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1	Biophysics and Medical Physics	ABS-4
Radiobiological Analysis of Radioiodine Absorption in Thyroid Cancer Therapy Yuanita Puspita Dewi Sudarso*, Rena Widita Department of Physics, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia Abstract Thyroid cancer therapy using I-131 has already used widely to help ablate thyroid remnants, but many patients still not convinced whether this therapy really ablate thyroid or not and their distribution in the body, also about the effect of metabolic process on decreasing the exposure rate of the body so that patient can go home early. The other common problem for this therapy is limited isolation room in the hospital which leads to long queue of patients. By exposure rate of the body and urine of the patient, will be determined the uptake percentage, absorbed dose, absorption rate, and washing out percentage that helped to determine the probability of radioiodine absorption in thyroid compared to other organs and effect of metabolic process on decreasing the body exposure rate of the patient. This research will be focused to prove that this therapy indeed being absorbed more in thyroid rather in other organs and by increasing the metabolic activity, the exposure rate of the patient will decrease faster which means that the treatment going faster and reduce the queue of this therapy. Keywords: Metabolism- Radioiodine- Radioiodine Therapy Share Link | Plain Format | Corresponding Author (Yuanita Puspita Dewi Sudarso)

2	Biophysics and Medical Physics	ABS-8
Evaluation of Pupillary Distance (PD) Measurement using Smartphone-based Pupilometer Hanna Nurul Husna (a*)- Naida Fitriani (b) (a), (b) Department of Optometry, STIKes Bakti Tunas Husada *hannanurulhusna[at]stikes-bth.ac.id Abstract Measurement of the pupillary distance (PD) is one of the important steps of the spectacles-making process. PD measurement can be done using the PD Ruler, Auto-refractometer, and smartphones^ apps. The study aims to evaluated PD measurement apps (Pupil Distance Meter Pro from Vistech Project, PD Pupil Distance for Eye Glasses and VR Headset from Glassify Me, and The Ultimate PD Rule) and compared them with Auto-refractometer as the gold standard. A total of 39 students (age 19-22) were involved in this study. The result of this study indicated that there was no difference between the measurement of the PD using the Glassify Me app and the Auto-refractometer (p = 0.48). However, there was a mean difference of 0.2 mm between them. It could be concluded that the Glassify Me app has the best accuracy compared to other apps. This app was recommended to be used as an alternative to PD measurement. Keywords: pupillary distance- smartphone- pupilometer Share Link | Plain Format | Corresponding Author (Hanna Nurul Husna)

3	Biophysics and Medical Physics	ABS-113
Statistical analysis of quantitative electrocardiographic signals with standard limb leads: Influences of gel use, subject positions, and electrodes configurations Khotimah, S.N., Wahyuni, F.S., Viridi, S. and Haryanto, F. Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung Jalan Ganesha 10, Bandung 40132, Indonesia Abstract Electrocardiogram is a recording of the heart^s electrical activity that provides helpful information of cardio electrophysiological process. One cycle of cardiac contraction and relaxation produces the basic waves that consists of a P wave (atrial depolarization), a QRS complex (ventricular depolarization), and a T wave (ventricular repolarization). In this study, the quantitative electrocardiographic signals from six adult female subjects were measured using Cobra4 Electrophysiology with standard limb (extremity) leads. The correlation between Electrocardiographic signals during measurement on each subject was analysed statistically. We investigate the influences of some treatments: the use of gel in the measurement process, the position of the subject (lying or sitting), and the exchange positions of exploring and indifferent electrodes. The data was analyzed statistically for parameters duration and amplitude of the electrocardiographic signals. Keywords: electrocardiographic signals, statistical methods, position of the subject ,electrodes configurations Share Link | Plain Format | Corresponding Author (Siti Nurul Khotimah)

4	Biophysics and Medical Physics	ABS-118
Monte Carlo Simulation of electron production in target material Linac 6, 10, and 18 MV photon beam Sitti Yani(a), Indra Budiansah(b), Mohamad Fahdillah Rhani(c), and Freddy Haryanto(d) (a) Department of Physics, Faculty of Mathematics and Natural Sciences, Bogor Agricultural University, Indonesia (b) SMA Darul Hikam Bandung, Indonesia (c) Department of Radiology, Kathleen Kilgour Center, New Zealand (d) (a) Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Indonesia Abstract Target is one of important component in a linear accelerator (Linac). Target materials depend on the energy of Linac so that they have different spectrum produced. In this study, the spectrum characteristic of target material for some Linacs using Monte Carlo codes is investigated. The target material simulated was collected from Varian Medical System. The simulation was carried out on two different Monte Carlo codes namely PHITS and EGSnrc. In the simulation process, the cut-off energy of electron and photon are set in the same value at 0.521 MeV and 0.01 MeV, respectively. The SLAB geometry is implemented to model the target. The spectrum of photon and electron was collected 0.1 cm from the end of target. The deviation of electron and photon spectrum collected from PHITS and EGSnrc was calculated in the end of simulation. The results show that the spectrum of photon and electron from PHITS and EGSnrc have the same trend with deviation less than 5%. The spectrum calculation in PHITS was more efficient than EGSnrc. Keywords: Monte Carlo, EGSnrc, PHITS, Linac Share Link | Plain Format | Corresponding Author (Sitti Yani)

