Pemodelan Gaya Berat 3d Daerah Panas Bumi Dolok Marawa Kabupaten Simalungun, Sumatera Utara 3d Gravity Modeling of Dolok Marawa Geothermal Field in Simalungun Regency, North Sumatera

Abstract

Daerah panas bumi Dolok Marawa merupakan salah satu daerah prospek panas bumi di Sumatera bagian utara. Daerah panas bumi tersebut berada pada zona patahan Sumatera dengan manifestasi permukaan berupa sekelompok mata air panas yang memiliki temperatur antara 37o C hingga 65 o C. Serangkaian survei gaya berat telah dilakukan di daerah ini pada tahun 2006 dan 2015. Sebanyak 257 data gaya berat telah diukur dari daerah ini, dengan cakupan luas pengukuran sekitar 16 km x 13 km. Penelitian ini bertujuan untuk mengetahui distribusi densitas batuan melalui pemodelan 3D pada data gaya berat dengan menggunakan perangkat lunak Grablox. Hasil pemodelan memperlihatkan suatu blok berdensitas rendah yang bentuknya berarah baratlaut-tenggara dan berimpit dengan zona patahan. Densitas batuan rendah tersebut bernilai sekitar 2,4 g/cm 3 dan dianggap sebagai batuan rekahan yang mengisi zona patahan. Hasil pemodelan juga memperlihatkan suatu blok berdensitas tinggi di bawah bukit Dolok Bahtopu. Blok densitas tinggi ini diinterpretasikan sebagai suatu tubuh intrusi andesitik dan mungkin bertindaksebagai sumber panas bagi sistem panas bumi Dolok Marawa.

3D inversion modelling of gravity data for identification of subsurface structures in the mud volcano area of Sedati, Sidoarjo

“…Zhao (2011) explains that Singular Value Decomposition inversion is a technique of parsing a mtrix into two matrices. Zhao (2011) also gives an example of SVD inversion, which is to decompose matrix A into matrix U and matrix V, if written mathematically [7], we get an equation like this: A = U S V T (1) where U is a left-hand orthogonal matrix, S is a diagonal matrix, and V is a right-hand orthogonal matrix.…”

“…The gravity method can provide a model of the subsurface structure of the earth based on the distribution of the density values of the constituent rocks [5]. The gravity method can be used because it can delineate the subsurface structure [6] in the form of an indication of the presence of mud which is characterized by low-density contrast with the surrounding rock [7]. Research on mud volcanoes using gravity data has been carried out in Golestan Province, Iran [8] which succeeded in obtaining a gravity data model with a density variation of 2.55 to 2.239 gr/cm 3 .…”

Geometry Analysis of Penang Island Faults Based on Satellite Gravity Data

“…Singular Value Decomposition (SVD) inversion is a matrix factoring technique by decomposing a matrix into two matrices, for example from matrix A to matrices U and V. The equation is expressed mathematically as follows [15]: 𝑨 = 𝑼 𝑺 𝑽 𝑻 (5) Where U is the left orthogonal matrix, S is the diagonal matrix, and V is the right orthogonal matrix. Occam's inversion is an inversion technique that uses the roughness level of a model [16] which is described in the following equation.…”