TECTONIC MODEL OF THE EASTERN SUNDA ARC REGION AND ITS IMPLICATION TO ACTIVE FAULT

• Main Author: Anis Prawoto, Adycipta
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/45153
• Institution: Institut Teknologi Bandung

The Eastern Sunda Arc has a complex tectonics setting. Large magnitude scale of earhquakes prove the active faults in the study area. The large earthquakes not only generated from convergence between Indo-Australian Plate against the island arc, but also we need to be understand about the large earthquake that generated by the back arc thrust fault (i.e. Flores Faults and Wetar Faults). The result of this study is the ilustration of tectonic model that can explain about tectonic condition and geometry of back arc thrust fault. Some data used in this study are topographic data, seismological data (relocated earthquake hypocenter and focal mechanism), and seismic reflection profile. Seismotectonics map obtained from analysis topographic and seismological data, while seismic reflection profile used for describing the geometry and deformation of Flores Fault in more detail. Then, the focal mechanisms in the back arc region are classified based on the depth and mechanism of earthquake source, it for calculating the mean vector of fault plane and stress tensor orientation using PBT axis method. The results of three tectonic models explain that the presence of Flores Fault and Wetar Fault influenced by tectonic condition in the front arc region. The early stage of collision between Scott Plateau againts Sumba and the collision of Timor causing the force towards volcanic arc. This situation make the volcanic arc and the back arc region compressed. The orientation of maximum compression stress (????1) from seven zones also support this statement, which the azimuth maximum stress is perpendicular to the convergence boundary, but plunge of maximum stress in each zones are different. It refers to conclusion, horizontal shortening that occurs in the back arc has a different process stage. Decrease of maximum stress plunge to the east, explain horizontal shortening is more significant on the segment of Wetar Fault than Flores Fault, in other words if shortening process influenced by age difference or time formation, then the Wetar Fault was formed earlier/longer than the Flores Fault.