD) method and Occam optimization. Result of the study indicated there was oceanic crust thinning in average that was from 20 km to 15 km to the north. The thinning was caused by the protuding upper mantle pressuring crush called flexural bulge. The thickness of sedimentary rocks in the back-arc basin was ~4.50 km, and the more it was to the east, the more the value decreased. The existence of magma chamber generally was estimated at depth of 6 km

Kata Kunci : Gravity Anomaly; Subduction Zone and Volcano; Grablox and Bloxer;Gravity Anomaly Modelling