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Jurnal Geofisika

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Published by Himpunan Ahli Geofisika Indonesia

ISSN : 0854352 EISSN : 24776084 DOI : https://doi.org/10.36435/jgf

Core Subject : Science,

Earth & Planetary Sciences Energy Physics

Jurnal Geofisika [e-ISSN : 2477-6084] is a scientific journal published by Himpunan Ahli Geofisika Indonesia (HAGI). This journal is referenced, each paper was assessed and evaluated by editors and reviewers who are experts in the relevant fields and come from education institutions and industry, both from within and outside the country. The published article covers all science and technology including Geophysics, Meteorology, Oceanography, Geology and Geodesy.

Arjuna Subject : Ilmu Bumi dan Planet (semua kategori) - Geofisika

Articles 75 Documents

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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.

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.

Interpretation of Dynamic Sediment Characteristic Based on Microtremor Analysis in Prambanan Region, Sleman Yogyakarta and Klaten Central Java, Indonesia Hesti Hesti; Subagyo Pramumijoyo; Djoko Wintolo
Jurnal Geofisika Vol 16 No 1 (2018): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Yogyakarta earthquake on Mei 27, 2006 caused Prambanan area get quite severe damage marked by damageof resident house and Prambanan Temple.This study was conducted using data of microtremorsingle station and Yogyakarta earthquake 27 May 2006. Data were analyzed with microtremor HVSR methods to get the value of the dominant frequency (fo) and amplication (Ao).Furthermore, calculated the value of peak ground acceleration (PGA) in the layers of sedimen bedrock and seismic vulnerability index (Kg) to get ground shear strain value. Prambanan area has a dominant frequency (fo) value ranges from 0.63-6.78 Hz. Ground shear strain valueranges from 3,55.10-5 - 4,04.10-2.Each of these factors is then mapped with a division of 4 zones is very high, high, medium, and low.Based on the analysis of all these factors Prambanan area is an area that is vulnerable to the risk of earthquake events.

Analysis of the Donggala-Palu Tsunami Characteristics based on Rupture Duration (Tdur) and Active Fault Orientation using the HC-plot Method Ramadhan Priadi; Angga Wijaya; Maria Annaluna Pasaribu; Riska Yulinda
Jurnal Geofisika Vol 17 No 1 (2019): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

September 28th, 2018, Donggala-Palu earthquake M 7.5 occurred at depth of 12 km and generated tsunami to be released off the coast in Palu Bay. The tsunami that occurred in Palu was very interesting because the results of the earthquake source mechanism Palu had a type of strike-slip fault that should not have generated a tsunami. This study purpose to estimate the characteristics of the Donggala-Palu tsunami based on rupture duration ( and orientation fault activated using the HC-plot method. The data used in this study are data waveforms from 17 seismic stations and CMT Global catalog data with the area of research 0.87 0 N-1.78 0S dan 118.640E- 120.95 0E. The waveform data used is a phase P-PP vertical component signal with a Bandpass-filter 1-5 Hz for determination . The fastest rupture duration from the earthquake source is obtained from the calculation of each station. Delay time measurement after P wave for 90% (T0.9), 80% (T0.8), 50% (T0.5), dan 20% (T0.2) from its peak value. Then the HC-plot method is used to estimate the orientation of generator fault Palu earthquake and the direction of rupture from the focal mechanism. From the results of processing obtained 2 pairs of seismic stations with almost the same distance but with different azimuths. The fastest rupture duration is at BBSI station with value of 82.014 s and distance from station to epicenter . So that the rupture direction is in the azimuth from the north. The result of fault orientation was obtained hypocenter distance to the centroid for nodal plane 1 is 6.32 km and nodal plane 2 is 30.17 km with distance centroid to hypocenter is 31.22 km. So in Palu earthquake, the tsunami generator fault was in nodal plane 1 with direction north-south. Criteria obtained indicate that the Palu earthquake M 7.5 has potential for a tsunami because of its value has meet ≥ 65 s, but from the result of the focal mechanism direction field not passing through the Palu bay is thought to be another parameter that generates a tsunami and Palu koro fault line uncharted.

