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Karakterisasi sumber gempa Yogyakarta 2006 berdasarkan data GPS Sulaeman, Cecep; Dewi, Lestari Cendekia; Triyoso, Wahyu
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no1.20085The southern part of Central Jawa is one of earthquake hazard prone areas in Indonesia an earthquake occurred on May 27, 2006 and had the moment magnitude 6.3. Base on the GPS observation, the characterization of the epicenter and source of this Yogyakarta earthquake can be estimated using the displacement estimation and strain at the measurement point by using a simple kriging and sequential gaussian simulation method. The direction of the displacement and maximum shear strain anomaly in this research was shown by the fault of SW â€“ NE direction and the displacement pattern shows that this fault is left lateral strike slip movement. The positive anomaly of the maximum shear strainis located about 10 km east of Bantul, which suggests as the position of Yogyakarta 2006 earthquake source, with the moment seismic and moment magnitude values are 8.1385 x 1025 dyne cm, and 6.5 respectively. Â Â

Karakterisasi sumber gempa Yogyakarta 2006 berdasarkan data GPS Sulaeman, Cecep; Dewi, Lestari Cendekia; Triyoso, Wahyu
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.3.1.49-56

http://dx.doi.org/10.17014/ijog.vol3no1.20085The southern part of Central Jawa is one of earthquake hazard prone areas in Indonesia an earthquake occurred on May 27, 2006 and had the moment magnitude 6.3. Base on the GPS observation, the characterization of the epicenter and source of this Yogyakarta earthquake can be estimated using the displacement estimation and strain at the measurement point by using a simple kriging and sequential gaussian simulation method. The direction of the displacement and maximum shear strain anomaly in this research was shown by the fault of SW â€“ NE direction and the displacement pattern shows that this fault is left lateral strike slip movement. The positive anomaly of the maximum shear strainis located about 10 km east of Bantul, which suggests as the position of Yogyakarta 2006 earthquake source, with the moment seismic and moment magnitude values are 8.1385 x 1025 dyne cm, and 6.5 respectively. Â Â

Velocity versus Offset (VVO) Estimation Using Local Event Correlation and Its Application in Seismic Processing & Analysis S. Supriyono; Awali Priyono; Wahyu Triyoso; Hilman Mardiyan
Journal of Engineering and Technological Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2013.45.2.2

Conventional velocity analysis is usually done in a relatively spare grid, for instance every half kilometers, during the processing of seismic data. It is very laborious work and very subjective. To deliver an accurate velocity picking, processing geophysicists must have a good understanding of geological background of area being analyzed and experiences. Velocity errors often occur during picking. Proper quality control and checking are a must. A good and reliable velocity field is very important in seismic processing for achieving high-quality seismic images as well as for delivering an accurate depth conversion. The new method presented here, was developed to correct velocity errors automatically by means of residual velocity correction, and to produce an offset-dependent RMS velocity field at the same time. The method is data driven, based on the normal move out equation (NMO) and measuring the local even correlation between adjacent traces. The stacking velocity is derived simply by averaging the velocity field. The proposed method was tested on synthetic and real data examples with good result. The velocity field has certain characteristics related to hydrocarbon presence. Supriyono (2011 and 2012) developed a new DHI method using velocity gradient attributes by cross-plotting the velocity versus offset (VVO). The velocity gradient exhibits high anomalous values in the presence of gas.

Karakterisasi sumber gempa Yogyakarta 2006 berdasarkan data GPS Cecep Sulaeman; Lestari Cendekia Dewi; Wahyu Triyoso
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no1.20085The southern part of Central Jawa is one of earthquake hazard prone areas in Indonesia an earthquake occurred on May 27, 2006 and had the moment magnitude 6.3. Base on the GPS observation, the characterization of the epicenter and source of this Yogyakarta earthquake can be estimated using the displacement estimation and strain at the measurement point by using a simple kriging and sequential gaussian simulation method. The direction of the displacement and maximum shear strain anomaly in this research was shown by the fault of SW – NE direction and the displacement pattern shows that this fault is left lateral strike slip movement. The positive anomaly of the maximum shear strainis located about 10 km east of Bantul, which suggests as the position of Yogyakarta 2006 earthquake source, with the moment seismic and moment magnitude values are 8.1385 x 1025 dyne cm, and 6.5 respectively.

