STUDI DEFORMASI PERMUKAAN PUNCAK GUNUNG MERAPI PADA TAHUN 1993 – 1995, DI PERBATASAN PROVINSI DAERAH ISTIMEWA YOGYAKARTA DAN JAWA TENGAH

Secara geografis, lokasi penelitian terletak pada koordinat X1: 438120mE; Y1: 9167090mN; X2: 439750mE; Y2: 9167090mN; X3: 439750mE; Y3: 9165680mN; dan X4: 438120mE; Y4: 9165680mN. Penelitian menggunakan data sekunder, data deformasi telah diperoleh melalui pengukuran GPS pada periode 1993-1995(Beauducel, 1998) berupa koordinat dan vektor perpindahan titik GPS puncak pada periode 1993-1995, data tersebut menunjukkan pola deformasi yang tidak simetris. Bersumber pada penelitian oleh Aisyah dan kawankawan (2018),menerangkan deformasi tidak simetris tahun 2006 dan 2010 yakni dengan penggunaan metode kombinasi block movement serta inflasi sumber tekanan, maka pada periode 1994-1995 dapat dijelaskan menggunakan metode yang sama, sementara itu pada periode 1993-1994 hanya diterapkan inflasi sumber tekanan. Geomorfologi yang terdapat di puncak Gunung Merapi adalah bentuk asal vulkanik, dengan bentuk lahan berupa lereng aliran lava (V1), lereng endapan aliran piroklastik (V2), kawah (V3) serta kubah lava (V4). Pola pengaliran yang berkembang yakni radial sentrifugal. Diskontinuitas struktural pada puncak Gunung Merapi berupa rekahan dan batas antara bekas aliran lava. Vulkanostratigrafi (sumber erupsi) pada puncak Gunung Merapi dapat dibagi menjadi Merapi Tua (Satuan Aliran Lava Andesit Piroksen Merapi 2) dan Merapi Muda (Satuan Aliran Lava Andesit Piroksen Merapi 3, Satuan Endapan Aliran Piroklastik Muda dan Guguran Merapi, serta Satuan Aliran Lava Andesit Piroksen Merapi 4). Terdapat dua blok yang bergerak secara signifikan, masing-masing diperkirakan bergerak ke arah barat laut dan selatan-barat daya. Perkiraan lokasi sumber tekanan pada periode 1993-1994 yakni 600 m di bawah puncak Gunung Merapi, sementara itu pada periode 1994-1995 sekitar 740 m dibawah puncak. Pada periode 1993-1994 diestimasikan total nilai perubahan volume injeksi magma yakni sebesar 80.8 x, sedangkan periode 1994-1995 total perubahan volume injeksi magma diperkirakan sebesar 90.8 x. Pergerakan blok ke arah barat laut dan selatan-barat daya disebabkan perubahan volume serta tekanan pada sumber, yang dikontrol oleh diskontinuitas struktural di sekitar puncak berupa rekahan maupun batas antara bekas aliran lava, di bagian barat laut berupa batas antara aliran lava 1957 dan 1888, selanjutnya di bagian selatan yakni batas antara lava 1911-1913 dan lava 1888-1909.Kata kunci: Gunung Merapi, Deformasi, GPS, Block movement, Sumber Tekanan

２００６年及び２０１０年メラピ火山噴火に先行する地盤変動の圧力源・ブロック移動複合モデルによる解析

京都大学0048新制・課程博士博士(理学)甲第21330号理博第4426号新制||理||1636(附属図書館)京都大学大学院理学研究科地球惑星科学専攻(主査)教授 井口 正人, 教授 福田 洋一, 教授 大倉 敬宏学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDGA

KOMBINASI MODEL MOGI DAN YOKOYAMA UNTUK ESTIMASI LOKASI SUMBER TEKANAN DAN VOLUME SUPLAI MAGMA GUNUNG MERAPI PERIODE TAHUN 2011-2013

