APLIKASI DIRECT PRINCIPAL COMPONENT ANALYSIS UNTUK ANALISIS SEBARAN DEPOSIT NIKEL LATERIT PADA DI KABUPATEN SERAM BAGIAN BARAT-PROVINSI MALUKU

Pemetaan mineral alterasi hidrotermal dengan metode penginderaan jauh pada daerah bervegetasi seringkali mendapat gangguan dalam mendeteksi keberadaan endapan mineral, hal ini dikarenakan adanya kemiripan kurva spectral vegetasi dengan kelompok mineral pada citra, yang berakibat kurang akurasi pemetaan. Dari penelitian ini Kerapatan vegetasi yang didapatkan melalui citra satelit pada wilayah penelitian memiliki indeks antara 0,09 – 0,70. Berdasarkan rentan nilai tersebut kondisi kerapatan vegetasi dibagi menjadi tiga kelas yaitu, rendah (< 0,30), sedang (0,30 – 0,60) dan tinggi (> 0,60). menggunakan defoliant technique yaitu metode yang digunakan untuk meningkatkan respon spektral dari mineral permukaan yang didasarkan pada reflektansi (pantulan cahaya) respon spektral mineral dengan vegetasi.  Untuk mineral hematite dan goethite digunakan rasio saluran 1:2 dan 4:3 di mana respon spektral masing-masing mineral pada panjang gelombang 0,4 – 2,5 µm Hasilnya diperoleh bahwa indikasi kehadiran deposit nikel laterit berasosiasi variable fisik sebagai berikut: batuan induk berupa batuan Ultramafik dan Kompleks Taunusa (batuan metamorf), kerapatan vegetasi rendah (NDVI < 0,3), Untuk memperoleh akurasi ekstraksi area sampel (training area) sebagai acuan piksel yang mengandung mineral permukaan. Ketiga, klasifikasi terbimbing (supervised classification) citra hasil olahan, sehingga dapat diperoleh peta zona mineral permukaan

Peningkatan Pengetahuan Tentang Mitigasi Bencana Alam Di SMA Negeri 13 Ambon

Kota Ambon adalah ibuktota provinsi Maluku yang sangat aktif secara tektonik karena terletak pada pertemuan lempeng tektonik. Posisi ini menjadikannya daerah yang sangat rentan terhadap berbagai jenis bencana alam. Untuk menghadapi risiko ini, maka diperlukan Pengetahuan tentang mitigasi dan dampak bencana, terutama bagi pelajar yang merupakan generasi penerus dan bagian penting dalam upaya kesiapsiagaan bencana. Kegiatan ini bertujuan untuk meningkatkan pengetahuan dan kesadaran siswa di SMA Negeri 13 Ambon mengenai mitigasi bencana alam. Tujuan spesifiknya meliputi peningkatan pemahaman siswa tentang jenis-jenis bencana yang mungkin terjadi, teknik mitigasi yang efektif, dan tindakan darurat yang perlu diambil dalam menghadapi bencana. Kegiatan ini dilakukan dengan metode ceramah/penyuluhan oleh tim dosen kepada para siswa di depan kelas. Hasil dari kegiatan ini terlihat dari antusiasme para siswa dalam mengajukan berbagai pertanyaan terkait materi yang disampaikan. Melalui kegiatan ini, diharapkan siswa di Sekolah memperoleh pemahaman yang lebih baik tentang mitigasi bencana. Tidak hanya meningkatkan kesiapsiagaan individu tetapi juga menyebarluaskan informasi ke komunitas. Upaya ini merupakan langkah penting dalam mempersiapkan generasi muda menghadapi tantangan bencana di masa depan

Mineralogy of granites from Hukurila area, Ambon Island, Indonesia: An insight into petrogenesis

The Hukurila area in the Leitimor region of Ambon Island hosts one of the granite bodies. The granite is surrounded by Jurassic-Cretaceous peridotites. Although granites in Ambon Island have been intensively investigated, their origin remains interesting to study. This work offers petrography and X-ray diffraction data of granite from Hukurila area and contributes to understanding petrogenesis in Ambon Island. Granites from Hukurila area are white to light brown and have a medium- to coarse-grained holocrystalline texture, with quartz, potassium feldspars, plagioclase, biotite, and muscovite being the most common minerals. Potassium feldspars are sometimes found in aggregated larger crystals in the outcrops. While cordierite, zircon, apatite, and mullite were also observed as accessory minerals under the microscope. Mullite in granites from Hukurila area indicates that the rocks were subjected to high temperatures. Aluminium-rich minerals (i.e., cordierite and mullite) in granites from Hukurila area suggest S-type granite with significant crustal contamination during their formation

Integrasi SIG (Sistem Informasi Geografis) dan Citra ASTER untuk Analisis Sebaran Deposit Nikel Laterit ( Studi Kasus pada Kabupaten Seram Bagian Barat, Provinsi Maluku)

