Pendugaan Posisi Dapur Magma Gunungapi Inelika, Flores, Nusa Tenggara Timur Berdasarkan Survei Magnetik

Gunungapi Inelika, Flores, Nusa Tenggara Timur merupakan salah satu gunungapi muda berumur kuarter yang digolongkan aktif dan merupakan gunungapi tipe A. Gunungapi Inelika menampakkan kerucut gunungapi strato. Pada bagian selatan gunungapi ini, terdapat sumber air panas yang merupakan indikasi adanya potensi sumber panas bumi dimana kemungkinan dapat diindikasi kondisi dapur magma di bawah permukaan. Metode magnetik merupakan salah satu metode yang memberikan gambaran tentang sebaran kemagnetan di permukaan bumi. Data yang digunakan merupakan data magnetik sekunder tahun 2010 dimana setelah dilakukan berbagai koreksi antara lain koreksi diurnal dan koreksi IGRF, diketahui nilai anomali magnetik total gunungapi Inelika adalah -537,9 hingga 189,9 nT. Interpretasi secara kualitatif dilakukan untuk mengetahui pola kontur anomali magnetik pada daerah pengukuran. Untuk mempermudah dalam penginterpretasiannya dilakukan pengolahan data yang dikenal dengan pengangkatan (Upward Continuation) dan pengkutuban (Reduce to pole). Interpretasi kuantitatif dilakukan dengan membuat model hasil slicing (sayatan) pada kontur anomali magnetik untuk mengetahui kondisi bawah permukaan. Dengan model bawah permukaan ini dapat diindetifikasi bahwa terdapat dapur magma di daerah barat daya

Mechanism of High Frequency Shallow Earthquake Source in Mount Soputan, North Sulawesi

DOI: 10.17014/ijog.v6i3.122Moment tensor analysis had been conducted to understand the source mechanism of earthquakes in Soputan Volcano during October - November 2010 period. The record shows shallow earthquakes with frequency about 5 - 9 Hz. Polarity distribution of P-wave first onset indicates that the recorded earthquakes are predominated by earthquakes where almost at all stations have the same direction of P-wave first motions, and earthquakes with upward first motions.In this article, the source mechanism is described as the second derivative of moment tensor, approached with first motion amplitude inversion of P-wave at some seismic stations. The result of moment tensor decomposition are predominated by earthquakes with big percentage in ISO and CLVD component. Focal mechanism shows that the recorded earthquakes have the same strike in northeast-southwest direction with dip about 400 - 600. The sources of the high frequency shallow earthquakes are in the form of tensile-shear cracks or a combination between crack and tensile faulting

Hypocenter Relocation of Volcanic Earthquake at Agung Vulcano

Agung Volcano is a stratovolcano located in the area of Karangasem regency of Bali and is in the northwest-southeast fault alignment with Batur, Abang and Seroja Volcano. The existence of this alignment allegedly related to the fracture in the northwest of the island of Bali. The eruption of Agung Volcano recorded on November 25th, 2017 was a significant danger for people living around it. Therefore, it is necessary to monitor the activity of Agung Volcano. The method used in this study is the relocation of volcanic earthquake sources to determine the location of the source of the earthquake which caused an increase in Mount activity. Hypocenter relocation was carried out on 138 earthquake events during October 2017-January 2018 using the Coupled Velocity-Hypocenter method. Hypocenter was obtained at a depth of less than 10 km under sea level with an RMS value <0.3 seconds, and this is thought to have a flow of magma fluid through the conduit which moves towards the earth's surface and triggers an eruptio

Identifikasi Zona Reservoir Panas Bumi Gunung Ijen Jawa Timur Berdasarkan Pemodelan 2 Dimensi Anomali Geomagnetik

Komplek Gunung api Ijen merupakan prospek panas bumi yang terletak di Kabupaten Bondowoso, Jawa Timur. Sistem panas bumi Gunung api Ijen ditandai oleh kawah danau berfluida asam dan solfatara bertemperatur tinggi. Beberapa batuan teralterasi di dekat Gunung Kukusan dan sekelompok mata air panas Blawan di bagian utara kaldera. Pengukuran magnetik dilakukan pada 175 titik tersebar di dalam kaldera melingkupi kawah Gunung Ijen hingga Gunung Merapi. Anomali intensitas magnetik total diperoleh melalui koreksi standard IGRF dan variasi diurnal. Metode reduksi ke kutub (RTP) diterapkan dengan inklinasi geomagnet sekitar -32°. Secara umum, hasil penelitian menunjukkan bahwa anomali magnetik tinggi berasosiasi dengan jalur patahan yang menghasilkan pembentukan gunung api baru di bagian selatan, Sedangkan anomali magnetik rendah berada berdekatan dengan kawah Ijen dan Gunung Merapi di bagian timur. Anomali yang rendah ditafsirkan oleh dua kemungkinan pengaruh demagnetisasi batuan akibat kontak termal atau pengaruh remanen batuan dengan umur geologi tertentu menghasilkan polaritas reversal. Anomali intensitas magnet total tinggi pada komponen regional berada 50 hingga 114 nT dan anomali rendah berada di kisaran -850 hingga –750 nT, hal ini ditafsirkan bahwa potensi batuan panas di Komplek Gunung api Ijen tersebar sesuai keberadaan kaldera dan jalur gunung api muda. Prospek batuan panas berkorelasi dengan Formasi batuan gunung api muda dan intrusi magmatic hasil proses pembentukan gunung api berumur Kuarter