5	Biophysics and Medical Physics	ABS-151
Electroencephalography Signal Power Spectral Density from Measurements in Room With and Without Faraday Cage: A Comparative Study Galih Restu Fardian Suwandi (a*), Siti Nurul Khotimah (a), Freddy Haryanto (a), Suprijadi (b) (a) Nuclear Physics and Biophysics Research Group, Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung Jl. Ganesha no.10 Bandung 40312 - Indonesia *galih[at]fi.itb.ac.id (b) Instrumentation and Computation Physics Research Group, Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung Jl. Ganesha no.10 Bandung 40312 - Indonesia Abstract Electroencephalography (EEG) is a method for recording the brain^s electrical activity through electrodes placed on the scalp^s surface. This EEG has its problem, namely signal interference from outside the system or artifacts. Efforts to eliminate this signal interference can be made in various ways, including handling signal sources outside the system or removing interference signals during the EEG signal processing process. One way is to isolate the measurement room from signal interference using a Faraday cage. In this study, we will compare the results of EEG signal processing in the form of power spectral density (PSD) from measurements in a room without a Faraday cage and a room with a Faraday cage. We find that the average value of the change in PSD from the measurement results in the two rooms had a level of difference that varied between 0.7%-66%. The location of the electrodes that have a high difference value is the frontal and parietal areas. Keywords: brainwaves, electroencephalography, Faraday cage, power spectral density Share Link | Plain Format | Corresponding Author (Galih Restu Fardian Suwandi)

6	Biophysics and Medical Physics	ABS-181
Developing Highly Porous Borate Glass Microspheres via a Single-Stage Flame Spheroidisation Process Nur Aisyah Nuzulia (a,b), Md Towhidul Islam (c,d), Angga Saputra (b), Toto Sudiro (e), Gerald Ensang Timuda (e), Terry Mart (a*), Yessie Widya Sari (b), and Ifty Ahmed (c) a) Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia * terry.mart[at]sci.ui.ac.id b) Department of Physics, Faculty of Mathematics and Natural Sciences, IPB University c) Advanced Materials Research Group, Faculty of Engineering, University of Nottingham d) Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Noakhali Science and Technology University, Noakhali-3814, Bangladesh e)Research Center for Physics, Indonesian Institute of Sciences, Indonesia Abstract Porous bioactive glass microspheres have been developed for biomedical application due to their excellent bioactivity, osteoinductivity and osteoconductivity properties. The spherical particles offer a larger surface area over irregular shaped particles. In addition, porous spherical particles possess greater loading efficiency for incorporating drugs and biological molecules and having good flow properties for facilitating minimally invasive injection. This paper presents the manufacture of B53P4 glass microspheres (solid and porous) by using a flame spheroidisation process and investigates the effect of various acetylene and oxygen gas ratios on the morphological changes of B53P4 glass microspheres. The irregular shaped B53P4 glass particles with starting particle size ranges of 63 up to 125 micrometres were used as feed and delivered to a hot flame to prepare microspheres. In addition, calcium carbonate was utilised as a porogen for the manufacture of B53P4 porous glass microspheres via single-stage flame spheroidisation process. Solid and porous glass microspheres were successfully produced in various acetylene and oxygen gas ratios of 3 to 3, 4 to 7, 5 to 7 and 6 to 7 with the mean particle size range of 73 up to 105 micrometres. Moreover, the average pore sizes of 6 micrometres and 9 micrometres were obtained by using 5 to 7 and 6 to 7 gas ratios, respectively. Therefore, single-stage flame spheroidisation process is a promising method for production of porous borate glass microspheres. Keywords: acetylene, oxygen, scanning electron microscope Share Link | Plain Format | Corresponding Author (Nur Aisyah Nuzulia)

7	Earth and Planetary Sciences	ABS-3
Simple Forward Calculation Study for Anomaly Response Simulation and Geomagnetic Data Transformation in Karangsambung Area Waskito Aji , Eko Januari Wahyudi (*), Stephen Daniel Simanjuntak, Samuel Belia Geophysical Engineering, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia *ekojw[at]gf.itb.ac.id Abstract A geomagnetic survey aims to obtain a model related to geological conditions based on the magnetic properties of the rock. Forward modeling techniques can estimate the anomalies that will be observed based on anomalous bodies below the surface. The rectangular prism body forward modeling approach can approximate a complex anomaly body to be a prism group, thus simplifying the computational process of forward modeling. In this research, a program for computing the forward calculation of magnetic data with rectangular prism approach is arranged. The program is applied to perform forward modeling of the Karangsambung geological conceptual model. Based on the modeling carried out, the magnetic anomaly range in the Karangsambung area was obtained, namely -3200 nT to 2700 nT with the smallest wavelengths based on the simulation results shown in the range of 200 meters. In addition, the forward modeling program is also used to transform geomagnetic data in the Karangsambung area. The transformations applied are the reduction to the poles and the upward continuation transformation by utilizing the equivalent source technique. Based on the transformation result, it can be interpreted that the area of the intrusion rock in Karangsambung is indicated by a magnetic anomaly value of up to 400 nT. While the area of sedimentary rocks, especially the Karangsambung Formation, is shown by a low magnetic anomaly value reaching -400 nT. Keywords: geomagnetic- forward modeling- karangsambung Share Link | Plain Format | Corresponding Author (Waskito Aji)

8	Earth and Planetary Sciences	ABS-16
Velocity Dispersion Attribute in Carbonate Reservoir Mokhammad Puput Erlangga (a*,b), Sigit Sukmono (b), Wahyu Triyoso (b), Teuku Abdullah Sanny (b), Asido Saputra Sigalingging (a,b), Egie Wijaksono (c) a) Geophysical Engineering Department, Institut Teknologi Sumatera Jl. Terusan Ryacudu, Way Hui, Kecamatan Jati Agung, Lampung Selatan 35365 *mokhammad.erlangga[at]tg.itera.ac.id b) Geophysical Engineering Department, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia c) Research and Development Centre For Oil and Gas Technology Jl. Ciledug Raya No.Kavling 109, RT.7/RW.5, Cipulir, Kec. Kby. Lama, Kota Jakarta Selatan, Daerah Khusus Ibukota Jakarta 12230 Abstract Detection of the presence of saturated hydrocarbons in pores or rock fractures is a major problem in the field of exploration geophysics which is interesting to study. Some of the fluid saturation indicators were originally derived from the Zoepprit equation. However, the indicator that is derived from the linearization of the reflection coefficient is not influenced by frequency. In fact, frequency is a physical quantity that is very sensitive to the presence of fluid in a pore or rock fracture. Seismic waves will experience attenuation and dispersion when propagating through a porous medium or gas-saturated fractures. Therefore, we need an indicator whose value is influenced by changes in the frequency of seismic waves. This indicator is an attribute of the velocity dispersion. In previous studies, the velocity dispersion attribute was used to detect the fluid content of gas in sandstone. Based on this research, it turns out that it shows effective results in mapping the presence of saturated gas zones in the carbonate pores. In the end, the results of this study will be able to map the presence of saturated gas zones in carbonate reservoir. Keywords: amplitude, frequency, velocity, dispersion, saturation Share Link | Plain Format | Corresponding Author (Mokhammad Puput Erlangga)