Pemodelan Penyebaran Massa CO2 Terinjeksi dalam reservoir untuk Mendapatkan Respon Anomali Time-lapse microgravity di Permukaan Dinda Rahmani; Darharta Dahrin
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.v15i2.408

Dalam proyek CCS, monitoring bawah permukaan perlu dilakukan dengan baik agar CO2 yang diinjeksikan dapat tersimpandengan aman di dalam reservoir. Salah satu metode geofisika yang dapat digunakan untuk monitoring bawah permukaan adalah metode gravity. Dengan membuat model sintetik volume reservoir, tekanan dan temperatur bawah permukaan, serta perhitungan aliran fluida pada rentang waktu tertentu, dapat diprediksi radius penyebaran CO2 dan distribusi densitasnya di dalam reservoir. Radius penyebaran dan kontras densitas yang didapatkan, digunakan untuk pemodelan ke depan time-lapse microgravity dengan menggunakan software MATLAB versi R2012a yang telah divalidasi dengan software yang sudah ada sebelumnya, GRAV3D versi 2.0. Berdasarkan perhitungan dan pemodelan yang telah dilakukan, diketahui peningkatan tekanan bottomhole mengakibatkan perubahan sifat fisis CO2 yang mempengaruhi radius penyebarannya. Kemudian, respon anomali time-lapse microgravity yang dihasilkan menunjukkan kecenderungan nilai anomali yang terus meningkat seiring bertambahnya massa CO2 yang diinjeksikan. Nilai anomali setengah maksimum dan radius yang didapatkan pada hari ke 720, yaitu 1,323 x 10-1µGal dan 631,688 m untuk penyebaran massa CO2 di dalam reservoir sejauh 96,436 m. Dari kurva perbandingan tekanan reservoir terhadap tekanan fracture dan litostatik pada hari ke 720, didapatkan nilai tekanan pada kedalaman reservoir yang diinjeksikan CO2 masih jauh di bawah tekanan fracture dan litostatik, sehingga penambahan massa dari injeksi CO2 yang dimodelkan ini sangat kecil berpotensi untuk menimbulkan rekahan baru pada formasi. Dengan demikian, hasil pemodelan penyebaran CO2 dan distribusi densitasnya dalam reservoir, yang dikaitkan pula dengan perbandingan tekanan reservoir terhadap tekanan fracture dan litostatik, dapat digunakan untuk menentukan aman atau tidaknya injeksi CO2 yang dimodelkan.

Relocation and Focal Mechanism of Aftershocks Pidie Jaya Earthquake (Mw6.5) Dec 7th, 2016 using BMKG Network Pepen Supendi; Andri D. Nugraha; Tony Agus Wijaya
Jurnal Geofisika Vol 15 No 3 (2017): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

We have successfully relocated 74 out of 89 aftershocks until December 19, 2016, by using hypocenter double-difference method. We also have conducted focal mechanism analysis to estimate the type of fault slip. The results indicate improvement in hypocenter location, where the initial earthquakes focus depth at a fixed depth of 10 km have been updated and have described the patterns of active fault in the area trending Northwest-Southeast. The validity through the histogram of travel-time residual shows fairly good data processing where the residual value is close to zero (t.obs - t.cal ~ 0). Based on focal mechanism solutions of mainshock and two selected aftershocks, the type of fault is right lateral strike-slip.

Aquifer Area Investigation Using Resistivity Method in Cikopomayak, West Java, Indonesia Josua Washington Sihotang; Rodrigo Osvaldus; Danny Bona Tua Munte; Nasib Priono; Febriwan Mohamad
Jurnal Geofisika Vol 16 No 3 (2018): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Administratively, the research area is located in around Cikopomayak Village, Jasinga, Bogor, West Java,Indonesia. Based on the Hydrogeological and Groundwater Basin Map, this research area was classied to non-potential groundwater basin. In addition, when the summer comes, the lack of water will be happened around the area. Consequently, the water reserve wasn't enough to fulll the necessity of freshwater. Thus, the research about identifying aquifer location was needed. This research aims to determine the depth and thickness of aquifer for the alternative ways to overcome the problem, particularly, for the Cikopomayak Village. Theresearch used the geophysical method by modeling the several data such as Geoelectric 1-D to know the aquifer location based on the section of medium resistivity value. Then, the geoelectric data was correlated to the borehole drilling data that is Gamma Ray (GR) Log, Spontaneous Potential (SP) Log, Resistivity Log, and the cutting data. Commonly, the most suitable lithology for an aquifer is sandstone because of its good characteristic of permeability and porosity. Logging data result will show the small value of GR log, SP Log lean-ing to the right, and low-value resistivity for indicating the aquifer zone. Based on geoelectric data, the research zone has 3 groups of resistivity value and lithology that are shaly clay-stone and siltstone with low-value resistivity (0-50 ohm.m), sandy claystone, medium sandstone, and coarse sandstone with medium value resistivity (50-150 ohm.m), fine sand-stone, sandy claystone, and andesite with high-value resistivity (> 150ohm.m). The aquifer system in the research area was classied into 3 groups that are aquifer, aquitard, andaquiqlud.