This research investigates the application of GIS (Geographic Information System) and ASTER image for predicting the occurrences of lateritic nickel depsosits. Research area is located in the Kabupaten Seram Bagian Barat, Maluku Province, which is known to have large amount of lateritic nickel deposits. Research methods consist of interpretation of remote sensing data especially ASTER, field geological works, spatial data management and spatial analysis using GIS. Research is conducted into four stages, starts from data collection and entry which will be used as modeling variables. The next steps consist of processing the ASTER image and digital geology and DEM data, calculation of relationship between physical variables and occurrences of lateritic nickel deposits, data integration, spatial modeling and validation using field data. GIS spatial analysis is applied to quantify spatial relationship between occurrences of nickel deposits (represented by drillhole data) and following geological factors: lithology, structures (lineaments), slope, vegetation cover, and the existence of predictor minerals hematite, goethite, and chlorite. In this case, lithology is derived from geological map, lineaments and slopes from DEM, while vegetation and minerals hematite, goethite and chlorite from ASTER. The result shows that lateritic nickel deposits are associated with seven (7) physical variable as follows: ultramafic rocks and Taunusa Complex (metamorphic rocks), low vegetation density (NDVI < 0,3), low to moderate slope class (< 36%), zone at radii > 300 m from geological lineaments, the presence of indicator minerals hematite and geothite (PCA > 6,09), and the absence of chlorite (PCA < 3,45). Then the seven physical variables are made as seven evidence or predictor maps using binary method (Suitable and Non-suitable class) which are then all combined using spatial operator AND to produce a map of potential lateritic nickel deposits. This modeling produces areas of potential lateritic nickel deposits that covers 14.05 sq. km. that equals approximately with 10% of the total of study area which is 142.01 sq. km. This result has been succesfully verified using field data that shows a good correlation between GIS model and field data. This methoid is expected can be applied to identify the potency of lateritic nickel deposits in other regions of Indonesia

Aftershock study of the 2019 Ambon earthquake using moment tensor inversion: identification of fault reactivation in northern Banda, Indonesia

Abstract On September 26, 2019, an Mw 6.5 earthquake occurred 23 km northeast of Ambon City, Indonesia, followed by numerous aftershock series related to a complex fault network reactivation in the Ambon and Seram region. Using moment tensor inversion, we identify the kinematics of fault reactivation based on the focal mechanism solution of 20 aftershocks with Mw > 3.2 and analyze the earthquake sequence from both focal mechanism solutions and spatiotemporal seismicity. The MTs solution of aftershocks revealed three different characteristics of fault reactivation: (i) a 35 km long N-S oriented main fault characterized by dextral strike-slip (ii) a NE-SW reverse fault segment with a ~ 55° northeastward dip located in southwest Seram, and (iii) two strike-slip segments (NNW-SSE and NNE-SSW trends) and an E-W normal fault in Ambon Island. Analysis of spatiotemporal seismicity with the MTs solution suggests that the Mw 6.5 Ambon aftershock sequences can be described as follows: (i) an Mw 6.5 mainshock rupture that was primarily made up of a major strike-slip component and an insignificant minor normal fault; (ii) first aftershock cluster propagate along the main N-S ruptures, followed by the strike-slip and normal cluster in Ambon Island (iii) The reverse fault events cluster appeared next in Southwest Seram. The presence of complex strike-slip segments in Ambon agrees with the regional structure trends in Halmahera, located in the north of the study area, while the E-W oriented normal fault might be related to the eastward velocity increase in Banda Arc, which causes extensional deformation. Given that the fault reactivation identified in Ambon and Seram is located close to the densely populated urban regions of Ambon City and Kairatu, the analysis of future seismic hazards related to this fault reactivation should consider the risks in a region with complex fault settings. Graphical Abstrac

Ambient Seismic Noise Cross - correlation of Ambon Island and Surrounding Area, Eastern Indonesia: Preliminary Result

Abstract The island of Ambon lies on complex tectonics, part of Banda Arc which is driven by the Australia – Eurasia collision. Historical earthquake data show that an earthquake resulting the greatest tsunami in Indonesia had occurred at Ambon Island. On 26 September 2019, Ambon was shaken by an M 6.5 earthquake at a depth of 10 km (BMKG). In this study, we use ambient noise data from 11 temporary stations deployed by ITB and 4 permanent stations owned BMKG which are recorded from October until December 2019. Here, we purely use the vertical component of seismogram to retrieve the Empirical Green’s Function of Rayleigh waves. Cross-correlations were obtained from the daily data series and stacked the day-by-day cross-correlation data into one inter-station cross-correlation. The Empirical Green’s Function is seen at the band period 1-15 s. As a part of our study, we analyze the Green’s Function with frequency-time analysis (FTAN) to get Rayleigh wave group velocity. The group velocity of Rayleigh waves varies from 1.04 km/s – 3.75 km/s. Low group velocity might be indicated the presence of sediment or volcanic deposits and high group velocity might be indicated metamorphic rocks. The result of this study might give a finer velocity model of the shallow crustal beneath Ambon Island and the surrounding area.</jats:p