SUBSURFACE STRUCTURE ANALYSIS ON MOUNT SINABUNG, NORTH SUMATERA USING 3-D SEISMIC TOMOGRAPHY FROM JULY 1 – SEPTEMBER 30 2013

• Main Author: Kurniajati, Bagas
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/36398
• Institution: Institut Teknologi Bandung

The Sinabung volcano is located in Karo Regency, North Sumatra with altitude of 2460 m above sea level. Since the sudden eruption in 2010, Sinabung volcano, which is previously a volcano type B, turned into a volcano type A. Variations in the seismic velocity and earthquake hypocenter distribution can be determined using the Local Earthquake Tomography (LET) to well-describe the subsurface structures. We selected 1108 local earthquakes data catalog of CVGHM from July 1 until September 30 2013. Waveform cross-correlation data used as input for hypocenter relocation. Hypocenter relocation with double-difference method is perfomed to obtain more precise hypocenter coordinates. Updates 1-D initial velocity model for P and S wave are used as input LET to invert for 3-D Vp and Vp/Vs structures. The tomography result showed there is contrast of absolute velocity at depth of 2 km, which may be related to the presence of a boundary between sediment layer and igneous body. Low Vp, Vs, and Vp/Vs ratios at depth of 2 km beneath summit, indicate the presence of heat material along with magmatic gas. Low Vp, and Vs with high Vp/Vs ratios at a depth of 2 km in west flank of Sinabung volcano, are probably related to the presence of magma from southwest. High Vp, Vs, and Vp/Vs ratios at depth of about 2-3 km, are probably related to the presence of igneous body. High Vp, and Vs with Vp/Vs ratios are found at the north side of Sinabung volcano indicate the presence of minerals drying zone. Low velocity anomalies at depth of 1 km that cross from the northeast to southwest are probably related to the fracture zone that associated with the presence of lateral strike slip at Sinabung volcano