Earthquake Potential Hazard Analysis of Palembang City, Sumatra Island Wahyu Triyoso; Aris Suwondo; Zael Yahd Xanggam Naibaho
Indonesian Journal on Geoscience Vol 8, No 1 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.1.1-9

DOI: 10.17014/ijog.8.1.1-9Most of the destructive earthquakes in Sumatra are dominated by thrust mechanisms that occur due to the process of subduction and some earthquakes with strike-slip fault sources such as the Sumatra fault and northwestern Sumatra. The subduction zones along western Sumatra and Sumatran fault zones are active seismic sources of earthquake events. The seismotectonics of South Sumatra can be affected by earthquakes triggered by these seismic sources. In this study, an estimation and analysis of the potential for earthquake hazard curves were carried out in Palembang City due to the influence of subduction zone sources, strike-slip faults, and intermediate to deep earthquake sources. The algorithm of the seismicity smoothing was applied to estimate the seismicity rate for megathrust sources, active faults, and intermediate to deep earthquake sources. The results of the earthquake hazard potential curve showed that the estimated Peak Ground Acceleration (PGA) in the bedrock of the subduction earthquake sources was greater than the estimated ground shaking due to strike-slip fault sources as well as intermediate to deep earthquake sources. To understand better the potential ground shaking, the evaluation of PGA at the surface was then estimated by including the amplification factor. The amplification factor was calculated using the Horizontal-Vertical Spectral Ratio (HVSR) method. Based on the PGA estimated at the surface of 10% probability exceedance level during 50 years, the Palembang City has a potential shaking of around 35 gal, which is likely to be caused by a megathrust earthquake source.

Estimasi Parameter Koreksi Anisotropi Seismik Melalui Pendekatan Nonhyperbolic Moveout Pada Gather Konvensional, DMO, dan CRS Julius Febriardi; Wahyu Triyoso
Jurnal Geofisika Vol 15 No 1 (2017): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v15i1.404

Sifat anisotropi pada suatu medium menyebabkan adanya perbedaan kecepatan rambat gelombang berdasarkan arah rambatnya. Medium bersifat transvere isotropy memiliki nilai kecepatan yang berbeda ke arah lateral dan vertikal. Medium bersifat vertical transverse isotropy (VTI) memiliki kecepatan lateral yang lebih besar daripada kecepatan vertikal. Perbedaan ini menyebabkan timbulnya efek hockey stick, terutama pada offset jauh. Karena informasi pada offset jauh amat penting, maka efek ini perlu dikoreksi terlebih dahulu sebelum melanjutkan ke tahapan pemrosesan data selanjutnya. Untuk mendapat pemahaman yang lebih baik, maka dibuat model sintetik VTI yang diproses menggunakan normal moveout (NMO), dip moveout (DMO) dan common reflection surface (CRS). Untuk menghilangkan efek dipping dan agar didapatkan hasil velocity analysis yang baik, DMO dan CRS dilakukan. Pilihan ini atas pertimbangan bahwa metode DMO dapat menghilangkan sifat dip- dependent pada gather seismik, dan analisis kecepatan paling mudah dilakukan pada metode CRS. Hasil perbandingan metode DMO dan CRS menunjukkan bahwa CRS menunjukkan S/N ratio yang lebih baik dan memiliki ketidakpastian yang lebih kecil dalam analisis kecepatan yang berpengaruh langsung dalam estimasi parameter koreksi anisotropi. Nilai parameter koreksi anisotropi diestimasi pada CDP yang ditentukan menggunakan pendekatan nonhyperbolic moveout. Nilai rata-rata yang diperoleh pada masing-masing metode menunjukkan hasil yang berbeda. Nilai ηeff yang paling mendekati nilai η model adalah pada metode DMO dan CRS.

Analisis Eliminasi Multiple Menggunakan Metode F-K Filter dan Transformasi Radon Parabola Khayrunnisa Agustina; Wahyu Triyoso
Jurnal Geofisika Vol 15 No 1 (2017): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v15i1.399

Penjalaran gelombang seismik di dalam bumi terpengaruh oleh banyak faktor atau noise yang menyebabkan distorsi, salah satunya adalah gelombang multiple. Gelombang multiple pada beberapa kasus mengganggu citra dari penampang seismik sehingga dapat menyebabkan kesalahan pada saat interpretasi data. F-K Filter dan Transformasi Radon Parabola merupakan metode yang dapat digunakan untuk mengeliminasi multiple yang memanfaatkan perbedaan moveout antara event primer dan multiple dengan mengubah data dari domain t-x ke domain lain setelah sebelumnya dilakukan koreksi NMO. Metode F-K Filter dan Transformasi Radon Parabola diaplikasikan pada data sintetik seismik 2D untuk melihat kelebihan dan kekurangan kedua metode tersebut dalam mengeliminasi multiple dan melihat efek padatrendnilai amplitudo sebelum dan sesudah dilakukan proses eliminasi. Hasil menunjukkan bahwa Transformasi Radon Parabola lebih baik daripada F-K Filter dalam mengeliminasi multiple karena F-K Filter masih menyisakan multiple yang cukup kuat terutama pada near oﬀset.

