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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 :
Pemahaman kondisi reservoir merupakan salah satu aspek penting dalam aktivitas monitoring proses produksi fluida dalam sistem panas bumi. Langkah awal manajemen reservoir bagi Lapangan Panas Bumi FR yang baru berproduksi sejak tahun 2014 perlu dilakukan. Penelitian ini bertujuan mendelineasi reservoir khususnya fasa uap menggunakan metode tomografi waktu tunda. Penelitian ini menggunakan data seismogram yang diukur selama 95 hari yang direkam oleh 11 stasiun perekaman. Hasil picking waktu tiba mendapatkan 215 kejadian gempa mikro dengan minimal terekam oleh 3 stasiun perekaman. Distribusi hiposenter awal menunjukkan posisi episenter cenderung mengkluster pada sumur produksi akan tetapi dari segi kedalaman hiposenter masih terdapat fix depth pada elevasi 1170 masl, oleh sebab itu masih diperlukan proses relokasi hiposenter. Relokasi hiposenter dilakukan dengan dua metode secara kombinasi yaitu menggunakan metode Joint Hypocenter Determination (JHD) dan metode double difference. Selanjutnya dilakukan proses tomografi waktu tunda menggunakan perangkat lunak simulsp12. Hasil distribusi relokasi hiposenter menunjukkan satu cluster di sekitar sumur produksi utama yaitu sumur B dan C. Sedangkan dari segi kedalaman hiposenter terdistribusi cluster disekitar trajectory sumur produksi B dan C dari elevasi 1000 sampai 0 masl dengan residual waktu tempuh antara 0.2 sampai 0.4 detik. Hasil tomogram menunjukkan bahwa pada elevasi sekitar 2000 sampai 1000 masl diduga sebagai zona batuan yang mengandung air dengan tingkat alterasi yang cukup besar yaitu zona clay cap dengan nilai VP/VS berkisar 1.73. Sedangkan dugaan zona uap berada pada elevasi 1000-500 masl dengan nilai VP/VS berkisar 1.67-1.7 melampar sepanjang Kawah Ciwidey dengan Kawah Putih. Selanjutnya dilakukan rekonstruksi model konseptual sederhana Lapangan Panas Bumi FR Jawa Barat dengan mengintegrasikan antara data utama penelitian yaitu tomografi microearthquake dan distribusi hiposenter yang sudah terelokasi dengan data pendukung berupa line penampang metode MT 2-D, section vertikal geologi berdasarkan data cutting sumur, profiling sumur temperatur serta lokasi sumur ekstraksi untuk memberikan arah fluida.

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Understanding reservoir conditions is one of the important aspects in fluid production monitoring activity in geothermal systems. The initial step of reservoir management in the FR Geothermal Field which has only been producing since 2014 needs to be done. The object of this study to delineate the reservoir elemen especially the vapor phase using the tomography delay time method. This research used seismogram data measured for 95 days recorded by 11 seismometers. Arrivals time picking results get 215 micro earthquake events with a minimum recorded by 3 recording seismometers. The initial hypocenter distribution shows that the position of the epicenter tends to cluster in production wells but in terms of hypocenter depth there still fix depth at 1170 masl, therefore hypocenter relocation is still needed. Hypocenter relocation is done by two methods in combination. The first use Joint Hypocenter Determination (JHD) and second Double difference relocation method. Then the delay time tomography invers is using simulsp12 software. The results of the hypocenter relocation distribution show one cluster around the main production wells that are wells B and C. While in terms of hypocenter depth distributed clusters around the trajectory of production wells B and C from elevations 1000 to 0 masl with a residual travel time of 0.2 to 0.4 seconds. The tomogram results show that at an elevation arround elevation 2000 to 1000 masl it is prediction that the zone containing water with a considerable alteration rate or usually calls of clay cap zone with a value of Vp / Vs ranging from 1.73. While the prediction steam zone is at an elevation of 1000-500 masl with a value of Vp / Vs ranging from 1.67-1.7 on the part between Ciwidey Crater and Putih Crater. The reconstruction of a simple conceptual model of West Java FR Geothermal Field by integrating the main data likes hypocenter distribution that has been relocated and microearthquake tomography with supporting data in the form of cross section MT 2-D method, geological vertical section based on well cutting data, profiling temperature wells and location of extraction wells to provide fluid direction.

