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"ABSTRAKAnalisis seismik untuk mempelajari proses tektonik, kejadian gempa dan interaksigempa membutuhkan pengetahuan yang akurat terhadap lokasi hiposenter gempa.Akurasi lokasi hiposenter dipengaruhi oleh beberapa faktor, salah satunya adalahpemahaman terhadap struktur lapisan. Pengaruh dari kekeliruan terhadap strukturkecepatan lapisan dapat dengan efektif diminimalisasi menggunakan metoderelokasi double-difference. Metode tersebut bekerja dengan meminimasi nilairesidu antara selisih waktu tempuh terukur dan terhitung antara dua gempa yangdiasumsikan memiliki lintasan rambat gelombang yang sama dari sumber menujusuatu stasiun. Pada penelitian ini, penulis menggunakan data sintetik yang dibuatdengan variasi model kecepatan dan data riil di suatu daerah dekat struktur patahan.Data tersebut diolah menggunakan program HYPO71 yang mengaplikasikanmetode Geiger untuk mendapatkan lokasi awal hiposenter, kemudian direlokasidengan menggunakan program buatan berbasis MATLAB (Delta-Hypo) danprogram HypoDD yang mengaplikasikan metode double-difference. Hasilpengolahan data sintetik memberikan peningkatan akurasi episentral hingga 48%dan kedalaman hingga 42%. Hal ini menunjukkan bahwa metode double-differenceberhasil merelokasi hiposenter sehingga diperoleh parameter dengan akurasi yanglebih baik, sekalipun terdapat penyederhanaan pada model kecepatan yangdigunakan. Hasil pengolahan data riil menunjukkan adanya kesesuaian lokasihiposenter dengan struktur geologi dan patahan yang ada di lapangan.

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ABSTRACTSeismicity analysis for the study of tectonic processes, earthquake recurrence, andearthquake interaction requires precise knowledge of earthquake hypocenterlocations. The accuracy of absolute hypocenter locations is controlled by severalfactors, one of which is knowledge of the crustal structure. The effects of errors instructure can be effectively minimized by using double-difference relocationmethods. This method works by minimizing residual between observed andcalculated differential travel time between two events which assumed had a similarray path between the source region and a common station. In this research, theauthor uses synthetic data which varies in velocity model and real data from acertain region near fault structure. These data were processed using HYPO71program that applies Geiger method to obtain initial hypocenter locations, and thenrelocated using artificial MATLAB based program (Delta-Hypo) and HypoDDprogram that applies double-difference method. The synthetic data processingresults gives epicentral accuracy improvement up to 48% and focal-depth up to42%, which shows that double-difference method can successfully relocatehypocenters so that parameters with better accuration are obtained, although thereare simplification in velocity model used. The real data processing results showsthat the hypocenter locations is appropriate with existing geological and faultstructure in the field."

"[ABSTRAKPenentuan 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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ABSTRACTDetermination 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.]"

"ABSTRAKLokasi 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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ABSTRACTThe 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."

"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.

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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. "

"Metode Magnetotellurik (MT) adalah metode elektromagnetik pasif dengan Tujuannya adalah untuk menentukan nilai resistivitas bawah permukaan. resistensi yang lebih rendah Permukaan digambarkan melalui proses inversi data MT. Dalam penelitian ini menggunakan data sintetik dan data pengukuran menggunakan . metode MT. Tahapan dalam penelitian ini adalah membuat program inversi menggunakan Algoritma capung untuk meminimalkan kesalahan antara data resistivitas semu dariperhitungan algoritma dengan data pengukuran di lapangan, validasi menggunakan data sintetik, dan validasi data pengukuran di lapangan. Hasil penelitian Ini adalah analisis parameter lapisan bawah permukaan, dan akurasi perhitungan Algoritma Dragonfy dengan kesalahan maksimum kurang dari 5.

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The Magnetotelluric (MT) method is a passive electromagnetic method with the aim of determining the value of the subsurface resistivity. lower resistance The surface is depicted through the MT data inversion process. In this study using synthetic data and measurement data using . MT method. The stage in this research is to create an inversion program using the dragonfly algorithm to minimize errors between the apparent resistivity data from algorithm calculation with measurement data in the field, validation using synthetic data, and validation of measurement data in the field. The results of this study are the analysis of the parameters of the subsurface layer, and the accuracy of the Dragonfy Algorithm calculation with a maximum error of less than 5."