Study of Converted-Wave Modeling: AVO Application for Shallow Gas Models Natashia Christy Viony; Wahyu Triyoso
Jurnal Geofisika Vol 16 No 2 (2018): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

The application of converted-wave seismic method in hydrocarbon exploration has increased significantly. Since the conventional seismic ceases to provide an adequate result in complex geology area and it provides an ambiguous brightspot response. The main principle is that an incident P-wave produces reflected and converted P and SV wave when the downgoing P-wave impinges on an interface. Converted-wave seismic uses the multicomponent receiver that records both of vertical component and horizontal component. The vertical component is assumed to correspond to the compressional PP wave and the horizontal correspond to the PS converted-wave. In this research, a synthetic model with the shallow gas and the salt dome below are constructed. The purpose of this study is to analyze the brightspot due to the presence of shallow gas and its effect to the quality of PP and PS wave reflection below the gas zone. To achieve the goal, both vertical and horizontal seismic data processing are performed. In horizontal data processing, the best gamma function (Vp/Vs) value is estimated to produce the better and reliable image. The result shows that the brightspot response in conventional data doesn’t exist in converted-wave data and the imaging below the gas zone in converted-wave data is better than the conventional due to the attenuation and diffraction effect that caused by gas column. Processing is followed by AVO analysis to compare the AVO response of PP and PS data in characterizing gas reservoir. Both PP and PS AVO curve shows the consistency with synthetic AVO from well data. Gas reservoir is a class 1 AVO anomaly with positive intercept and negative gradient on PP data. However, PS AVO curve does not refer any anomaly. It is because S-wave is not sensitive to the existence of rock saturant.

Identifikasi Hidrokarbon Gas Dengan Menggunakan Atribut Energy-weighted AVO pada Lapangan Penobscot, Kanada Ashari Aries; Wahyu Triyoso
Jurnal Geofisika Vol 15 No 2 (2017): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v15i2.407

Amplitude Variation with Offset (AVO) adalah teknik yang sering digunakan sebagai indikator keberadaan hidrokarbon pada data seismik. Teknik ini secara matematis menggunakan pendekatan terhadap persamaan Zoeppritz untuk mengidentifikasi perubahan amplitudo sebagai fungsi dari sudut datang dan menghubungkannya dengan sifat batuan dan kandungan fluida yang ada di dalamnya. Pada penelitian ini, atribut baru, Energy-weighted AVO, digunakan untuk mengidentifikasi keberadaan hidrokarbon pada lapangan Penobscot, Kanada. Prinsip utama atribut ini adalah meningkatkan respon anomali yang berkaitan dengan hidrokarbon sekaligus mengatenuasi seismik background di sekitar anomali. Keunggulan atribut ini adalah mampu membedakan respon anomali hidrokarbon terhadap anomali lain yang disebabkan oleh litologi seperti batubara. Selain itu, atribut ini aplikatif terhadap data seismik pre-stack maupun post-stack.

Earthquake Potential Hazard Analysis of Palembang City, Sumatra Island Wahyu Triyoso; Aris Suwondo; Zael Yahd Xanggam Naibaho
Indonesian Journal on Geoscience Vol. 8 No. 1 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.1.1-9

DOI: 10.17014/ijog.8.1.1-9Most of the destructive earthquakes in Sumatra are dominated by thrust mechanisms that occur due to the process of subduction and some earthquakes with strike-slip fault sources such as the Sumatra fault and northwestern Sumatra. The subduction zones along western Sumatra and Sumatran fault zones are active seismic sources of earthquake events. The seismotectonics of South Sumatra can be affected by earthquakes triggered by these seismic sources. In this study, an estimation and analysis of the potential for earthquake hazard curves were carried out in Palembang City due to the influence of subduction zone sources, strike-slip faults, and intermediate to deep earthquake sources. The algorithm of the seismicity smoothing was applied to estimate the seismicity rate for megathrust sources, active faults, and intermediate to deep earthquake sources. The results of the earthquake hazard potential curve showed that the estimated Peak Ground Acceleration (PGA) in the bedrock of the subduction earthquake sources was greater than the estimated ground shaking due to strike-slip fault sources as well as intermediate to deep earthquake sources. To understand better the potential ground shaking, the evaluation of PGA at the surface was then estimated by including the amplification factor. The amplification factor was calculated using the Horizontal-Vertical Spectral Ratio (HVSR) method. Based on the PGA estimated at the surface of 10% probability exceedance level during 50 years, the Palembang City has a potential shaking of around 35 gal, which is likely to be caused by a megathrust earthquake source.

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