9	Earth and Planetary Sciences	ABS-19
Gravity Forward and Inversion Modelling in Improving the Geology Model of the Flank Volcanic Structure Agus Laesanpura(1), Benyamin Oozatulo Telaumbanua,(2) Toni Rahadinata(3), Gestin Mey Ekawati(2), Asep Suginato(3) 1) Institut Teknologi Bandung, JL. Ganesha 10 Bandung 2) Institut Teknologi Sumatera, JL. Terusan Ryacudu, Lampung 3) PSDMBP - ESDM, Jl. Soekarno Hatta No. 444 Bandung - 40254 Abstract Cross-sections of volcanic structures are usually constructing based on existing data on surface rocks. The detailed subsurface structure is inaccessible due to a limitation of general principles- hence, the accuracy is less accurate. The geophysical data obtained through surface gravity measurements will improve this phenomenon based on the response of density changes to the forward or reverse modelling of underground structures. Joint interpretation will improve the subsurface model and apply to the subsurface phenomena in volcano deposits experiencing downdraft fault. Gravity data acquire is 286 points in 16 x 24 square km area. An anomaly study will focus on near surface phenomena, where modelling show needs an improvement for inversion through refining the grid. Furthermore, forward modelling makes the model more realistic. Result show, the fault as volcanic fault, geology throws reach 0.5 km not seen in geology section, and density variation show 0.3 gr/cc from the surrounding. This variation of density is due to the varying of pyroclastic rock. Fumaroles in the surface may interpreting as the pathway of water percolation from the peak through flank structure. Water is flowing inside volcanic deposits and fault line is the end points of meteoric water reaching to surface. Keywords: Gravity, volcano Share Link | Plain Format | Corresponding Author (Agus Laesanpura)

10	Earth and Planetary Sciences	ABS-20
Temporal variation in crustal shear wave splitting associated with a moderate earthquake around Nias Island, Indonesia Syuhada Syuhada, Titi Anggono, Febty Febriani, Jauhari Arifin, Cinantya Nirmala Dewi, Aditya Dwi Prasetio, Mohammad Hasib Research Centre for Physics - National Research and Innovation Agency Republic of Indonesia (BRIN) Abstract We investigate temporal variation in shear wave splitting parameters of local earthquakes around Nias Island, northern part of Sumatran forearc. We analyse a total of 79 high-quality splitting measurements recorded at a GEOFON seismic station (GSI) from 2009-2015. We observe that there is no clear time variation in fast polarization of the splitting waves. On the other hand, an increase in delay time of the splitting waves is found prior to a medium earthquake that occurred around the island on August, 2010. Therefore, we suggest that this temporal change may be related to the change in crack geometry of rocks following the accumulation of the stress in the crust before the earthquake occurred. Keywords: Temporal variation- shear wave splitting- Nias Island Share Link | Plain Format | Corresponding Author (Syuhada Syuhada)

11	Earth and Planetary Sciences	ABS-25
Creating A Conversion Table Departure Time To Prayer Time on The Airplane Endi Hari Purwanto Pusat Riset dan Pengembnagan SDM, Badan Standardisasi Nasional (BSN) Abstract Abstract is submitted as file Keywords: standard conversion table time, prayer time, astronomical time, and validationstandard conversion table time, prayer time, astronomical time, and validation Share Link | Plain Format | Corresponding Author (Endi Hari Purwanto)

12	Earth and Planetary Sciences	ABS-30
HYPOCENTER DETERMINATION USING A NON-LINEAR METHOD IN BALI, LOMBOK AND NUSA TENGGARA REGIONS, INDONESIA: PRELIMINARY RESULT Fajar Rachmadi Priyambada(1,3), Andri Dian Nugraha(2), Pepen Supendi(3) 1) Master Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung 40132, Indonesia 2) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung 40132, Indonesia 3) Agency for Meteorology, Climatology, and Geophysics (BMKG), Jakarta 10720, Indonesia Abstract Bali, Lombok, and Nusa Tenggara are the region in the south of the Indonesia Archipelago. This region has relatively high seismicity due to subduction activity and faulting. The first step of the tomography study for inferring the geometry structure beneath Bali, Lombok, and Nusa Tenggara is to conduct precise hypocenter location. In this study, we used waveform data from the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG), which the study area is between 112 - 128 E and 4 - 13 S. Our preliminary results, we have re-picked 7967 P-wave and 3254 S-wave arrival times for 933 events in the time period from January to March 2019. The non-linear method was conducted using the oct-tree sampling algorithm from the NonLinLoc program to determine the hypocenters location. We also compared the results with BMKG catalog data. Our results show better clustering earthquakes with RMS error mostly close to zero and represent the geological structure in this region. The results show a shift in the location of the epicenters between 0.1 km to 1000 km, while for the focus depth between 0.006 - 500 km, with the azimuth shift being dominated to the northeast and southwest. The future and ongoing works, we will conduct a tomography study to imaging 3-D seismic velocity models beneath Bali, Lombok, and Nusa Tenggara using the fast marching method. Keywords: Bali, Lombok, Nusa Tenggara, non-linear method, hypocenter, seismicity Share Link | Plain Format | Corresponding Author (Fajar Rachmadi Priyambada)

