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Abstrak :
[ABSTRAK
Penentuan zona rekahan reservoar di daerah Geotermal sangat penting untuk keperluan penentuan titik pemboran. Penentuan zona rekahan tersebut dapat dilakukan dengan menerapkan metode geofisika, salah satunya adalah metode microearthquake (MEQ). Metode MEQ dapat memberikan informasi yang berkaitan dengan struktur permeabilitas reservoar, pola pergerakan fluida injeksi, dan batas reservoar pada lapangan Geotermal. Terdapat beberapa metode penting yang dilakukan untuk analisis zona rekahan dari data MEQ, yaitu relokasi menggunakan metode double difference, tensor momen dan tomografi. Dalam hal ini penulis berupaya untuk melakukan penelitian pengembangan software terkait penentuan waktu tiba menggunakan spektrogram. Setelah lokasi hiposenter diperoleh, maka langkah berikutnya adalah melakukan analisis tensor momen dan tomografi. Dari berbagai analisis yang dilakukan tersebut, penentuan zona rekahan di daerah Geotermal dapat dilakukan dengan baik. Diharapkan penelitian ini memberikan hasil yang terbaik sehingga metode yang dilakukan tersebut dapat diterapkan dalam penentuan zona rekahan yang lebih tepat.

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ABSTRACT
Determination of the reservoir fracture zone in Geothermal areas are very important for the purposes of determining the drilling point. Determination of the fracture zone can be performed by applying geophysical methods, one of which is a microearthquake (MEQ) method. MEQ method may provide information relating to the structure of the reservoir permeability, patterns of fluid injection movement, and boundary the field of Geothermal reservoir. There are several important methods to analyze fracture zone performed on the data MEQ, relocation using the double difference method, moment tensor and tomography. In this case the author seeks to conduct research related to the development of software such methods can be used to process and analyze the MEQ data. In this case I do research related to software development related to the timing of arrival using the spectrogram. After the location of the hypocenter is obtained, then the next step is to analyze the moment tensor and tomography. From the various analyzes performed, the determination of the fracture zone in the Geothermal area can be done well. It is expected that this study provides the best results so the methods can applied in the determination of a more precise fracture zone.;Determination of the reservoir fracture zone in Geothermal areas are very important for the purposes of determining the drilling point. Determination of the fracture zone can be performed by applying geophysical methods, one of which is a microearthquake (MEQ) method. MEQ method may provide information relating to the structure of the reservoir permeability, patterns of fluid injection movement, and boundary the field of Geothermal reservoir. There are several important methods to analyze fracture zone performed on the data MEQ, relocation using the double difference method, moment tensor and tomography. In this case the author seeks to conduct research related to the development of software such methods can be used to process and analyze the MEQ data. In this case I do research related to software development related to the timing of arrival using the spectrogram. After the location of the hypocenter is obtained, then the next step is to analyze the moment tensor and tomography. From the various analyzes performed, the determination of the fracture zone in the Geothermal area can be done well. It is expected that this study provides the best results so the methods can applied in the determination of a more precise fracture zone.;Determination of the reservoir fracture zone in Geothermal areas are very important for the purposes of determining the drilling point. Determination of the fracture zone can be performed by applying geophysical methods, one of which is a microearthquake (MEQ) method. MEQ method may provide information relating to the structure of the reservoir permeability, patterns of fluid injection movement, and boundary the field of Geothermal reservoir. There are several important methods to analyze fracture zone performed on the data MEQ, relocation using the double difference method, moment tensor and tomography. In this case the author seeks to conduct research related to the development of software such methods can be used to process and analyze the MEQ data. In this case I do research related to software development related to the timing of arrival using the spectrogram. After the location of the hypocenter is obtained, then the next step is to analyze the moment tensor and tomography. From the various analyzes performed, the determination of the fracture zone in the Geothermal area can be done well. It is expected that this study provides the best results so the methods can applied in the determination of a more precise fracture zone., Determination of the reservoir fracture zone in Geothermal areas are very important for the purposes of determining the drilling point. Determination of the fracture zone can be performed by applying geophysical methods, one of which is a microearthquake (MEQ) method. MEQ method may provide information relating to the structure of the reservoir permeability, patterns of fluid injection movement, and boundary the field of Geothermal reservoir. There are several important methods to analyze fracture zone performed on the data MEQ, relocation using the double difference method, moment tensor and tomography. In this case the author seeks to conduct research related to the development of software such methods can be used to process and analyze the MEQ data. In this case I do research related to software development related to the timing of arrival using the spectrogram. After the location of the hypocenter is obtained, then the next step is to analyze the moment tensor and tomography. From the various analyzes performed, the determination of the fracture zone in the Geothermal area can be done well. It is expected that this study provides the best results so the methods can applied in the determination of a more precise fracture zone.]