Application of Velocity Variation with Angle (VVA) Method on an Anisotropic Model with Thomsen Delta Anisotropy Parameters Waskito Pranowo; Sonny Winardhi
Jurnal Geofisika Vol 16 No 2 (2018): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Anisotropic properties will influence seismic propagation, for example it will affect wave velocity. One of well-known anisotropi equation for Transversaly Isotropic media is weak anisotropy with Thomsen's notation. Supriyono [2011] tried to estimate all of these variables by using velocity variation with angle (VVA) attribute. This research uses synthetic data, which is CMP Gather to know limitations of VVA attribute, to identify the error values, and to determine the best indicator of anisotropic eect. This research also uses another analysis method, which is grid search inversion to estimate VP0. From this research, Both VVA and grid search invesion still produce signcant error. The effects which will appear because of anisotropic property's presence are hockey-stick and over NMO-stretching.

Identiﬁkasi Reservoir Menggunakan Metode Short Oﬀset Transient Electromagnetic Donny Prasetyo; Muhammad Hasbi Assiddiqy; Warsa Warsa
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.v15i1.400

Metode Short Oﬀset Transient Electromagnetic (SHOTEM) merupakan metode geoﬁsika elektromagnetik domain waktu yang digunakan untuk mendapatkan variasi nilai resistivitas di bawah permukaan tanah sebagai informasi acuan untuk melakukan identiﬁkasi tubuh anomali khususnya reservoir. Selain sinyal hasil pengukuran yang didapatkan sudah bebas dari pengaruh sinyal sumber, metode SHOTEM unggul dari segi jangkauan kedalaman investigasi dan resolusi dibanding menggunakan konﬁgurasi transient electromagnetic (TEM) lainnya. Pada penelitian ini, digunakan data lapangan di 18 titik sounding yang didapat dari penggunaan metode SHOTEM. Beberapa tahapan pemrosesan data yang memanfaatkan sifat gelombang, prinsip statistika, dan pendekatan numerik dilakukan untuk membersihkan data dari noise, lalu dilakukan pemodelan ke depan dan pemodelan inversi satu dimensi menggunakan software IX1D untuk menghasilkan model resistivitas satu dimensi bawah permukaan. Model resistivitas satu dimensi tersebut di interpolasi agar menghasilkan citra variasi resistivitas dua dimensi untuk mengidentiﬁkasi tubuh anomali di bawah permukaan daerah pengukuran data lapangan tersebut. Dari model yang dihasilkan, terdapat anomali resistivitas tinggi yang berasosiasi dengan keberadaan reservoir hidrokarbon di rentang kedalaman 800 – 1000m pada daerah penelitian. Error RMS fungsi objektif pemodelan yang tidak stabil dan sebaran nilai resistivitas yang ekstrem pada 18 model satu dimensi menimbulkan kecenderungan model yang dihasilkan tidak representatif. Hasil tersebut dapat disebabkan data yang masih mengandung noise akibat sistem pengukuran dan noise akibat pengaruh ﬁtur geologi lokal yang belum dikompensasi.

Temporary Seismic Stations Installation and Building Damage Assessment of December 7th, 2016 Earthquake in Pidie Jaya, Aceh, Indonesia Zulfakriza Z.; Andri D. Nugraha; M. Ridwan; Kadek P. Hendrawan; Muksin Umar; Muzli Muzli; Kemal Erbas; Daryono Daryono
Jurnal Geofisika Vol 16 No 1 (2018): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

A signicant Mw 6.5 earthquake occurred in Pidie Jaya, Aceh on December 7th, 2016. The event affected104 people death and more than 1000 people suered injuries due to the rubble of the building. Geologically, the region is composed by of Quaternary alluvial deposits. This is one of factor that amplication occurred in some area. On the other hand, an understanding of the source and mechanism of the earthquake needs to be done. A few days after the earthquake, we deployed 9 seismometers that covered the area of Pidie, Pidie Jaya and Bireuen. This experiment aims to record the aftershock and understanding of earthquake source and mechanism. In addition, we conducted building damage survey to know the pattern of distributionof building damage.

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Home Page

OAI Link

Editorial Team

Contact

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Contact Name Zulfakriza

Contact Email zulfakriza@gmail.com

Phone +6281360729183

Journal Mail Official secretariat@hagi.or.id

Editorial Address Patra Jasa Tower, 18th Floor (Suite 1820), Jl. Gatot Subroto Kav. 32-34, Kuningan Jakarta Selatan

Location Kota adm. jakarta selatan, Dki jakarta INDONESIA

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Contact Name
Zulfakriza

Contact Email
zulfakriza@gmail.com

Phone
+6281360729183

Journal Mail Official
secretariat@hagi.or.id

Editorial Address
Patra Jasa Tower, 18th Floor (Suite 1820), Jl. Gatot Subroto Kav. 32-34, Kuningan Jakarta Selatan

Location
Kota adm. jakarta selatan,

Dki jakarta

INDONESIA