13	Earth and Planetary Sciences	ABS-41
Terrain Correction in Gravity Data Processing using Hybrid Land Survey and Shuttle Radar Topography Mission Digital Elevation Model: A Case Study in Mount Pandan, Indonesia Indra Gunawan(*), Eko Januari Wahyudi, Susanti Alawiyah Applied and Exploration Geophysics Research Group, Institut Teknologi Bandung, Jalan Ganesa No.10, Bandung 40132, Indonesia *gunawan[at]geoph.itb.ac.id Abstract A clean corrected complete Bouger anomaly would perform reasonable geological subsurface interpretation. As a part of the processing phase, the terrain correction has a significant influence. Since the terrain correction entangles a vast area, it isn^t easy to fulfill with land survey. Our study aimed to apply a shuttle radar topography mission digital elevation model (SRTM DEM) in addition to land survey data to overcome a satisfactory terrain correction. We have applied the SRTM data to calculate the terrain correction for the outer zone (i.e., D to M) using the Hammer method. In Mount Pandan, Indonesia, we have set this method to generate a complete Bouguer anomaly as a case study. The terrain correction in the outer zone has corrected the gravity anomaly up to 16 mGal. The result shows that the hybrid elevation data may provide sufficient terrain correction in gravity data processing for practical geological subsurface interpretation. Keywords: gravity- terrain correction- bouguer anomaly- SRTM- digital elevation model Share Link | Plain Format | Corresponding Author (Indra Gunawan)

14	Earth and Planetary Sciences	ABS-53
Preliminary Result of Rayleigh Wave Tomography beneath Jailolo Volcanic Complex, North Moluccas, Indonesia using Ambient Noise Aprilia Nur Vita(a*)(c), Zulfakriza(b), Andri Dian Nugraha(b) Agustya Adi Martha(c), Supriyanto Rohadi(c), Nova Heryandoko(c), Claus Milkerreit(d) (a)Master Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Bandung, Indonesia. *aprilia.nurvita[at]gmail.com (b)Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia. (c)Agency of Meteorology, Climatology, and Geophysics (BMKG), Jakarta, Indonesia. (d)German Research Centre for Geoscience (GFZ), Postdam, German. Abstract Abstract. In November 2015 to February 2016, seismic swarm activity occurred around Jailolo volcano, a long dormant and few studied of volcano that located on Halmahera Island, North Moluccas, Indonesia. We perform seismic ambient noise tomography method to delineate the sub surface seismic structure beneath Jailolo volcanic complex. We use vertical component of seismogram data retrieved from 29 temporary short-period seismic stations of 7G Seismic Network in January to March 2017 observation. The 7G Seismic Network was collaboration research between Indonesia Agency of Meteorology, Climatology and Geophysics (BMKG), Indonesia and German Research Centre for Geoscience (GFZ). We cross correlated vertical component of pair stations to estimated Green^s function of Rayleigh wave. More than 350 of group velocity were estimated. We measure the dispersion characteristic of Rayleigh wave group velocity by applied frequency time analysis (FTAN) technique. We compare Green Function and the dispersion curve by applied different bandpass filter. The Green Function of Rayleigh wave is clearly seen in causal and/or acausal part by applied 0.01-0.5 Hz band-pass filter and then dispersion curve is picked within 2-10 s. The Rayleigh group velocities average is 0.6-0.9 km/s Keywords: Jailolo, Halmahera, Indonesia, swarm earthquake, Rayleigh wave, ambient noise tomography Share Link | Plain Format | Corresponding Author (Aprilia Nur Vita)

15	Earth and Planetary Sciences	ABS-70
Focal Mechanism Inversion on the Aftershock Sequence of the October 25th, 2010 Mw 7.8 Mentawai Earthquake: A Preliminary Result Gatut Daniarsyad (a, c*), Afnimar (b) a) Master Program of Earth Sciences, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia b) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Bandung, Indonesia c) Agency for Meteorology Climatology and Geophysics (BMKG), Jakarta, Indonesia *lp.daniarsyad[at]gmail.com Abstract A Mw 7.8 tsunami earthquake ruptured the shallow part of the Mentawai megathrust on 25 October 2010 and generated large tsunami that hit the Mentawai Islands. The earthquake continued a partial rupture sequence of the 2007 Mw 8.5 and 7.9 Bengkulu earthquake and the 2008 Mw 7.2 North Pagai earthquake. The aftershock activity gives the opportunity to investigate the geometry of the subduction interface which is critical to understand the propagation and termination of a large earthquake. However, it is necessary to have a precise location and mechanism of the aftershock distribution to clearly image the fault geometry. In this preliminary study, we have applied the generalized Cut-and-Paste (gCAP) focal mechanism inversion method to 20 aftershocks (M > 4.9) of the 2010 Mentawai earthquake. The seismic waveforms recorded by the BMKG broadband seismic network on the regional distance were used in the inversion and successfully obtained 10 focal mechanisms more than that provided in the GCMT catalog. The gCAP inversion by using teleseismic stations was then performed to validate the focal mechanism solution and its centroid depth. The result exhibits a distinctly different thrust and normal faulting aftershocks activity. The thrust faulting aftershocks are mainly distributed in the downdip of the Mentawai 2010 mainshock rupture, indicating the stresses that have not been released during the mainshock. In the shallow region near the trench, the aftershocks are dominated by a normal faulting mechanism which shows the tensional stress caused by the bending of the subducted plate. Keywords: 2010 Mentawai earthquake, aftershock, focal mechanism, fault geometry Share Link | Plain Format | Corresponding Author (Gatut Daniarsyad)