Abstrak :
Identifikasi zona permeabel merupakan aspek penting dalam pengembangan dan pemantauan bidang panas bumi. Zona permeabel umumnya dikaitkan dengan kondisi tegangan bawah permukaan dan adanya struktur seperti fraktur di reservoir. Distribusi dan orientasi fraktur menjadi jalur untuk perbanyakan cairan di reservoir panas bumi. Salah satu metode geofisika untuk mendeteksi keberadaan zona permeabel adalah metode gempa mikro. Metode ini merekam respons alami tegangan-regangan batuan. Studi ini membahas distribusi gempa mikro, distribusi intensitas, dan orientasi fraktur. Data yang digunakan adalah data gempa mikro yang direkam oleh seismogram pada periode Januari - April 2018. Penentuan gempa hiposenter awal menggunakan perangkat lunak Hypo71. Hasil distribusi Hypocenter dari perhitungan Hypo71 masih memiliki spatial error dan residual RMS yang tinggi karena model kecepatan belum sesuai dengan kondisi bawah permukaan lapangan. Oleh karena itu, pembaruan model kecepatan dan relokasi hiposenter diperlukan dengan perangkat lunak Joint Hypocenter Determination (JHD) Velest. Distribusi hiposenter yang telah dipindahkan menunjukkan pergeseran posisi hiposenter ke area zona produksi dan beberapa mengikuti tren struktur permukaan. Sedangkan untuk memetakan distribusi intensitas dan orientasi fraktur, analisis Shear Wave Splitting (SWS) digunakan. Fenomena SWS terjadi ketika gelombang S merambat melalui media anisotropi. Gelombang S akan dibagi menjadi dua polarisasi (ɸ) dengan kecepatan yang berbeda, yaitu Sfast yang paralel dan Sslow yang tegak lurus dengan orientasi fraktur. Teknik korelasi rotasi digunakan untuk menentukan parameter SWS, yaitu arah polarisasi (ɸ) dan waktu tunda (dt) gelombang S. Hasil penelitian ini menunjukkan bahwa area tengah WKP memiliki intensitas patah yang tinggi didukung oleh keberadaan sumur dengan produksi uap terbesar di lapangan dan munculnya struktur yang lebih kompleks di permukaan. Sedangkan arah dominan orientasi fraktur dalam penelitian ini relatif paralel mengikuti tren struktur lokal NW-SE dan NE-SW. ......Identification of permeable zones is an important aspect in the development and monitoring of the geothermal field. Permeable zones are generally associated with subsurface stress conditions and the presence of fracture-like structures in the reservoir. The distribution and orientation of the fracture is the pathway for the multiplication of fluids in geothermal reservoirs. One geophysical method for detecting permeable zones is the micro earthquake method. This method records the natural response of stress-strain rocks. This study discusses the micro earthquake distribution, intensity distribution, and fracture orientation. The data used are micro earthquake data recorded by seismograms in the period January - April 2018. Determination of the initial hypocenter earthquake using Hypo71 software. Hypocenter distribution results from the calculation of Hypo71 still have high spatial error and RMS residuals because the velocity model is not in accordance with the subsurface conditions. Therefore, updating the speed model and relocating the hypocenter is needed with Velest Joint Hypocenter Determination (JHD) software. The distribution of the hypocenter that has been moved shows a shift in the position of the hypocenter to the area of ​​the production zone and some follows the surface structure trends. Whereas to map the fracture intensity and orientation distribution, Shear Wave Splitting (SWS) analysis is used. SWS phenomenon occurs when S waves propagate through anisotropic media. S waves will be divided into two polarizations (ɸ) with different speeds, namely Sfast which is parallel and Sslow which is perpendicular to the fracture orientation. Rotational correlation technique is used to determine the SWS parameters, namely the direction of polarization (ɸ) and the time delay (s) of S waves. The results of this study indicate that the central area of ​​the WKP has a high fracture intensity supported by the presence of wells with the largest steam production in the field and the appearance of structures which is more complex on the surface. While the dominant direction of fracture orientation in this study is relatively parallel following the trends of the NW-SE and NE-SW local structures.