"ABSTRAKPemodelan seismik adalah suatu teknik yang digunakan untuk mensimulasikan pergerakan gelombang seismik didalam bumi. Tujuan pemodelan adalah didapatkanya asumsi keadaan struktur bawah tanah dan sebagai salah satu cara dalam mendesain survey lapangan yang sebenarnya. Pemodelan seismik dibuat dengan program matlab yang mengkombinasikan fungsi finite difference dengan general user interface (gui). Keakuratan Metode ini sangat dipengaruhi oleh interval grid yang digunakan, orde, dan geometri dari model geologi yang dibuat. Selain itu, data hasil perekaman seismik sangat dipengaruhi parameter filter, panjang perekaman, clip level, dan Metode akuisisi yang digunakan. Pemilihan parameter yang tepat, akan menghasilkan respon sinyal seismik yang lebih jelas.

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ABSTRACTSeismic modelling is a technique that use to simulating wave propagation in the earth. The purposes are to predict/assumed the structure of subsurface and also to design of seismic survey. The seismic modelling program created by matlab programming that combine finite difference function and general user interface (GUI). The accuracy of its method influenced by grid interval that used, order of finite difference, and geometry from the artificial geological model. Besides that, seismic data record influenced by filtering, duration of record data, clip level and acquisition method. The right parameter option will produce respond of seismic signal clearly."

"Kabupaten Lebak yang terletak di provinsi Banten merupakan daerah yang masih mengalami aktivitas geologi akibat pergerakan dua lempeng tektonik. Kejadian-kejadian gempabumi di daerah ini merupakan manifestasi dari keadaan geologi tersebut. Sangat penting untuk memiliki pemahaman yang lebih mengenai keberadaan struktur di bawah permukaan untuk kewaspadaan terhadap bencana gempabumi dan meningkatkan usaha mitigasi di Indonesia. Penelitian ini menggunakan metode tomografi seismik waktu tempuh double-difference sebagai metode untuk menghasilkan citra di bawah permukaan provinsi Banten, khususnya Kabupaten Lebak, dan sekitarnya. Inversi yang dilakukan menggunakan algoritma TomoDD untuk mencitrakan model kecepatan seismik dengan variasi vertikal dan horizontal dari Provinsi Banten dan dari Jawa Barat. Data yang digunakan merupakan data rekaman 290 kejadian gempabumi yang memiliki total 2.895 fase berupa 2.072 fase gelombang P dan 823 fase gelombang S. Hasil akhir penelitian ini berupa beberapa citra yang diantaranya menunjukkan adanya sesar lokal serta fitur geologi lain seperti Sesar Cimandiri dan zona magmatik.

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Lebak Regency, located in Banten province, is an area that is still experiencing geological activity due to the movement of two tectonic plates. Earthquake events in this area are manifestations of these geological conditions. It is important to have a deeper understanding of the existence of subsurface structures for alertness to earthquake disasters and to improve mitigation efforts in Indonesia. This study used the double-difference travel time seismic tomography method as a method to produce images below the surface of Banten, especially Lebak Regency, and its vicinity. Inversions were performed using the TomoDD algorithm to image seismic speed models with vertical and horizontal variations from Banten Province and from West Java. The data used are record data of 290 earthquake events which have a total of 2,895 phases in the form of 2,072 P-wave phases and 823 S-wave phases. The final results of this study are in the form of several images which shows the existence of local faults and also another geological features such as Cimandiri Fault and magmatic zone."

"Keberadaan noise pada data magnetotellurik dapat membiaskan hasil interpretasi. Noise ini dapat eliminasi dibutuhkan remote station yang jauh dar lokasi pengukuran dan bebas dari interferensi. Remote station diasumsikan bahwa terbebas dari noise, sehingga data dari remote station dapat digunakan untuk mereduksi noise pada stasiun pengukuran. Akan tetapi penambahan remote station ini akan meningkatkan biaya operasional eksplorasi dan juga akan membutuhkan banyak waktu serta sulit untuk mencari lokasi yang terbebas dari noise, terutama pada eksporasi geothermal dikarenakan area di Indonesia yang biasanya memiliki medan dan akses sulit dilalui. Oleh karena itu, diperlukan teknologi yang dapat mengreduksi noise pada data magnetotellurik dan meningkatkan kualitas data sehingga dapat mengurangi biaya dan waktu dalam eksplorasi. Melalui metode continuous wavelet transform, data magnetotellurik yang terkontaminasi noise dapat direduksi tanpa ada bantuan remote station dan akan menyebabkan eksplorasi geothermal menjadi lebih efisien. Metode continuous wavelet transform mengolah data magnetotelurik berupa time series domain yang masih belum difilter dan mengubah data time series domain tersebut ke dalam time-frequency domain. Pengubahan menjadi time-frequency menggunakan metode continuous wqavelet transform untuk dianalisis keberadaan noisenya pada frekuensi dan waktu kemunculan noise yang kemudian dihilangkan. Data yang telah dihilangkan akan dapat diolah menjadi apparent resistivity dan fase vs frekuensi. Hasil filter yang telah dilakukan dibandingkan dengan pengolahan software komersil. Dimana filter berhasil menghilangkan keberadaan noise transient yang muncul dengan kisaran frekuensi 30-400 Hz dan kemunculan selama 0.2-0.4 detik. Sehingga filter ini dapt menjadi alternatif lain dalam penghilangan noise pada data magnetotelurik.