16	Earth and Planetary Sciences	ABS-74
Evaluation of Atmospheric Correction Methods of Sentinel-2 for Monitoring Paddy Rice Growth in Cianjur and Klaten Districts Fadila Muchsin(1a), Supriyatna(2), Adhi Harmoko(3), Indah Prasasti(4) 1,2,3) Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Indonesia a fadila.muchsin[at]lapan.go.id 4) Remote Sensing Application Center - LAPAN, Indonesia Abstract Atmospheric correction is a critical pre-processing step required in quantitative remote sensing applications such as extraction of biophysical variables and multi-temporal analysis. The objective of this study was to evaluate surface reflectance of atmospheric correction methods base on scene-based empirical namely Dark Object Subtraction (DOS) and the radiative transfer methods namely the Second Simulation of Satellite Signal in the Solar Spectrum (6S). We applied these methods to Sentinel-2 images above rice fields in Cianjur and Klaten Regency, and compared surface reflectance from atmospheric correction methods with ground measured reflectance base on spectral response and vegetation indices (NDVI, EVI, SAVI and MSAVI). For that purpose, generative phase of rice growth was analysed by using statistical analysis. The result showed that the 6S method has better accuracy than DOS. Keywords: Atmospheric correction, Sentinel-2, Rice growth phases, Statistical analysis, Vegetation indices Share Link | Plain Format | Corresponding Author (Fadila Muchsin)

17	Earth and Planetary Sciences	ABS-82
Relative Seismic Velocity Change Analysis Using Ambient Seismic Noise on Agung Volcano, Bali, Indonesia Lalu Iqbal Tawakkal Akbar (a*), Zulfakriza (b,d), Shindy Rosalia (b), Andri Dian Nugraha (b,d), David Prambudi Sahara (b), Sri Widiyantoro (b), Devy Kamil Syahbana (c) a) Undergraduate Program of Geophysical Engineering Program, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Indonesia *laluakbar[at]students.itb.ac.id b) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Indonesia c) Center for Volcanology and Geological Hazard Mitigation, Geological Agency, Bandung, Indonesia d) Center for Earthquake Science and Technology, Research Center for Disaster Mitigation, Institut Teknologi Bandung, Bandung, Indonesia Abstract Agung volcano is one of the active volcanoes in Bali, Indonesia. According to Center for Volcanology and Geological Hazard Mitigation of Indonesia (CVGHM), Agung volcano erupted in November 2017, after dormant for more than 50 years. Intriguingly, the eruption phase showed a significant increase in seismic activity about two months before (seismic crisis) which then decreased gradually until finally erupted on 21 November 2017. To examine the mechanism of Agung^s magma activity against eruptions, we calculated the relative seismic velocity changes using the cross correlation of ambient seismic noise. Based on the velocity changes obtained, we interpreted how the medium changes caused by stress perturbations in the medium, before and after the eruption. Although it varies spatially, we identify a zone of velocity change with a negative trend between Agung-Batur before the eruption which then increasingly recorded until the eruption. We interpret this as fracture growth due to magma migration towards Agung. The migration also produced the increase in velocity surrounds the volcano that may be related to an increase pressure in the shallow magma reservoir. Furthermore, the eruption caused a significant deformation in volcanic edifice affects the velocity change trend being deceased and fluctuated. Keywords: 2017 Agung eruption- ambient seismic noise- relative seismic velocity change Share Link | Plain Format | Corresponding Author (Lalu Iqbal Tawakkal Akbar)

18	Earth and Planetary Sciences	ABS-85
Study to explore the use of Quality Factor of Body Waves (S waves) as a tool to investigate the soil liquefaction potential G Handayani1 and A F Hariawan1 1Laboratory of Earth Physics Bandung Institute of Technology Abstract Abstract. Liquefaction events occur in deposits of saturated loose sand. Due to the incompressible nature of water, the pore water pressure rises dramatically. Built-up pressure pushes sand particles so that the effective stress between particles becomes zero. Or in other words, these sand particles do not touch each other in the water. So these sand particles are now ^swimming^ in water. These sand deposits behave like water, can flow, and do not have shear strength like normal soil. Not having shear strength means that this soil does not have the carrying capacity of the regular soil against loads above the ground such as buildings etc. This research investigates the possibility of using the Q (quality) factor of seismic waves to estimate the potential liquefaction of soil deposits. We employ Ottawa sand in the laboratory and apply various vibrations using small shaking tables. The results promise of possibilities of using the Q (quality) factor to estimate potential liquefaction. Keywords: Liquefaction soils shaking table Q factor S waves Share Link | Plain Format | Corresponding Author (Gunawan Handayani)

19	Earth and Planetary Sciences	ABS-88
Estimation of Ground Shear Strain using Horizontal to Vertical Spectral Ratio (HVSR) in Bandung Region, West Java, Indonesia Faisal Mamonto (a*), Zulfakriza (b,c), Andri Dian Nugraha (b,c) a) Master Program of Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia *mamonto.faisal[at]gmail.com b) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia c) Center for Earthquake Science and Technology, Institut Teknologi Bandung, Bandung, Indonesia Abstract Bandung region, West Java, Indonesia is a basin area that consist of soft sedimentary profiles and lies on active tectonic zone. This condition probably has the potential for strengthening ground shaking due to vibrations caused by earthquake events in Bandung region. We applied the Horizontal to Vertical Spectral Ratio (HVSR) microtremor method to determine the dynamic response of ground shear strain. We used 51 temporary seismic station in research collaboration between ITB and Australian National University in 2014. This study used 2 hours length of waveform at night recording (20.00 to 23.00 local time) to obtain the HVSR curve. It allows us to estimate the dominant frequency and maximum amplification factor. Then, we estimate dominant period values, earthquake vulnerability index and peak ground acceleration (PGA) based on dominant frequency and the maximum amplification factor and calculate the ground shear strain (GSS). We found the range of number of GSS are \(1\times10^{-5}\) to \(13,3\times10^{-3}\). We interpret that the high number of GSS \(13,3\times10^{-3}\) correspond to weak zone of soil characteristic and possible to be cracks or subsidence. The areas that show high value of GSS are Solokan Jeruk, Ciparay and Majalaya. Keywords: Microzonation, HVSR, GSS, Bandung Basin Share Link | Plain Format | Corresponding Author (Faisal Mamonto)