Abstrak :
Pulau Jawa merupakan wilayah seismik aktif karena merupakan bagian dari Busur Sunda yang terletak di atas penunjaman antara Lempeng IndoAustralia terhadap Lempeng Eurasia. Khususnya di Jawa Timur, data terbaru maupun catatan sejarah mengatakan bahwa aktivitas gempa di Jawa Timur termasuk sangat aktif. Penelitian ini menggunakan tomografi double-difference untuk mencitrakan struktur kecepatan seismik 3D gelombang P dan S yang berkaitan dengan pola tektonik akibat zona subduksi. Data yang digunakan berasal dari katalog gempa dan katalog waktu tiba gelombang milik BMKG dengan periode perekaman dari 1 Januari 2020 hingga 31 Januari 2023. Terdapat 1.816 dari total 1.831 yang berhasil terelokasi. Proses inversi menunjukkan berkorelasi positif dengan keberadaan Cekungan Jawa Timur Utara berdasarkan seragamnya zona kecepatan rendah di area yang tersusun atas endapan dan batuan sedimen tersebut. Terdapat anomali kecepatan rendah yang diduga disebabkan oleh aktivitas magmatis di sepanjang rangkaian pegunungan berapi Jawa Timur, juga berasosiasi dengan aktifitas sesar lokal yakni Sesar Kendeng. ......Java Island is an active seismic region as it is part of the Sunda Arc, located above the subduction zone between the Indo-Australian Plate and the Eurasian Plate. Specifically in East Java, both recent data and historical records indicate high seismic activity. This study utilizes double-difference tomography to image the 3D seismic velocity structure of P and S waves related to tectonic patterns resulting from subduction zones. The data used is derived from the earthquake catalog and wave arrival time catalog owned by BMKG, covering the recording period from January 1, 2020, to January 31, 2023. Out of a total of 1,831 events, 1,816 were successfully relocated. The inversion process shows a positive correlation with the presence of the North Java Basin, indicated by a consistent low-velocity zone in the area composed of sedimentary deposits and rocks. Low-velocity anomalies are suspected to be caused by magmatic activity along the volcanic mountain range of East Java, also associated with local fault activity, the Kendeng Fault.

