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Zulfakriza
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+6281360729183
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secretariat@hagi.or.id
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INDONESIA
Jurnal Geofisika
ISSN : 0854352     EISSN : 24776084     DOI : https://doi.org/10.36435/jgf
Core Subject : Science,
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.
Articles 5 Documents
Search results for , issue "Vol 18 No 1 (2020): Jurnal Geofisika" : 5 Documents clear
Coulomb Stress Change of Mw 7.5 Palu-Donggala Earthquake, Sulawesi (28 September 2018) Adhi Wibowo; Pepen Supendi; Andri D. Nugraha
Jurnal Geofisika Vol 18 No 1 (2020): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v18i1.423

Abstract

The Mw 7.5 Palu earthquake that occurred in Palu-Central Sulawesi, Indonesia, on September 28, 2018, accompanied by the tsunami and liquefaction caused casualties and building damage in the city of Palu and its surroundings. One month later, a series of earthquakes swarm occurred in Mamasa, West Sulawesi. In this study, coulomb stress were calculated using a half-space elastic model in a square plane which is assumed to be homogeneous isotropy to analyze whether there is a relationship between earthquakes that occur in Palu and earthquakes swam in the coulomb stress field changes. The results show that the area that experienced a stress reduction predominantly towards the north and south of the mainshock hypocenter, while the aftershocks were at an increase in coulomb stress changes, so that the Mamasa earthquakes swarm probably have been triggered by the Palu earthquake.
Analysis of H/V Ratio Curve to Estimate Seismic Hazard Vulnerability in Lombok Island, West Nusa Tenggara, Indonesia Muhammad Randy Caesario Harsuko; Zulfakriza Z.; Andri Dian Nugraha; Muzli Muzli; David Prambudi Sahara; Nanang T Puspito; Yayan M Husni; Billy S Prabowo; Achmad Fajar Narotama Sarjan
Jurnal Geofisika Vol 18 No 1 (2020): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v18i1.432

Abstract

In 2018, Lombok Island was hit by a series of destructive earthquakes. According to Indonesian Meteo- rological, Climatological, and Geophysical Agency data, about 1,973 felt earthquakes (M > 3) which shaken Lombok were recorded during August 2018 with three earthquakes with the largest magnitude of 6.9 Mw, 6.8 Mw, and 6.2 Mw. National Board for Disaster Management reported about 555 deaths, 1,833 people injured, and 186,010 houses damaged as a result of Lombok earthquake on August 5th, 2018. A number of seismometers were placed on Lombok Island from August 3rd, 2018 to October 19th, 2018 to monitor the aftershock events. There are 17 stations that record seismicity in Lombok consisting of 10 broadband sensors and 7 short period sensors. In this study, we used the Horizontal-to-Vertical Spectral Ratio (HVSR) method to analyze the risk of earthquake in the Lombok region. The basic concept of this method is to do a comparison between the horizontal component spectrum and the vertical component spectrum of a wave, where theoretically the particle movement of the horizontal component is greater than the particle movement of the vertical component on soft ground, whereas on the hard ground both components (horizontal and vertical) will be similar. H/V curve obtained from earthquake record- ings (Earthquake Horizontal-to-Vertical Ratio/EHVR) and H/V curve obtained from microtremor recordings (Microtremor Horizontal-to-Vertical Ratio/MHVR) shows good agreement and high correlation. Empirical correction of EMR (Earthquake-to-Microtremor Ratio) managed to decrease the difference of estimation of predominant frequency and amplification factor between EHVR and MHVR. Predominant frequency, amplification, and seismic vulnerability map agree with the geological condition of Lombok Island, where high value of amplification and seismic vulnerability was found on soft and thick ground. This study conclude that the maximum ground acceleration and the construction of the building should also considered when one wants to investigate the effect of an earthquake to the damage occurred, beside the site effects.
Ambient Noise Analysis During Nyepi in Denpasar Using Horizontal-to-Vertical Spectral Ratio (HVSR) Method I Putu Dedy Pratama; Dwi Karyadi Priyanto; Pande Komang Gede Arta Negara
Jurnal Geofisika Vol 18 No 1 (2020): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v18i1.424

