IDENTIFIKASI ORIENTASI REKAHAN MIKRO AREA PANAS BUMI MONTE AMIATA BERDASARKAN ANALISIS STUDI SHEAR WAVE SPLITTING

Irfan - Hanif, Ahmad Zaenudin, Nandi Haerudin, Rahmat C Wibowo

Abstract

Shear Wave Splitting is an application of seismic wave to analyse the anisotropy level of a certain medium. Generally, shear wave propagation through a rock formation will be polarized (φ) into two parts especially when the medium structures are different, such as fracture. The polarized shear wave which is perpendicular to fracture will propagate slower than the wave that propagates parallel to the fracture. The delay time (δt) of both wave is proportional with the fracture intensity along the wave propagation from the source to the station. The description regarding fracture orientation can be obtained by analysing both Shear Wave Splitting parameters (φ and δt), and this information is adequately important in geothermal exploration or exploitation phase at Mt. Amiata. Based on the result of this research, the micro earthquake source is focused on the east to the south area and spread along 3 earthquake stations. The existence of micro earthquake source is mainly focused at the depth of 1 to 4 km. In addition, the polarization direction of each earthquake station at the geological map shows a dominant fracture orientation consistently at NW-SE. All of the three stations also show that the polarization direction is integrated to the local fault existence in the subsurface. Furthermore, the research shows that the high intensity fracture distribution occurred at MCIV station area in the southern part of research location. Meanwhile, the low intensity fracture distribution occurred at ARCI and SACS station area in the western and the eastern part of research location. The high value of fracture intensity accompanied by the high amount of structure intensity, strengthen the prediction of the high anisotropy existence which potentially tends to the high permeability presence at the area.

Keywords: shear wave splitting, anisotropy, fracture, geothermal, polarization direction, fracture intensity.

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References

Abdullah, A. 2008. Ensiklopedi Seismik Online. E-Book Ensiklopediseismik. Indonesia.

Amatullah, B.A. 2015. Identifikasi Potensi Fracture Permeability Dengan Metode Shear Wave Splitting (SWS) Pada Lapangan Panas Bumi Wayang Windu. Intitut Teknologi Bandung. Tesis.

Anissofira, A. 2013. Penentuan Struktur Patahan di Lapangan Panasbumi X Dengan Menggunakan Metode Relokasi Relatif Kasus Gempa Mikro. Universitas Pendidikan Indonesia. Skripsi.

Barelli, A., Ceccarelli, A., Dini, I., Fiordelisi, A., Giorgi, N., Lovari, F., dan Romagnoli, P. 2010. A Riview of the Mt. Amiata Geothermal System (Italy). Proceedings World Geothermal Congress 2010. Pp 1-6.

Batini, F., Brogi, A., Lazzarotto, A., Liotta, D., dan Pandeli, E. 2003. Geological features of Larderello-Travale and Mt Amiata geothermal areas (southern Tuscany Italy). Episodes 26, 239-244.

Dini, I., Ceccarelli, A., Brogi, A., Giorgi, N., Galleni, P., dan Rossi, L. 2010. Geological Evolution of the Base Mt. Amiata Volcanic Complex (Tuscany, Italy). Proceedings World Geothermal Congress 2010. Pp 1-9.

Fulignati, P., Marianelli, P., Sbrana, A., dan Ciani, V. 2014. 3D Geothermal Modelling of the Mount Amiata Hydrothermal System in Italy. Energies Journal. VOL. 7, 7434-7453.

Holland. 2002. Microearthquake Study of the Salton Sea Geothermal Field, California: Evidence of Stress Triggering. The University of Texas. USA.

Kissling, E. 1995. Program VELEST USER’S GUIDE Short Introduction. Institute of Geophysics. ETH Zuerich.

Nishi, K. 2005. Hypocenter Calculation Software GAD (Geiger’s method with Adaptive Damping). GAD Manual Guide.

Olive, J.A. 2014. An Eigenvalue-Method for Shear Wave Splitting Analysis. MIT/WHOI Joint Program in Oceanography. USA.

Rozzano, F., dan Cei, M. 2015. Geothermal Power Generation in Italy 2010-2014 Update Report. Proceedings World Geothermal Congress 2015. Pp 1-10.

Stich, D., dan Morelli, A. 2007. Reflection of Seismic Surface Waves at the Northern Apennines. Earth planet. Sci. Lett. 259, 149-158.

Telford, W.M., Geldart, L.P., dan Sheriff, R.E. 1990. Applied Geophysics Second Edition. Cambridge University. USA.

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