20	Earth and Planetary Sciences	ABS-90
Petrophysical Characterizations and Shale Distribution Analysis of Kissenda Reservoir Sands, Gabon Nadhiya Pradhanitasari Geophysical Engineering, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia Abstract A gas field in western Gabon is penetrated by an exploration site N field with a major fault dividing the well locations. The upthrown block and the downthrown block have different characterization based on the history of Gabon Basin located in Equatorial West Africa, as part of the salt basin complex. In addition to major fault separating the blocks, four wells are selected in this study to identify each block. Petrophysical properties was undertaken by using wireline logs to generate each well composite. These properties include shale volume, total porosities, water saturation and permeability. The presence of shale in sandstone reservoir can affect the producibility rate of the reservoir. Shale volume and density porosity are cross-plotted using the Thomas-Stieber method to determine the shale distribution of both blocks, including the distribution types of laminar shale, dispersed shale and structural shale. Based on this method, the upthrown block has relatively small grain diameters with mostly laminar-dispersed shale distributions, while in downthrown block the grain diameters are four times larger with more dynamic shale distributions. Keywords: petrophysics, Thomas-Stieber method, shale distribution Share Link | Plain Format | Corresponding Author (Nadhiya Pradhanitasari)

21	Earth and Planetary Sciences	ABS-91
A Preliminary Result of Seismic Hazard Analysis in Eastern Part of Bali Island, Indonesia Imam Catur Priambodo (1,2*), Zulfakriza (3,4), Andri Dian Nugraha (3,4), Akhmad Solikhin (2), Athanasius Cipta (2), Martanto (1,2), Ardianto (1) 1) Master Program of Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia. *icap.711[at]gmail.com 2) Geological Agency, Bandung, Indonesia. 3) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia. 4) Center for Earthquake Science and Technology, Institut Teknologi Bandung Abstract Bali Island is one of the main tourist destinations in Indonesia. However, Bali Island is also prone to earthquakes, as evidenced by several historical destructive earthquakes, especially in the eastern part of Bali. A probabilistic seismic hazard modelling is undertaken to analyse the earthquake hazard, as well as studying the contribution of local geological conditions to earthquake ground motion. We use seismic waveforms retrieved from 23 temporary seismic stations across the eastern part of Bali Island from December 2018 to June 2019 and 5 permanent seismic stations around Mount Agung and Batur. The recording data were processed using the Horizontal to Vertical Spectral Ratio (HVSR) method. Our preliminary result shows local geological conditions for each station, represented by the value of the average shear-wave velocity on rocks to a depth of 30 meters (Vs30) and the total thickness of sediments above the bedrock (basin depth). These initial results will then be developed as site parameter input for probabilistic seismic hazard analysis in the eastern part of Bali. Keywords: Bali, earthquake ground shaking, site amplification, seismic hazard analysis Share Link | Plain Format | Corresponding Author (Imam Catur Priambodo)

22	Earth and Planetary Sciences	ABS-92
Gravity data processing of field camp geophysics in Karangsambung (2005-2019) Eko Januari Wahyudi, Agus Laesanpura, dan Waskito Aji ITB Abstract Gravity data was collected from a previous survey in Karangsambung 2005-2019 (before the restriction of field camp activities due to the Covid-19 pandemic). Luk-Ulo Melange Complex in the Karangsambung area has been the subject of local and regional studies for geoscience students due to the interesting exposure of outcrops that have been interpreted as product of subduction (the Indo-Australian plate under the Eurasian plate in the Late Cretaceous to Early Paleocene time). The data for this gravimetric study based on 2592 observations over an area of inside (9.1 x 9.1) square kilometers. The gravity data were observed by students in the field camps for several years and then we compile. In this work we present simple data processing and simple calculation for modeling. The Bouguer anomaly map was processed using a density estimate of 2.3125 g/cc for slab-Bouguer and terrain correction/reduction. The residual anomaly map was obtained by simple calculation of trend surface analysis (second order polynomial order). The inverse model was calculated using a simple algorithm for 2.5D and the program was built by accomodate topographic variations in the study area. Slice sections (SW-NE) of residual anomalies with a length of more than 8 km were inverted to obtain the contrast density distribution as a subsurface model. The subsurface images can then be analyzed and correlated with geological surface maps in the study area. The work in this paper is mainly presented as an ilustration of simple data processing and inverse modeling, so that the outcomes of this work are: (1) Bouguer anomaly map, (2) residual anomaly map, and (3) contrast density distribution as SW-NE section in the Karangsambung area. The value of the Bouguer anomaly map from this study is in the range of 88 to 112 mGal, and the value of the residual anomaly map is in the range of -12 to 10 mGal. The contrast density distribution from the inverse model in this study is in the range of -0.3 to 0.6 g/cc. Keywords: Gravity- Processing- Inverse Modeling- Karangsambung Share Link | Plain Format | Corresponding Author (Eko Januari Wahyudi)

23	Earth and Planetary Sciences	ABS-94
Measurement of multi-stage triaxial compression test and static elastic parameters of shale samples from the Talangakar formation for a feasibility study of shale gas in the South Palembang sub-basin, South Sumatra basin Dwi Tunggal Adi Prayanto (a), Edy Sunardi (b), Bagus E.B.Nurhandoko(c) (a) UTC Pertamina, (b) Padjadjaran University, (c) Institut Teknologi Bandung Abstract Shale gas is an unconventional gas source that has great potential to be developed and produced in the future. One area that has great potential in Indonesia is in the South Sumatra basin. For good hydrofracturing planning, we used samples of core rock specimens from field well B in the Talangakar formation at a depth of 2289 m with shale lithology located within the South Palembang sub-basin in the South Sumatra basin. We tested the sample by multi-stage triaxial (MST). MST is a compression test that requires only one rock specimen to be tested in three cycle stages with different confined pressures. From this test, the curve of Stress-Strain, yield point, elastic zone and plastic zone is obtained. Then it can also be generated Mohr-Coulomb curve, elastic parameters, i.e: Young^s modulus, Poisson^s ratio, etc. The results of this measurement are also useful for predicting the minimum horizontal stress which is very important in the design of hydraulic fracturing in shale gas. Key words : Shale gas, Talang Akar shale, Hydraulic fracturing, multi stage triaxial, yield point, elastic zone, plastic zone, Mohr Coulomb Keywords: Shale gas, Talang Akar shale, Hydraulic fracturing, multi stage triaxial, yield point, elastic zone, plastic zone, Mohr Coulomb Share Link | Plain Format | Corresponding Author (Dwi Tunggal Adi Prayanto)