Abstract

Nyepi Day is a unique tradition where outdoor human activities stop 24 hours a day. Denpasar City is the region that has the most significant impact on this change because it is the capital province. This study aims to determine the effect of Nyepi on ambient noise in Denpasar on March 25, 2020. We installed a TDS sensor at the Denpasar Geophysics Station for 3x24 hours ie when Nyepi Day, before and after Nyepi as comparative data. The data is processed by the HVSR method to get the value of dominant frequency and amplification factor every hour. Compared to the day before and after Nyepi, the dominant frequency increased during Nyepi and the amplification factor decreased during Nyepi. Seismic vulnerability index value at Nyepi is 24 where there is a decrease of index 3,904 with a day before and after Nyepi. This is showed that Nyepi Day affected ambient noise in Denpasar.
Early Results of Comparison between K-Nearest Neighbor and Artificial Neural Network Method for Facies Estimation Hadyan Pratama; Loris Alif Syahputra; Muhammad Fauzan Albany; Agus Abdullah; Sandy Kurniawan Suhardja; Epo Kusumah; Weny Astuti; Bambang Mujihardi
Jurnal Geofisika Vol 18 No 1 (2020): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v18i1.418

Abstract

Artificial Intelligence method has been widely used recently in many aspects to understand big data. Fundamentally, the purpose of Artificial Intelligence is to solve nonlinear problem. Most methods are trying to optimize an output from one or many inputs parameter by identifying any potential patterns that fit or using a statistical data. In Oil & Gas industry, one of the main challenges that can be solved by Artificial Intelligence is estimating facies from well log or seismic data. The main scope of this study is estimating lithofacies by analyzing well logs input using two different methods, K-Nearest Neighbor (KNN) and Artificial Neural Network (ANN). We employed various well log data such as gamma-ray, resistivity, neutron density porosity, and photoelectric effect from well log data at Panoma Council Grove Field, South West Kansas, United States. This study shows that using optimized parameters, KNN method faster than ANN method but, ANN give result better than KNN. Nevertheless, despite the fact this research could estimate lithologies, many aspect should be considered in order to reach optimum result such as insights from geological regional models.
Analysis and Zonation of Land Vulnerability Areas in Pekon Karangrejo Ulubelu Tanggamus Using Microzonation Method Eko Rananda; Lintang Prabowo; Arief Putih Prabowo; Syamsurijal Rasimeng; Ida Bagus Suananda Yogi
Jurnal Geofisika Vol 18 No 1 (2020): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v18i1.420

Abstract

Abstract.Ulubelu Tanggamus is an area that have geothermal energy potential. This region consists of a geological structure in the form of graben and reverse fault formed between Mount Rendingan and Mount Kukusan. Identifications that can be done include surveys to map soil characteristics in shaking responses using microzonation methods. This study aims to analyze the values ​​of dominant frequency, dominant period, Vs30 and amplification. The stages of the research carried out are processing data to obtain dominant frequency, calculating the value of the dominant period, calculating the value of Vs30 and the amplification value, and making a map of the soil vulnerability of the UlubeluTanggamus area. Based on the distribution of the dominant frequency values, the UlubeluTanggamus geothermal area is dominated by a dominant Frequency (F0) >0.5Hz which is expected to be a very thick surface thickness of sediments more than 30m. The distribution of the dominant period value obtained is (T0)>1 where the character of the sedimentary rock type is very soft consisting of alluvial material formed from sedimentation of deltas, top soil, and mud. The distribution of the Vs30 value is dominated by the value of 100 <Vs30<200 and obtains an amplification value of 2<A0<6 times where the area is an area with a moderate risk category to the danger of soil vulnerability.

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