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-A shear-wave splitting analysis was determined to observe anisotropic structures of an upper mantle layer beneath Sumatra. The data were collected from 35 BMKG stations with the magnitude of more than 6.25 Mw and the epicentre of 85 o -140 o . A shear-wave splitting measurement was calculated by using Splitlab based on three methods simultaneously. The result of the shear-wave splitting measurement in the Sumatra Forearc and Fault Zone shows that there are two anisotropic layers. The first layer has a dominant-fast-polarization direction that is parallel with a trench, and has the delay time duration of 0.5 -0.9 s-. It is presumed that it is caused by a shear-strain as a result of the existences of Mentawai and Sumatra Fault Zones. The second layer has a dominant-fast-polarization direction that is perpendicular to the trench with the delay time duration of about 1.1 -1.9 s-. It is presumed that it is caused by a movement of a subduction plate on a mantle wedge. The measurement in the backarc shows that there is only one anisotropic layer that is a subduction plate. It is also found that there is a transition of an orientation change on the subduction plate between Sumatra and Java. The change of the polarization direction is probably related to the age difference and the direction velocity of the absolute plate movement (APM) from Sumatra to Java.

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Pencuplikan atau picking gelombang P merupakan kegiatan dasar yang harus dilakukan oleh para peneliti/seismologist untuk menganalisis sinyal gempa bumi. Picking gelombang P apabila tidak dilakukan dengan teliti, akan mengakibatkan proses analisis sinyal gempa menjadi tidak akurat. Sinyal gempa yang baik adalah sinyal yang bebas dari noise, baik noise instrument maupun noise lapangan. Gelombang gempa bumi merupakan sinyal gelombang tiga komponen yang sangat kompleks, sehingga diperlukan metode filtering yang dapat memfilter tiga komponen secara simultan. Metode Ensemble Empirical Mode Decomposition (EEMD) adalah suatu metode dekomposisi sinyal yang dapat diterapkan untuk mereduksi noise. Kelebihan EEMD adalah mampu mereduksi noise pada frekuensi tinggi dan rendah tanpa mengubah dari karakter sinyal, sehingga karakteristik sinyal tidak hilang.Kata kunci: EMD, EEMD, Noise, Sinyal gempa.

Sumur yang sudah tidak bisa berproduksi secara natural, menggunakan metode yang disebut Artificial Lift atau pengangkatan buatan dalam proses produksi minyak dan gas nya. Ada berbagai jenis metode pengangkatan buatan, namun salah satu metode pengangkatan buatan yang digunakan di setiap lapangan sumur PT.Citic Seram Energy Limited Oseil adalah electric submersible pump. Hal ini dikarenakan rata-rata kedalaman bor di lapangan Oseil merupakan sumur yang cukup dalam dengan tipe sumur terarah. Oleh karena itu, penulis harus menganalisis kinerja pompa electric submersible pump dengan melihat kurva Inflow Performance Relationship (IPR) untuk menentukan laju optimal sumur Oseil-X. Kurva hubungan kinerja inflow dapat dilihat dari hubungan antara jalur aliran fluida dengan tekanan aliran bottom hole (Pwf). Untuk sumur Oseil-X sendiri, kurvanya adalah kurva hubungan arus-daya dua fasa. Hal ini terlihat dari nilai tekanan reservoir dan Pwf sumur Oseil-X lebih kecil dari tekanan titik didih . Dari perhitungan inflow performance ratio dapat diketahui bahwa debit maksimum cairan kemudian dibandingkan dengan nilai outflow optimal dan dievaluasi. Nilai flow optimal yang didapat adalah 263,4 BFPD, dengan flow rate yang dihasilkan oleh pompa yang terpasang hanya sebesar 211, sehingga dinilai kurang efisien dan perlu dilakukan penjadwalan ulang oleh perusahaan di masa yang akan datang.

A new approach for quantitative analysis of self-potential (SP) data is introduced. In this paper, anomaly of SP is associated with simple geometric models such as a vertical cylinder, a horizontal cylinder and a sphere object. Then, in order to estimate the depth, the electric dipole moment, the anomaly body’s centre, the geometrical form factor and polarization of the anomaly, the method was developed and implemented. The development and implementation of the method is based on the global optimization concept. This method uses Quantum-behaved Particle Swarm Optimization (QPSO) algorithm to overcome the inversion problem on SP anomaly modelling. The QPSO algorithm was randomly tested on synthetic data which consist of different random noise levels. The result shows a close agreement between the assumed and the measured parameters. At last, the validity of the method was tested on real SP anomaly data and compared to the results given by other advanced inversion approaches.

AbstrakZeolit merupakan material multifungsi yang sering digunakan dalam bidang industri sebagai katalis, ion exchange, adsorber, dll. Dewasa ini telah banyak peneliti yang mempelajari dan mengembangkan teknik sintesis zeolit menggunakan energi baru seperti microwave. Iradiasi microwave terbukti lebih efisien jika diterapkan pada proses kimia maupun fisika. Pada penelitian ini akan dipelajari pengaruh penggunaan microwave terhadap sifat zeolit yang dihasilkan yaitu gugus fungsional pada zeolit. Berdasarkan analisa FTIR pada sampel zeolit sintetis dari abu sekam padi menggunakan modifikasi iradiasi microwave, dapat disimpulkan bahwa kenaikan absorbansi terjadi pada sampel-sampel dengan modifikasi. Hal ini terlihat jelas pada beberapa gugus fungsional seperti Si-OH dan Si-O-Al pada panjang gelombang 3450 cm -1 dan 1000,35 cm -1 . Sehingga dapat disimpulkan bahwa iradiasi microwave dapat meningkatkan proses reaksi pada preparasi zeolit sintetis.

The northern Sumatra consists of several tectonic segments, such as subduction zone, the Sumatra and Mentawai faults. An analysis that can be used to identify the tectonic segments, located beneath the northern Sumatra, is shear wave- splitting. The purpose of the analysis of shear-wave splitting is to monitor the anisotropic characteristics of the structure of the earth layers located beneath the northern Sumatra. The monitoring data were collected from 4 BMKG stations with the magnitude was more than 6.3 Mw and the the range of the epicentral distance was about 85̊-140̊. The data analysis was conducted by using Splitlab program based on rotation-correlation method. The result of the shear-wave splitting analysis shows that there are two anisotropic layers. The delay time found in the first layer is about 0,5-0,9 s, which is assumed that it occurs due to the Sumatran fault. Meanwhile, the delay time found in the second layer is about 1,4-1,8 s, which is assumed that it occurs due to the subduction plate movement on the upper mantle layer. The results of TPTI, TSI and TRSI stations has shown congruence, that is the polarization direction is parallel to the Sumatra fault on the upper layer and the polarization direction is perpendicular to the Sumatra fault on the lower layer. The PSI station shows the polarization direction is different from the other stations, in which they show the polarization direction is perpendicular to the Sumatra fault on the upper layer and the polarization direction is parallel to the Sumatra fault on the lower layer. The difference of the data processing in the PSI station, we assume, is caused by the presence of a complex layer beneath Toba caldera.