INTERPRETATION COMPARISON USING MOVING AVERAGE AND SECOND ORDER POLYNOMIAL METHOD OF MERAPIâS SUBSURFACE
The position of Indonesia at the meeting point of three huge plates which are Eurasian plate, Indo-Australia plate, and Pacific plate caused the formation of volcanoes series around it. Merapi Volcano is the most active volcano in Indonesia which surrounded by densely populated settlements with Y...
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| Format: | Final Project |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/42358 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | The position of Indonesia at the meeting point of three huge plates which are
Eurasian plate, Indo-Australia plate, and Pacific plate caused the formation of
volcanoes series around it. Merapi Volcano is the most active volcano in Indonesia
which surrounded by densely populated settlements with Yogyakarta as the closest
city which is only less than 30 km from the summit. These conditions caused Merapi
Volcano as a very hazardous mountain and included into the list of 16 Decade
Volcanoes by The International Association of Volcanology and Chemistry of
Earth’s Interior (IAVCEI). Therefore, research on subsurface structures,
especially the structure of magma sources is important to understand the
characteristics of Merapi Volcano. One of the methods that can be used is the
gravity method which aim to model the structure of the magma source beneath the
surface of Merapi Volcano. The data used in this study is a print complete Bouguer
anomaly map of Merapi Volcano as result of gravity measurement in 2013. The
map was converted into a digital map so that further processing can be done. Then
the regional anomaly and residual anomaly separation process was carried out
using moving average method and 2nd order polynomial method. Forward modeling
in 2.5 D used ModelVision software based on geological information with
background density value of 2.67 g/cc. The modeling results obtained showed a
source of two basaltic andesite magma chambers. Layers of Merapi’s subsurface
from old to young were lava flows of old Merapi, pyroclastic flow and lahar
deposits, pyroclastic fall deposits, young (Post-Somma-Merapi) lava flows, and
recent and mostly historical pyroclastic flow and lahar deposits. Sentolo Formation
was suspected in the southern area. Kukusan Faults as normal fault were found in
the southern and eastern area of the cross section. Differences in the models
obtained from the two methods were the depth of the magma chamber, diameter of
the magma chamber, distribution of layers, depth of the layers, and thickness of the
layers of Merapi’s subsurface. |
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