Magnetic Source of Kawah Ijen and Subsurface Delineation from Magnet Data

A ground magnetic survey was conducted at Ijen caldera complex. The Ijen caldera complex hosts a large number of volcanic edifices which consists of twelve cinder cones. The youngest of these cinder cones is Kawah Ijen volcano. Magnetic survey is used to delineate the subsurface structures and to estimate the magnetic sources depth of the selected area. Edge enhancement using total horizontal derivative is mainly used to delineate the subsurface structures while the 3D Euler deconvolution is used not only to delineate major subsurface structures but also to determine the structural indices of them as well as the depth of the magnetic sources. The calculated structural indices show that the area is mainly affected by source which interpreted to be related to fault and contact/ thin sheet. Estimated source location shows that source beneath Kawah Ijen are connected to Jampit, Rantih and Merapi as rim volcanoes. Edge enhancement using total horizontal derivative represent the delineation of subsurface structure trending southwest - northeast, coincide with the fault orientation of survey area based on geological map

インドネシア・グントール火山以南の地震活動

グントールはインドネシア・西ジャワのバンドン市の南東35kmにある火山群である。19世紀まで半ばまで頻繁に山頂のグントール火口において爆発的噴火を繰り返してきたが，1943年の噴火を最後に160年以上噴火が発生していない。一方，火山性地震及び周辺の地震活動は活発であり，今後の火山活動を予測する上で地震活動は重要な指標となる．火山地質災害軽減センターが火山監視用に設置した観測点に加え，グントール火山周辺の8点に地震計を設置した。2009年1～3月まではグントール火山の南にあるチクライ山の東山麓で地震活動が活発であった。5月以降12月まではダラジャット地熱地帯における地震活動が活発となり，地震の震源は北西?南東方向の深さ2-9kmに配列することが分かった。Guntur is a volcano complex located 35 km SE of Bandung, West Java, Indonesia. Explosive eruptions frequently occurred at Guntur crater during the period from 1690 to the middle of 19th century, however, no eruption has occurred for 167 years after the 1843 eruption. In spite of dormancy of eruptivity, seismicity of the Guntur volcano is high and earthquake swam sometimes occurred. In order to locate the earthquakes in wider area around the volcano, we installed 8 temporary stations around the volcano in addition to the permanent seismic stations operated by CVGHM at volcanoes around Guntur. Hypocenters were aligned from north to south at eastern flank of the Cikuray volcano, south of Guntur, at depths around 6 km from January to April, 2009. After May, earthquake origins were distributed around Darajat geothermal area at depths 2-9 km, showing alignment from NW to SE.グントールはインドネシア・西ジャワのバンドン市の南東35kmにある火山群である。19世紀まで半ばまで頻繁に山頂のグントール火口において爆発的噴火を繰り返してきたが，1943年の噴火を最後に160年以上噴火が発生していない。一方，火山性地震及び周辺の地震活動は活発であり，今後の火山活動を予測する上で地震活動は重要な指標となる．火山地質災害軽減センターが火山監視用に設置した観測点に加え，グントール火山周辺の8点に地震計を設置した。2009年1～3月まではグントール火山の南にあるチクライ山の東山麓で地震活動が活発であった。5月以降12月まではダラジャット地熱地帯における地震活動が活発となり，地震の震源は北西?南東方向の深さ2-9kmに配列することが分かった。Guntur is a volcano complex located 35 km SE of Bandung, West Java, Indonesia. Explosive eruptions frequently occurred at Guntur crater during the period from 1690 to the middle of 19th century, however, no eruption has occurred for 167 years after the 1843 eruption. In spite of dormancy of eruptivity, seismicity of the Guntur volcano is high and earthquake swam sometimes occurred. In order to locate the earthquakes in wider area around the volcano, we installed 8 temporary stations around the volcano in addition to the permanent seismic stations operated by CVGHM at volcanoes around Guntur. Hypocenters were aligned from north to south at eastern flank of the Cikuray volcano, south of Guntur, at depths around 6 km from January to April, 2009. After May, earthquake origins were distributed around Darajat geothermal area at depths 2-9 km, showing alignment from NW to SE