24	Earth and Planetary Sciences	ABS-96
Mapping of Peak Ground Acceleration (PGA) Values using the Donovan Model for Sumatra Tati Zera, Ai Rahmi Fauziah, Akbar Ramadhani, M. Nafian Physics, Faculty of Science and Technology, Syarif HIdayatullah State Islamic University, Jakarta. Abstract Abstract. The island of Sumatra is characterized by three tectonic systems, which are sequentially from west to east consisting of an oblique subduction zone with gentle subduction angles, the Mentawai fault, and the Sumatran large fault zone (Semangko fault). These three tectonic systems have caused high seismic activity and have implications for ground movement (Peak Ground Acceleration). This research calculates the PGA value using the Donovan model based on historical data from 50 years of destructive earthquakes. The results of this calculation are mapped and obtained results that have similarities with the tectonic system, where the west coast is a high-risk area for ground movement. The model gives PGA results in the range 8.5508 - 70.4302 gal with a minimum value of 3.295 N, 95.982 E caused by earthquake 9.1 SR, Andaman Island. The maximum value is at 5.57 N, 95.374 E.caused by earthquake 7 SR, Banda Aceh. In general, this map provides an overview of the risk of land movement on the island of Sumatra and can be used for land movement disaster mitigation efforts. Keywords: Donovan, PGA, Sumatran Share Link | Plain Format | Corresponding Author (Tati Zera)

25	Earth and Planetary Sciences	ABS-99
Refining the Regional Aftershocks Catalog of the Ambon Earthquake MW 6,5 on 26th September 2019 using manual picking and a non-linear algorithm: Preliminary Result B Kamaruddin(a*,d), A D Nugraha(b), D P Sahara(b), and Y Halauwet(c,e) a) Master Program of Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology *basri.kamaruddin[at]students.itb.ac.id b) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology c) Earth Sciences Graduate Program, Faculty of Earth Sciences and Technology, Bandung Institute of Technology d) Agency for Meteorology, Climatology, and Geophysics (BMKG), Ternate, Indonesia e) Agency for Meteorology, Climatology, and Geophysics (BMKG), Ambon, Indonesia Abstract A destructive earthquake with magnitude MW 6.5 occurred in Ambon, Indonesia, on 26th September 2019. This earthquake generated an aftershock sequence. In this study, we determined the location of the aftershocks sequence using a non-linear algorithm from the Non-Linear Location (NonLinLoc) program. The catalogue and waveform data were collected using 11 seismographs from BMKG regional network located around Maluku archipelago. The data was recorded between 26th September till 18th October 2019. We have manually picked the P-and-S wave phase by using Seisgram2K software. In our preliminary results, we have located about 1,300 events of aftershock sequence with about 8,500 phases of P and S waves. Overall, the location of the focus depth of the aftershocks sequence is dominantly distributed in between 5 - 25 km. Approximately ~70% of the distribution of aftershock locations show a North-South (N-S) oriented pattern from west Seram to Ambon Islands. Meanwhile, about ~20% of the aftershock^s locations are distributed around Ambon Island. Our ongoing and future study is to determine accurate hypocentre location derived from double-difference hypocenter relocation with waveform cross-correlation. Keywords: Ambon earthquake 2019- Repicking P & S- Non-linear algorithm- Hypocenter location- Waveform cross-correlation Share Link | Plain Format | Corresponding Author (Basri Kamaruddin)

26	Earth and Planetary Sciences	ABS-101
Development of Azimuthal Resistivity Survey Data Processing Program with Graphical User Interface for Anisotropy Coefficient Quantification Berith Atmaodi, Wahyudi W. Parnadi Department of Geophysical Engineering, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, Indonesia Abstract The physical properties of underground material are anisotropic. This applies to all physical properties including resistivity. Anisotropic property is quantified by the anisotropic coefficient. The anisotropy of physical properties can be shown by 2D and or 3D modeling, but it is not always efficient economically for small-scale studies, while 1D modeling is not capable of showing the anisotropy effect. One of the many geophysical methods developed to learn about anisotropic properties under the earth is the azimuthal resistivity survey (ARS) which is the improvement of the vertical electrical sounding (VES) method. Measurement is carried out in one dimension with various electrode spacing and azimuth of electrode lines. The result of this measurement is VES data for various azimuths. ARS data is then plotted with a polar plot to show the anisotropy of physical properties below the surface. The anisotropic coefficient calculation is carried out by performing the one-dimension inversion of the measurement data for every azimuth, for a user-defined number and constant thickness of the layer. The result is then used to calculate the variation of the anisotropic coefficient value against depth. The algorithm used to create the polar plot and VES data inversion are then combined into one program based on Python programming language. This program is equipped with a graphical user interface (GUI) to make the program more user-friendly. The program is tested with synthetic data and successfully imaged the anisotropic coefficient variation against depth from the synthetic data. Keywords: anisotropy- azimuthal resistivity survey- graphical user interface Share Link | Plain Format | Corresponding Author (Berith Atmaodi)