Abstrak :
ABSTRAK
Analisis seismik untuk mempelajari proses tektonik, kejadian gempa dan interaksi gempa membutuhkan pengetahuan yang akurat terhadap lokasi hiposenter gempa. Akurasi lokasi hiposenter dipengaruhi oleh beberapa faktor, salah satunya adalah pemahaman terhadap struktur lapisan. Pengaruh dari kekeliruan terhadap struktur kecepatan lapisan dapat dengan efektif diminimalisasi menggunakan metode relokasi double-difference. Metode tersebut bekerja dengan meminimasi nilai residu antara selisih waktu tempuh terukur dan terhitung antara dua gempa yang diasumsikan memiliki lintasan rambat gelombang yang sama dari sumber menuju suatu stasiun. Pada penelitian ini, penulis menggunakan data sintetik yang dibuat dengan variasi model kecepatan dan data riil di suatu daerah dekat struktur patahan. Data tersebut diolah menggunakan program HYPO71 yang mengaplikasikan metode Geiger untuk mendapatkan lokasi awal hiposenter, kemudian direlokasi dengan menggunakan program buatan berbasis MATLAB (Delta-Hypo) dan program HypoDD yang mengaplikasikan metode double-difference. Hasil pengolahan data sintetik memberikan peningkatan akurasi episentral hingga 48% dan kedalaman hingga 42%. Hal ini menunjukkan bahwa metode double-difference berhasil merelokasi hiposenter sehingga diperoleh parameter dengan akurasi yang lebih baik, sekalipun terdapat penyederhanaan pada model kecepatan yang digunakan. Hasil pengolahan data riil menunjukkan adanya kesesuaian lokasi hiposenter dengan struktur geologi dan patahan yang ada di lapangan.

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ABSTRACT
Seismicity analysis for the study of tectonic processes, earthquake recurrence, and earthquake interaction requires precise knowledge of earthquake hypocenter locations. The accuracy of absolute hypocenter locations is controlled by several factors, one of which is knowledge of the crustal structure. The effects of errors in structure can be effectively minimized by using double-difference relocation methods. This method works by minimizing residual between observed and calculated differential travel time between two events which assumed had a similar ray path between the source region and a common station. In this research, the author uses synthetic data which varies in velocity model and real data from a certain region near fault structure. These data were processed using HYPO71 program that applies Geiger method to obtain initial hypocenter locations, and then relocated using artificial MATLAB based program (Delta-Hypo) and HypoDD program that applies double-difference method. The synthetic data processing results gives epicentral accuracy improvement up to 48% and focal-depth up to 42%, which shows that double-difference method can successfully relocate hypocenters so that parameters with better accuration are obtained, although there are simplification in velocity model used. The real data processing results shows that the hypocenter locations is appropriate with existing geological and fault structure in the field.

Abstrak :
ABSTRAK
Lokasi hiposenter gempa mikro (microearthquake) dapat dikaitkan dengan kemunculan zona lemah berupa rekahan maupun patahan. Patahan dan rekahan yang merupakan struktur seismik dapat diidentifikasikan melalui proses delineasi persebaran lokasi gempa. Dalam mendelineasi stuktur seismik diperlukan penentuan lokasi gempa dengan tingkat presisi dan akurasi yang baik. Hal umum dari analisis suatu keakuratan lokasi gempa adalah dengan menghitung ketidakpastian formal berupa kesalahan elips, waktu kejadian gempa, dan ketidaksesuaian kedalaman gempa (error ellipsoid, origin time, dan unreliability of depth). Ketidakpastian tersebut digambarkan dalam bentuk elips yang memberikan perkiraan statistik apakah suatu gempa terlokasi secara presisi yang disebut juga error ellipsoid. Salah satu faktor yang dapat mempengaruhi kesalahan penentuan lokasi gempa yaitu geometri jaringan stasiun pengamatan. Geometri stasiun pengamatan memainkan peran penting dalam membatasi ketidakpastian lokasi gempa. Penggunaan geometri jaringan stasiun pengukuran yang optimal sangat penting dan diperlukan untuk menyediakan data waktu tiba yang terpercaya. Penelitian ini bertujuan untuk mengetahui pengaruh geometri jaringan stasiun terhadap ketidakpastian lokasi gempa dalam mendelineasi struktur. Parameter seperti jumlah stasiun, jarak minimum stasiun, dan kemerataan distribusi stasiun. Berdasarkan penelitian, untuk identifikasi struktur patahan melalui delineasi sebaran gempa, maka diperlukan minimal 14 stasiun untuk memperoleh kesalahan lokasi gempa absolut (optimal) ± 1 km untuk episenter dan ± 2 km untuk kedalaman dengan catatan kualitas pengukuran waktu tiba yang baik. Jarak stasiun yang diperlukan yaitu tidak lebih dari perkiraan kedalaman fokus gempa untuk mendapatkan ketidakpastian yang lebih kecil. Distribusi stasiun yang diperlukan untuk identifikasi struktur dapat dilakukan secara acak atau menyebar untuk mendapat cakupan hiposenter yang baik. Berdasarkan penelitian data sintetik, ukuran mendapatkan volume error ellipsoid yang kurang dari 2 km pada yaitu batas azimuthal gap bernilai kurang dari 150ᵒ.