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The presence of noise in magnetotelluric data can produce a bias in its interpretation. To eliminate this noise, a remote station that is far from interference is needed. Assuming that the remote station is almost free from noise, the data from remote station can be used to reduce the noise from measurement station. However, adding an additional station means there will be an increase in exploration cost. Also, adding a remote station itself can be challenging and time-wasting since finding an area that is free from interference is quite hard to do, especially for geothermal exploration area in Indonesia that usually have difficult terrain and access. To answer this, we need a technology that can reduce noise from magnetotelluric data and improve the data quality while keeping the cost and time of exploration as low as possible. By using continuous wavelet transform method, the noise from magnetotelluric data can be reduced without the need to use a remote station which makes exploration becomes more efficient. The continuous wavelet transform method processes magnetotelluric data from unfiltered time series domain and changes the domains time series data into a time-frequency domain. Changing processes to a time-frequency uses the continuous wavelet transform method to analyze the existence of the frequency and time of occurrence of noise which is then removed. Data that has been removed will be processed into apparent resistivity and phase vs frequency. The filter results have been done compared to commercial software processing. Where the filter successfully eliminates the presence of transient noise that appears with a frequency range of 30-400 Hz and emergence for 0.2-0.4 seconds. So this filter can be another alternative in noise removal in magnetotelluric data."

"ABSTRAKDaerah Istimewa Yogyakarta merupakan wilayah yang beresiko tinggi terhadap bencana gempabumi mengingat secara tektonik merupakan daerah aktif dengan kegempaan yang tinggi serta tingkat kepadatan penduduk yang relatif tinggi. Data BMKG selama 2008- awal 2015 menunjukkan banyak kejadian gempabumi yang terjadi di Daerah Istimewa Yogyakarta dan sekitarnya, namun banyak gempabumi dangkal memiliki kedalaman yang kurang akurat. Analisis kegempaan membutuhkan data lokasi hiposenter yang akurat. Oleh karena itu relokasi gempabumi diperlukan untuk menunjang analisis kegempaan. Metode Double Difference diterapkan untuk merelokasi data gempabumi. Metode tersebut meminimalkan residual waktu tempuh kalkulasi dan observasi dari sepasang gempabumi berdekatan yang terekam pada stasiun yang sama dengan asumsi raypath kedua gempabumi sama, sehingga kesalahan waktu tempuh akibat model kecepatan yang tidak termodelkan dapat diminimalkan tanpa koreksi stasiun. Hasil dari penelitian untuk zona subduksi menunjukkan pola stress tektonik zona subduksi pada gempabumi dangkal terelokasi dan adanya zona seismik ganda yang menguatkan penelitian terdahulu. Hasil relokasi gempabumi di zona patahan menunjukkan kedalaman Patahan Opak terdangkal mulai dari 3 km hingga terdalam mencapai 17 km. Berdasarkan analisis kegempaan, zona subduksi mengalami aktivitas gempa bumi yang tinggi pada tahun 2014 sampai 2015 dan zona patahan mengalami aktivitas gempabumi yang lebih tinggi di awal periode penelitian dibanding diakhir periode penelitian.

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ABSTRACT

Special Region Yogyakarta has potential seismic hazard for the location is tectonically active with high seismicity and dense population. BMKG data for period 2008 until pre-2015 shows many events occurring in Yogyakarta and surrounding areas, but many shallow earthquakes have depth which is less accurate. Seismic analysis requires accurate hypocenter location data. Therefore relocation is needed to provide seismic analysis. Double Difference method is applied. The method minimizes residuals between calculated and observed travel time of pairs of nearby earthquakes which is recorded on the same station with the assumptions that the raypath is similar, so the travel time errors due to unmodeled velocity structure can be minimized without station correction. The results shows relocated shallow earthquakes followed the tectonic stress trend in subduction zone and double seismic zone which confirmed previous research has appeared. Relocation results in the earthquake fault zone shows the depth of the shallowest Opak Fault ranging from 3 km to the deepest reaches 17 km. Based on the analysis of seismicity, subduction zones experienced high seismic activity in 2014 to 2015 and the fault zone experienced a higher activity at the beginning of the study period compared to the end of the study period."

"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.

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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."