Merapi volcano is a strato volcano located at the border of central Java Provinces and Yogyakarta Special Region, Indonesia. After a big eruption on 2010, Merapi has erupted with VEI (Volcano Explosion Index) I that are occurred on 15 July 2012, 22 July 2013 and 18 November 2013. The study of these characteristic eruptions is one indicator of volcano hazard mitigation, therefore this research have a purpose to modeling the location of the source of pressure and magma supply volume at Merapi Volcano in period 2011 to 2013. Three GPS (Global Positioning System) stations installed on December 2010 and five additional stations on June 2013. The GPS shown extension of the baselines beyond the summit crater, it means that Merapi has already entered into inflation process. The lengthening of the baselines from the summit to the navigation stations is about 5 mm to 15 mm and the displacement of GPS point varied in 2 mm to 50 mm. Estimation of the location of the pressure source and magma supply volume has been done using Mogi and Yokoyama models. The result shown the depth of pressure source before eruption on 15 July 2012 is 9.8 km and the magma supply volume about 45 million m3. Eruption 22 July 2013 and 18 November 2013 are controlled by the dual mechanism of the pressure source at 10.9 km and 4.5 km. Eruption 18 November 2013 controlled by the pressure source at 8.1 km and 2.9 km. Magma supply volume for these eruptions is about 10 million m3. Based on this study, it is known that eruptions are controlled by the pressure source from the internal activities of Merapi volcano

ANALISA DEFORMASI UNTUK PREDIKSI SUMBER TEKANAN MAGMA MENGGUNAKAN DATA GPS (STUDI KASUS: GUNUNG MERAPI, DAERAH ISTIMEWA YOGYAKARTA)

Gunung Merapi adalah salah satu gunungapi paling aktif di Indonesia yang terletak di Provinsi Daerah Istimewa Yogyakarta dan Jawa Tengah. Gunung Merapi memiliki periode letusan yang relative cepat yaitu sekitar 4 tahun sekali. Dengan aktivitas vulkanik yang tinggi dapat mengakibatkan perubahan deformasi pada tubuh Gunung Merapi pada bulan September 2013-Maret 2014. Metode yang digunakan pada penelitian ini adalah metode deformasi dengan menggunakan alat ukur GPS. Karakteristik deformasi yang dikaji meliputi posisi, arah, dan besar pergeseran. Software yang digunakan adalah scientific software GAMIT. Untuk prediksi sumber tekanan mengggunakan model Mogi. Dari hasil analisa yang dilakukan mulai bulan September 2013 sampai 31 Maret 2014, didapatkan nilai pergeseran horisontal untuk stasiun DELS  sebesar 0.010801005 dan vertikal sebesar -0.02366, pergeseran horisontal untuk stasiun GRWH sebesar 0.046374924 dan vertikal sebesar 0.04096, dan pergesreran horisontal untuk stasiun KLAT sebesar 0.013173629 dan vertikal sebesar -0.01479. Nilai tersebut mengindikasikan bahwa tubuh gunung Merapi sedang mengalami deformasi dengan sifat deformasinya adalah inflasi. Sedangkan posisi pusat tekanan magma adalah 7°32’2.129” LS ;110°26’51.57’ BT dengan kedalaman ± 7140.5084 m relatif dari puncak. Volume magma adalah 41788427.5957 m³dan dapat digunakan untuk prediksi skala erupsi mendatang.<br /

Simulation of block-and-ash flows and ash-cloud surges of the 2010 eruption of Merapi volcano with a two-layer model

International audienceA new depth-averaged model has been developed for the simulation of both concentrated and dilute pyroclastic currents and their interactions. The capability of the model to reproduce a real event is tested for the first time with two well-studied eruptive phases of the 2010 eruption of Merapi volcano (Indonesia). We show that the model is able to reproduce quite accurately the dynamics of the currents and the characteristics of the deposits: thickness, extent, volume, and trajectory. The model needs to be tested on other well-studied eruptions and the equations could be refined, but this new approach is a promising tool for the understanding of pyroclastic currents and for a better prediction of volcanic hazards. Plain language Summary Pyroclastic currents are composed of hot gas and rock fragments. They are very dangerous, and their complex behavior makes the related hazards difficult to predict. They are generally formed of two distinct parts: (1) a basal flow that carries ashes and large blocks (up to cubic meters) that is very destructive but follows existing valleys and (2) a dilute part, called pyroclastic surge, that carries ashes in hot turbulent gases. This part is less destructive for infrastructures, but it is less confined by the topography, escapes easily from the valleys, and is very dangerous for the inhabitants. A new numerical model has been developed to simulate their emplacement. It is tested here with the eruption of Merapi volcano in 2010. We show that the model reproduces the main characteristics of the real phenomenon. This new model gives promising perspectives for the understanding of pyroclastic current emplacements and for future estimation of related hazards and impacts on the population, the infrastructure, and the environment