27	Earth and Planetary Sciences	ABS-102
Features Engineering and Features Extraction of Volcano-Tectonic (VT) Earthquake Martanto (a*,c), Andri Dian Nugraha (b), David P. Sahara (b), Zulfakriza (b), Devy Kamil Syahbana (c), Imam C. Priambodo (a, c), Puput P. Rahsetyo (a), Ardianto (a) a) Master Program of Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia. * martanto[at]live.com b) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia. c) Center for Volcanology and Geological Hazards Mitigation, Geological Agency, Ministry of Energy and Mineral Resources, Indonesia. Abstract Volcano-Tectonic earthquake or commonly referred to as VT is an earthquake caused by magma intrusion that increases the pressure below the surface of the volcano. The accumulation of stress that continuously affects the elasticity of rocks causes fractures when the elasticity limit of rocks is exceeded. VT is one of the earthquakes that is used as a parameter to determine the level of volcanic activity. To understand the characteristics of VT, it is necessary to do features engineering which is a process of extraction features so that the characteristics of VT are obtained. The data used in this study were 2,726 VT events and 11,533 waveforms of Agung volcano during the 2017 crisis. The extraction process is conducted by performing statistics calculations in temporal and spectral domains. Waveform of VT is univariate time series data and to perform the extraction features, this study using changes in amplitude value to the time taken from the waveform. Features that were successfully extracted from this study are as many as 102 features for each domain. The result of the extraction of these features can then be used as input parameters in performing auto classification of VT using machine learning. Keywords: volcanology, volcano-tectonic, machine learning, features engineering, features extraction Share Link | Plain Format | Corresponding Author (Martanto Martanto)

28	Earth and Planetary Sciences	ABS-103
Automatic Hiperbola Detection and Apex Extraction Using Convolutional Neural Network on GPR Data Daffa Dewantara(a*), Wahyudi W. Parnadi (a) a) Department of Geophysical Engineering, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung, Indonesia. Abstract Ground Penetrating Radar (GPR) is a non-destructive geophysical method used for subsurface mapping. It is frequently used for detecting buried cylindrical objects such as underground pipes and cables. Buried cylindrical objects show a hyperbolic signal pattern on a radargram. The typical shape of the hyperbolic reflections depends on the depth and material of the buried objects and the surrounding materials. In many cases, detecting buried cylindrical objects is quite a time-consuming task, thus limiting further interpretation procedures. In this paper, we propose a new method in automating hyperbola detection on radargram, by combining object detection methods through convolutional neural network, and digital image processing techniques. Our work consists of three steps. The first step is pre-processing, which is then followed by converting the data to raster format. In the second step, we used the Faster-RCNN to extract the hyperbola segments as a set of rectangular boundary boxes. The convolutional neural network was trained using synthetic data simulated by the gprMax software. The third step is to estimate the coordinates of the hyperbola apex using a search window algorithm on a digital image. Using these three steps, the detection of buried cylindrical objects using GPR can be automated with a minimal amount of time. Keywords: Ground penetrating radar- object detection- radargram- convolutional neural network- gprMax Share Link | Plain Format | Corresponding Author (Daffa Dewantara)

29	Earth and Planetary Sciences	ABS-106
A Preliminary Result of Horizontal to Vertical Spectral Ratio Analysis for Seismic Hazard Calculation in Semarang City, Central Java, Indonesia Meta Nisrina Syafitri(1), Zulfakriza(2,3), Andri Dian Nugraha(2,3), Bambang Prayitno(4), Nanang T Puspito (2,3) 1) Master Program of Geophysical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia. 2) Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung, Indonesia. 3) Center for Earthquake Science and Technology, Institut Teknologi Bandung, Bandung, Indonesia. 4) Meteorological, Climatological and Geophysical Agency of Indonesia, Jakarta, Indonesia. Abstract Semarang city is one of big city in Indonesia which has dense population. Earthquake hazard of Semarang city comes from some active faults lineation which are located around Semarang city, such as Semarang fault, Ungaran fault, and Rawa Pening fault. Rather then, Semarang city is a coastal city which is has thick sediment that susceptible of amplification due to earthquake shaking. We investigate depth of engineering bedrock based on dominant period and S-wave velocity at 750m/s in Semarang city. Dominant period and depth of engineering bedrock are linked with depth of sediment which affect amplification on the ground surface when earthquake occur. We used microtremor data from 91 stations in Semarang city that conducted by Meteorogical, Climatological, and Geophysical Agency of Indonesia (BMKG). The microtremor data is processed using Horizontal to Vertical Spectral Ratio (HVSR) method to obtain dominant period which is reciprocal of dominant frequency. Then we invert the H/V curve to obtain depth of engineering bedrock using Neighbourhood Algorithm. We obtained as preliminary result the dominant period relatively high in northern part of Semarang city and probably correspond to thickness of engineering bedrock. Keywords: HVSR, Dominant period, Engineering bedrock, Semarang Share Link | Plain Format | Corresponding Author (Meta Nisrina Syafitri)

30	Earth and Planetary Sciences	ABS-108
The Effects of Physical and Geometrical Properties on Rock Brittleness Index Based on Numerical Modeling Farhan Hamid Lubis (a*), Fatkhan (a), Umar Fauzi (b) a) Geophysical Engineering, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132, Indonesia *farhanhamidlubis[at]gmail.com b) Physics of Earth and Complex Systems, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132, Indonesia Abstract Rock brittleness is a key parameter to quantify and evaluate the brittle nature of rock. A better estimating technique of rock brittleness is crucial for acquiring an efficient simulation of unconventional shale gas reservoir such as hydraulic fracturing. One way to predict rock brittleness index is by using rock elastic moduli. This physical properties are highly depends on complexity of the micro-structure, fluid content and mineral composition. Micro CT imaging provides a tool for describing an accurate image of pore geometry in a rock. In this study, rock brittleness index estimation was carried out based on elastic properties on numerical models and digital rock images using finite element method. We then evaluate the effect of physical and geometrical properties (pore aspect ratio, mineral composition, and water saturation) in determining the rock brittleness characteristic. The results indicate that there was an increase in Young modulus along with increasing pore aspect ratio to 1 which in turn increasing the rock brittleness. Fluid saturation in this case water saturation cause brittleness to be reduced. The rock mineral composition such as abundant quartz and carbonates content yield high brittleness values, while high clay content and porosity lower the rock brittleness. Overall, the results imply that pore geometry, fluid saturation and mineral composition significantly alters the rock strength parameters. Keywords: Digital Rock Images- Finite Element Method- Effective Ellastic Modulus- Brittleness Index Share Link | Plain Format | Corresponding Author (Farhan Hamid Lubis)

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