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"Penelitian ini menginvestigasi struktur kecepatan S di Lautan Hindia melalui fitting seismogram, akibat gempa C081499A, Sumatra Selatan dan direkam di stasiun RER, Pulau Reunion, Perancis. seismogram observasi dibandingkan dengan seismogram sintetik dalam domain waktu dan ketiga komponen kartesian secara simultan. Seismogram sintetik dihitung dengan program GEMINI, dimana input awalnya adalah model bumi global Ocean dan PREMAN. Selain itu pada kedua seismogram dikenakan low-pass filter dengan frekuensi corner pada 20 mHz. Analisis seismogram menunjukkan penyimpangan yang sangat kuat pada pengamatan atas waktu tiba, jumlah osilasi dan tinggi amplitudo, pada gelombang permukaan Love dan Rayleigh dan gelombang ruang S. Untuk menyelesaikan simpangan yang dijumpai diperlukan koreksi atas struktur bumi meliputi ketebalan kulit bumi, gradien kecepatan βh dan besar koefisien-koefisien untuk βh dan βv di upper mantle, dan sedikit perubahan pada kecepatan S di lapisan-lapisan bumi hingga kedalaman 400 km. Fitting seismogram diperoleh dengan baik pada waveform fase gelombang, baik waktu tempuh osilasi utama dan jumlah osilasi. Hasil riset ini menunjukkan, bahwa daerah Lautan Hindia mempunyai koreksi atas struktur kecepatan S dengan nilai positif terhadap model lautan. Hasil ini berbeda dengan hasil riset seismologi lainnya.

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The research investigated the S speed of earth structure under Indian Ocean using seismogram fitting, due to the C081499A earthquake, South Sumatra and recorded in the observation station RER at Reunion Island, France. The observed seismogram is compared to its synthetic in time domain and three cartension components simultaneously. Synthetic seismogram is calculated with the GEMINI program, the initial inputs are the global earth models of Ocean and PREMAN. Prior to seismogram comparison, a low-pass filter with corner frequency of 20 mHz is imposed. The result of analysis shows a very strong deviation at the arrival time, oscillation amount and amplitude height of Love and Rayleigh surface waves and S body wave. To overcome the found discrepancies a correction to the earth structure is needed covering the earth crust thickness, speed gradient of βh and zero-order coefficient for the βh and βv in upper mantle, and a little change in S speed in earth layers down to a depth of 400 km. Seismogram fitting is better obtained at waveform of the wave phase, either the travel time or oscillation number of S wave and Love surface wave. The results shows that the Indian Ocean has correction to the S speed structure, which is positive to standard earth model. This result differs from other seismology research."

"In this research the model of earth layers between earthquake's epicenter in Hokkaido Japan and observation station in Black Forest of Observatory (BFO), Germany is investigated. The earth model is 1-D that represents the average speed model. The earth model is obtained by seismogram comparison between data and synthetic seismogram in time domain and three components simultaneously. Synthetic Seismogram is calculated with the Green's function of the Earth by MINor Integration (GEMINI) program, where program's input is initially the earth model IASPEI91, PREMAN and also the Centroid Moment Tensor (CMT) solution of the earthquake. A Butterworth low-pass filter with corner frequency of 20 mHz is imposed to measured and synthetic seismogram. On seismogram comparison we can find unsystematic discrepancies, covering the travel time and waveform of all wave phases, namely on P, S, SS wave and surface wave of Rayleigh and Love. Solution to the above mentioned discrepancies needs correction to the earth structure, that covering the change of earth crust thickness, the gradient of �?�h and value of zero order coefficient in �?�h and �?�v in upper mantle, to get the fitting on the surface wave of Love and Rayleigh. Further correction to accomplish the discrepancies on body waves is conducted on layers beneath upper mantle down to depth of 630 km, where a little change at speed model of P and S wave is carried out. The number of oscillation amount especially on Love wave is influenced by earth crust depth earth. Good fitting is obtained at phase and amplitude of Love wave, but also at amplitude of some body wave too. This effect is not yet been exploited for the determination of moment tensor."

"Kondisi geologi setempat sangat mempengaruhi tingkat risiko bencana di suatu daerah. Jawa timur merupakan wilayah dengan tingkat kerentanan gempabumi cukup tinggi. Oleh karena itu Perlu ada kajian struktur bawah permukaan secara regional sebagai upaya mitigasi bencana gempabumi. Tujuan dari penelitian ini adalah untuk mengetahui model kecepatan gelombang geser, kedalaman bedrock dan mengetahui distribusi kecepatan gelombang geser, frekuensi natural, faktor amplifikasi, dan indeks kerentanan seismik. Sinyal seismik diperoleh dari rekaman seimograf portable dan stasioner yang terpasang di wilayah Jawa Timur dan Madura. Penelitian ini menggunakan metode inversi ambient noise rasio spektrum horizontal dan vertikal (HVSR). Model kecepatan satu dimensi didapatkan dari simulasi pencarian Monte Carlo berdasarkan nilai misfit terbaik. Hasil Penelitian menunjukkan nilai Vs30 Jawa Timur berkisar 168 – 788 m/s dengan ketebalan sedimen berkisar 10 meter sampai lebih dari 200 meter. Klasifikasi jenis tanah berdasarkan SNI 1726:2012 bervariasi yaitu dari jenis tanah lunak (SE) hingga batuan keras (SA). Indeks Kerentanan seismik bervariasi dengan kisaran 0,23 sampai 64,43. Bagian Utara Jawa Timur terutama di zona kendeng memiliki tingkat risiko bencana gempabumi lebih tinggi. Daerahnya meliputi Lumajang, Malang, Pasuruan, Mojokerto, Sidoarjo, Surabaya, Gresik, Jombang, Ponorogo, Bangkalan, dan Sampangan.

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The geological conditions greatly affect the level of disaster risk in an area. East Java is region with a high level of earthquake vulnerability. Therefore, there is need for regional subsurface structure studies as an earthquake disaster mitigation effort. The purpose of this study is to determine the shear wave velocity model, bedrock depth and the shear wave velocity distribution, natural frequency, amplification factor, and seismic vulnerability index. Seismic signals are obtained from portable and stationary seimograph installed in East Java and Madura. This study uses the horizontal and vertical spectrum ambient noise inversion method (HVSR). One-dimensional share wave velocity  models are obtained from Monte Carlo search simulations based on the best misfit values. The results showed that Vs30 East Java values ranged from 168-788 m/s with sediment thickness ranging from 10 meters to more than 200 meters. Classification of soil types based on SNI 1726: 012 varies from the type of soft soil (SE) to hard rock (SA). Index Seismic vulnerability varies from 0,23 to 64,44. The northern part of East Java, especially in the Kendeng zone, has a higher risk of earthquake disaster. The area includes Lumajang, Malang, Pasuruan, Mojokerto, Madiun, Sidoarjo, Surabaya, Gresik, Jombang, Ponorogo, Bangkalan, and Sampang."