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ABSTRACT
The hypocenter location of the microearthquake can be associated with the appearance of weak zones in the form of fractures or faults. Faults and fractures which are seismic structures can be identified through the delineation of the hypocenter distribution. In delineating the seismic structure, it is important to determine the hypocenter with a good level of precision and accuracy. The general information about the analysis of the accuracy of the hypocenter or earthquake location is to calculate the formal uncertainties in the form of ellipsoid error, origin time, and unreliability of depth. Error ellipsoid can describe the uncertainty in the form of an ellipse that gives a statistical calculation of whether an earthquake is precisely located or not. One of the factors that can affect the error ellipsoid in determining earthquake location is the geometry of the observation station network. The station network geometry acts as an important role to constrain the uncertainty of earthquake location. The optimal use of station network geometry is very important to provide reliable arrival time data. This study aims to determine the effect of station network geometry on the uncertainty of the earthquake location in delineating the seismic structure. Parameters such as the number of stations, minimum station distance, and station distribution uniformity. Based on the research, to identify fault structures through the delineation of earthquake distribution, it requires a minimum of 14 stations to obtain absolute (optimal) earthquake location errors ± 1 km for epicenter and ± 2 km for depth with a reliable record of the quality of arrival time. The required station distance is less than the estimated depth of the earthquake focus to get smaller uncertainties. The station distribution needed for identification of structures can be arranged randomly or uniformly to get sufficient hypocenter coverage. Based on the research of synthetic data, it gets a volume of ellipsoid error which is less than 2 km in that the azimuthal gap limit is worth less than 150ᵒ.

Abstrak :
Permeabilitas batuan merupakan parameter penting dalam meningkatkan drilling success ratio dan monitoring reservoir geotermal. Keberadaannya dikontrol oleh fracture akibat stress. Salah satu metode untuk menentukan keberadaan zona permeabel yang dikontrol oleh rekahan atau patahan adalah MEQ microearthquake . Identifikasi dan analisis karakteristik fracture dapat digunakan untuk mengoptimalkan produktivitas. Data gempa mikro tidak hanya memetakan sebaran zona permeabel berdasarkan sebaran hiposenternya, tetapi juga mampu mengkarakterisasi zona fracture berdasarkan analisis mekanisme fokal dan momen tensor. Dari data MEQ lapangan 'X' dengan memanfaatkan waveform lokal tiga komponen telah dilakukan inversi momen tensor. Hasil penelitian menunjukkan bahwa sebaran fracture yang mengontrol permeabilitas memiliki dominasi arah orientasi strike yakni NW-SE dan NE-SW. Hasil analisis momen tensor menunjukkan pada lapangan bagian Utara di elevasi sekitar 1 km bsl ke atas didominasi komponen implosif, berkaitan dengan pergerakan batuan secara konvergen yang dapat berdampak pada potensi penurunan permeabilitas batuan reservoir. Lapangan bagian Utara di elevasi sekitar 1 km bsl ke bawah menunjukkan komponen-komponen eksplosif, berkaitan dengan pergerakan batuan secara divergen yang mengindikasikan distribusi permeabilitas di lapangan Utara secara keseluruhan tergolong baik. Namun tetap ada potensi dan indikasi penurunan permeabilitas karena jika pergerakan konvergen hasil komponen implosif terus terjadi akibat ekstraksi massa fluida dan tidak diimbangi dengan suplai fluida ke reservoir, maka akan berpengaruh pada sifat fisik reservoir, termasuk penurunan permeabilitas. Selain itu, hasil penelitian ini juga menunjukkan bahwa permeabilitas di zona Selatan cukup besar. ...... Rock permeability is an important parameter in improving drilling success ratio and monitoring of geothermal reservoir. Its existence is controlled by fracture due to stress. Identification and analysis of fracture characteristics can be used to optimize the productivity. MEQ microearthquake is a method that can be used to determine the existing of permeable zones controlled by fractures or faults. MEQ data not only map the permeable zone distribution based on its hypocenter, but also characterize the fracture zones based on analysis of focal mechanism and moment tensor. Moment tensor inversion has done using MEQ data by utilizing three components of local waveform. The results of this study indicate that the distribution of fractures that control permeability has dominant strike orientation direction ie NW SE and NE SW. The results of moment tensor analysis show in the northern field at elevation of about 1 km bsl upward is dominated by implosive components, related to convergent rock movement which can impact on potential decrease of permeability of reservoir rock. The northern field at elevation of about 1 km bsl down show explosive components, related to diverging rock movement which indicates the distribution of permeability in the North field as a whole is quite good. However, there are potential and indication of a decrease in permeability because if convergent motion continues to occur due to fluid mass extraction and is not balanced with fluid supply to the reservoir, it will affect the physical properties of the reservoir, including the decrease in permeability. In addition, the results of this study also indicate that permeability in the South zone is considerable.