Abstrak :
Wilayah Sulawesi Utara mengalami deformasi aktif akibat aktivitas lempenglempeng tektonik di bawah permukaan, sehingga menciptakan zona subduksi serta sesar-sesar aktif. Menjadikan Sulawesi Utara memiliki potensi risiko gempa yang signifikan. Sehingga mengetahui keakuratan hiposenter gempa merupakan langkah awal dalam upaya memahami risiko seismik serta mengimplementasikan tindakan pencegahan yang sesuai. Relokasi hiposenter dilakukan dengan memanfaatkan data katalog arrival time gelombang P dan S dari International Seismological Center (ISC) pada tahun 2012-2022, dengan total 8.058 kejadian. Algoritma relokasi yang digunakan adalah Double Difference yang berfokus pada perbandingan jarak antara 2 hiposenter. Model kecepatan yang digunakan adalah model kecepatan 1D lokal di stasiun SMSI. Hasil pengolahan menunjukkan terdapat 4,456 kejadian yang berhasil terelokasi. Melalui analisis distribusi hiposenter diindikasikan bahwa distribusi kejadian menjadi lebih teratur dan terlihat pola klasterisasinya dibandingkan sebelum direlokasi. Gempa lebih memadat di daerah sekitar Patahan Gorontalo. Distribusi gempa yang tadinya ada di sebelah utara dari Trench Sulawesi Utara cenderung memadat ke arah selatan. melalui uji validasi dengan residual waktu tempuh mendekati 0 yang meningkat. Dengan demikian, metode double-difference diasumsikan mampu memberikan pola kegempaan yang lebih jelas dalam analisis gempa. ......The region of North Sulawesi undergoes active deformation due to the tectonic plate activities beneath its surface. This plate movement creates subduction zones and active faults, making North Sulawesi significantly at risk for earthquakes. Thus, understanding the accuracy of earthquake hypocenters is a fundamental step in comprehending seismic risk and implementing appropriate preventive measures. Hypocenter relocation was carried out using the arrival time catalogue data of P and S waves from the International Seismological Center (ISC) between 2012-2022, totalling 8,058 events. The relocation algorithm used is the Double Difference method, which focuses on comparing the distances between two hypocenters. The velocity model is a local 1D velocity model at the SMSI station. The processing results indicate that 4,456 events were successfully relocated. Analyzing the hypocenter distribution shows that the events’ distribution became tidier and cluster patterns were more evident than before relocation. Earthquakes became denser around the Gorontalo Fault. The distribution of earthquakes, previously north of the North Sulawesi Trench, tends to shift southward, as validated by travel time residuals approaching 0, which increased. Therefore, the double-difference method is assumed to provide a more precise seismic pattern in earthquake analysis.

Abstrak :
Lombok merupakan sebuah daerah di Indonesia yang berbatasan langsung dengan zona subduksi antara lempeng Eurasia dengan lempeng Indo-Australia di bagian selatan. Subduksi ini menimbulkan sesar naik sepanjang utara Lombok hingga Flores yang diketahui sebagai Sesar Flores. Sesar tersebut merupakan sumber dari aktivitas seismik pada daerah Lombok dan sekitarnya. Keberadaan sesar pada suatu lokasi dapat ditentukan dari lokasi hiposenter gempa bumi yang dihasilkan serta dapat ditingkatkan akurasinya dengan data hiposenter yang telah direlokasi. Metode relokasi double difference sering digunakan untuk mengurangi galat akibat ketidaksesuaian waktu tempuh. Namun demikian, galat akibat nilai ketidakpastian hiposenter saat penentuan awal masih tetap mempengaruhi akurasi data. Metode collapsing diterapkan untuk menanggulangi hal tersebut sehingga dapat meningkatkan akurasi penentuan hiposenter gempa bumi. Penerapan metode collapsing terhadap data gempa bumi Lombok menunjukkan kemiringan sesar Flores sebesar 7.25º yang disebabkan oleh dorongan subduksi lempeng Indo-Australia secara horizontal sehingga membentuk decollement serta keberadaan splay fault dengan kemiringan sebesar 20-45º. Analisis kluster gempa bumi terhadap periode gempa menunjukkan indikasi keberadaan microblock Flores dan Sumbawa yang terpisah dari Bali dan sekitarnya.

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Lombok is part of an area in Indonesia which borders with subduction zone between Eurasian plate and Indo-Australian plate at the southern part, causing formation of thrust fault from north of Lombok to Flores, known as Flores Fault. The fault is the source of seismic activity in Lombok Area. Location of faults can be determined by earthquake hypocenters data, its accuracy improved by relocation method. Double difference method is widely used to reduce errors caused by travel time mismatch. However, errors by earthquake location uncertainty during initial determination remain uncorrected. Therefore, collapsing method can be utilized to decrease such errors to increase accuracy of the data. The method was applied to Lombok earthquake data. The result was the determination of structure resembling a decollement with the dip of 7.25º and a splay fault at 20-45º. Cluster analysis plotted by occurence period indicates presence of Flores-Sumbawa microblock.