Simulation of block-and-ash flows and ash-cloud surges of the 2010 eruption of Merapi volcano with a two-layer model

International audienceA new depth-averaged model has been developed for the simulation of both concentrated and dilute pyroclastic currents and their interactions. The capability of the model to reproduce a real event is tested for the first time with two well-studied eruptive phases of the 2010 eruption of Merapi volcano (Indonesia). We show that the model is able to reproduce quite accurately the dynamics of the currents and the characteristics of the deposits: thickness, extent, volume, and trajectory. The model needs to be tested on other well-studied eruptions and the equations could be refined, but this new approach is a promising tool for the understanding of pyroclastic currents and for a better prediction of volcanic hazards. Plain language Summary Pyroclastic currents are composed of hot gas and rock fragments. They are very dangerous, and their complex behavior makes the related hazards difficult to predict. They are generally formed of two distinct parts: (1) a basal flow that carries ashes and large blocks (up to cubic meters) that is very destructive but follows existing valleys and (2) a dilute part, called pyroclastic surge, that carries ashes in hot turbulent gases. This part is less destructive for infrastructures, but it is less confined by the topography, escapes easily from the valleys, and is very dangerous for the inhabitants. A new numerical model has been developed to simulate their emplacement. It is tested here with the eruption of Merapi volcano in 2010. We show that the model reproduces the main characteristics of the real phenomenon. This new model gives promising perspectives for the understanding of pyroclastic current emplacements and for future estimation of related hazards and impacts on the population, the infrastructure, and the environment

Simulation of block-and-ash flows and ash-cloud surges of the 2010 eruption of Merapi volcano with a two-layer model

International audienceA new depth-averaged model has been developed for the simulation of both concentrated and dilute pyroclastic currents and their interactions. The capability of the model to reproduce a real event is tested for the first time with two well-studied eruptive phases of the 2010 eruption of Merapi volcano (Indonesia). We show that the model is able to reproduce quite accurately the dynamics of the currents and the characteristics of the deposits: thickness, extent, volume, and trajectory. The model needs to be tested on other well-studied eruptions and the equations could be refined, but this new approach is a promising tool for the understanding of pyroclastic currents and for a better prediction of volcanic hazards. Plain language Summary Pyroclastic currents are composed of hot gas and rock fragments. They are very dangerous, and their complex behavior makes the related hazards difficult to predict. They are generally formed of two distinct parts: (1) a basal flow that carries ashes and large blocks (up to cubic meters) that is very destructive but follows existing valleys and (2) a dilute part, called pyroclastic surge, that carries ashes in hot turbulent gases. This part is less destructive for infrastructures, but it is less confined by the topography, escapes easily from the valleys, and is very dangerous for the inhabitants. A new numerical model has been developed to simulate their emplacement. It is tested here with the eruption of Merapi volcano in 2010. We show that the model reproduces the main characteristics of the real phenomenon. This new model gives promising perspectives for the understanding of pyroclastic current emplacements and for future estimation of related hazards and impacts on the population, the infrastructure, and the environment

Monitoring the rainfall intensity at two active volcanoes in Indonesia and Japan by small-compact X-band radars

The 3rd International Conference of Water Resources Development and Environmental Protection 12-13 October 2019, MalangSince 2015, collaborative research conducted by Indonesian and Japan scientists has initiated the installation of small X-band Multi-Parameter (X-MP) radars to mitigate the occurrence of rainfall-induced lahar in three active volcanoes in Indonesia and Japan: Merapi, Sinabung, and Sakurajima. This paper discusses the technical aspects of data acquisition, processing, and performance of the X-MP radar at the Merapi and Sakurajima volcanoes by comparing the estimated rainfall intensity acquired by the radar to three empirical radar-rainfall algorithms. The algorithms are based on radar reflectivity factor (ZHH), specific differential phase shift (KDP), and differential reflectivity (ZDR). A new method of Constant Altitude Plan Position Indicator (CAPPI) interpolation by linear regression is also proposed for a more efficient computation. The first algorithm by Marshall-Palmer, which relies on ZHH, gave the lowest average and maximum rainfall values compared with the other algorithms for all rainfall event cases. On the other hand, the other two algorithms, which involve the MP of radar by Bringi and Chandrasekar and Park et al., gave closer rainfall intensity values with the estimated rainfall intensity acquired by the X-MP radar. These three rain rates give a closer temporal fluctuation when they are compared to the rain gauge-based rainfall intensity