3-D Inversion of Gravity Data Using Iterative Calculation for Subsurface Modeling of Mt. Pandan, East Java, Indonesia
Abstract
Mount Pandan is one of the volcanoes located in East Java.There was an earthquake with magnitude 4.2 on
Thursday, June 25, 2015, at 10.35 pm located in the area of Mount Pandan. The earthquake indicates the active tectonic of Mount Pandan. In addition, Mount Pandan is one of eleven geothermal prospects in East Java. Thus, it is interesting to do a study related to the geological condition of Mount Pandan. So far, most studies have discussed the related surface geology of Mount Pandan. This study aims to provide information related to the subsurface condition of Mount Pandan based on gravity data. In this research, gravity data inversion modeling technique is used to image the subsurface condition of Mount Pandan. The inversion technique used is non linear inversion with iterative calculation method. In this modeling scheme, the model to be determined
is a layer boundary depth model of two layers of rock based on gravity anomaly data. In each layer the rock is assumed to be composed of a set of rectangular prisms with a certain dimension. A collection of prisms representing the rock layers is then computed by the model response and evaluated by comparing it to the observed data. From this evaluation, a modication of the length of the prism is made so that
the boundary layer model will change. The process of evalu ation and modication of the model is done iteratively until it reaches the number of predened iterations. The result obtained from this gravity inversion modeling is a model of the subsurface boundary of Mount Pandan. The subsurface model obtained is the existence of a formation resembling a rock intrusion, in this case interpreted as an andesitic rock
that intrudes overlying rock layers. This intrusive formation lies at the peak of Mount Pandan and is continuously to the north, with the undisturbed intrusion located around the summit of Mount Pandan.
References
bridge.
Chai, T. dan Draxler, R.R. (2014): Root mean square error (RMSE) or mean absolute error (MAE)?- Arguments
against avoiding RMSE in the literature, Geoscientific Model Development, 7, 1247 { 1250.
Lunt, P., R. Netherwood, dan O.F. Human (1998): Guide book of IPA field trip to Central Java. Indonesian
Petroleum Association, Jakarta,. 65pp.
Nugraha, A. D., Shiddiqi, H. A., dan Widiyantoro, S. (2016): Unexpected earthquake of June 25th, 2015 in Madiun, East Java, AIP Conference Proceeding, 1730, 020001.
Plouff, D. (1976): Gravity and magnetic fields of polygonal prisms and application to magnetic terrain corrections, Geophysics, 41, 727 { 741.
Pringgoprawiro, H. dan Sukido (1992): Peta Geologi lembar Bojonegoro, Jawa Timur, Pusat Penelitian dan Pengembangan Geologi.
Santoso, D., Wahyudi, E. J., Alawiyah, S., Nugraha, A. D., Widiyantoro, S., Kadir, W. G. A., Supendi, P., Wiyono, S.,
dan Zulfakriza. (2017): Subsurface structure interpretation beneath of Mt. Pandan based on gravity data, IOP Conf. Series: Earth and Environmental Science, 62, 012038.
Setijadji, L. (2010): Segmented volcanic arc and its association with geothermal elds in Java Island, Indonesia,
Proceeding World Geothermal Congress.
Smyth, H., Hall, R., Nichols, G. J. (2005): East Java: Cenozoic Basins, volcanoes, and ancient basement, Indonesian
Petroleum Association Annual Convention , 30, 251 { 266.
Tan, T.S., Phoon, K.K., Hight, D.W., dan Lerouiel, S. (2003): Characterization and engineering properties of nat-
ural soils, A.A. Balkema Publishers, Tokyo.
Telford, W.M., Geldart, L.P., dan Sheri, R.E. (1990): Applied geophysics second edition, Cambridge University
Press 1990, Cambridge.
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