Article Per Year (5 Year)
p-Index From 2021 - 2026
0.835
P-Index
This Author published in this journals
All Journal Georest: Geoscience, Remote Sensing, and Technology
Pakhrur Razi
Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Padang, Padang 25131
Astronomy Earth & Planetary Sciences Physics

Published : 5 Documents Claim Missing Document
Claim Missing Document
Check
Articles

Found 5 Documents
Search

 1 
Surface Monitoring of the Grasberg Open Pit Mine Using Sentinel-1A Data Tiara Putri Elizet; Pakhrur Razi; Suci Rizki
GeoREST Vol. 4 No. 1 (2026): Georest
Publisher : EarthCare

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.57265/georest.v4i1.132

Abstract

The Grasberg Open Pit Mine, operated by PT Freeport Indonesia, experiences significant and dynamic ground displacement driven by ongoing, intensive surface and subsurface mining operations. To effectively monitor these complex structural shifts, this study employs Sentinel-1A Synthetic Aperture Radar (SAR) satellite imagery in conjunction with the Interferometric SAR (InSAR) technique to quantify surface deformation with high millimeter-level accuracy across the mining complex. The comprehensive data processing workflow involved multi-temporal C-band Sentinel-1A acquisition, precise interferogram formation, coherence estimation, phase unwrapping, and phase-to-displacement conversion to systematically map line-of-sight (LOS) movements. The empirical results revealed localized land subsidence reaching up to approximately 25 mm, alongside localized surface uplift reaching up to 15 mm over selected observation periods throughout 2025. Furthermore, these spatial deformation patterns highlight the critical influence of localized structural geology, hydrology, and steep topographic gradients on overall slope stability. Ultimately, these findings underscore the high reliability, broad coverage, and cost-effectiveness of spaceborne InSAR for continuous, high-resolution surface deformation monitoring. Integrating routine radar satellite telemetry into site management offers essential early-warning insights for pit slope hazard management, significantly mitigating landslide risks and supporting safer mining practices.
Analysis Of Surface Deformation Due To The Manay Earthquake, Philippines, Using The Interferometric Synthetic Aperture Radar (InSAR) Method Based On Sentinel-1c Data Habibillah Alva Putra Alva; Pakhrur Razi
GeoREST Vol. 4 No. 1 (2026): Georest
Publisher : EarthCare

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.57265/georest.v4i1.140

Abstract

The Philippines is one of the most tectonically active regions in the world, situated at the convergence of several major and minor plates, including the Philippine Sea Plate, the Sunda Plate, and the Eurasian Plate. This complex tectonic setting makes the archipelago highly susceptible to frequent and often destructive earthquakes, which can trigger significant deformation of the ground surface, infrastructure damage, and secondary hazards such as landslides and liquefaction. One notable seismic event occurred in the Manay region, Mindanao, Philippines, generating measurable surface displacement that requires accurate spatial assessment for effective disaster response and mitigation planning. However, ground-based monitoring alone is often insufficient to capture the spatial extent and pattern of coseismic deformation, particularly in remote or rapidly affected areas. This study addresses this gap by employing the Interferometric Synthetic Aperture Radar (InSAR) technique to analyze surface deformation associated with the Manay earthquake, utilizing Sentinel-1C Single Look Complex (SLC) imagery. Pre-event and post-event SAR acquisitions were processed to generate interferograms, phase decomposition, and line-of-sight surface displacement maps. The InSAR approach enables wide-area deformation monitoring with high spatial resolution and centimeter-level accuracy, offering advantages over conventional in-situ measurement techniques. The resulting deformation maps reveal the spatial distribution and magnitude of ground displacement induced by the earthquake. These findings are expected to enhance the understanding of coseismic surface behavior in tectonically active regions and to serve as a valuable reference for future disaster risk assessment, seismic hazard mapping, and mitigation strategies in the Philippines and similar geodynamic settings.
Tropical Cyclone Intensity Modeling Using the Dvorak  Technique Based on Satellite Observations Yuli Fitria; Pakhrur Razi
GeoREST Vol. 4 No. 1 (2026): Georest
Publisher : EarthCare

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.57265/georest.v4i1.141

Abstract

Tropical cyclones are among the most destructive atmospheric phenomena in tropical and subtropical regions, producing extreme winds, heavy rainfall, storm surges, and severe socio-economic impacts. Accurate estimation of tropical cyclone intensity is therefore essential for disaster risk reduction, particularly over oceanic regions where in-situ observations are limited. This study examines the temporal evolution of tropical cyclone intensity using the Dvorak Technique applied to satellite infrared and visible imagery during the period 27–29 November 2017. Distinct cloud structural patterns, including Curved Band, Central Dense Overcast, Embedded Center, and Eye Pattern, were systematically identified to derive T-numbers and Current Intensity (CI) values. These intensity estimates were converted into maximum sustained wind speeds using standard Dvorak–NOAA conversion tables. The results indicate a clear intensification sequence from a weak tropical system (T2.0) to a mature cyclone reaching a peak intensity of T5.5, corresponding to a maximum sustained wind speed of approximately 102 knots (≈188 km h⁻¹). A pronounced rapid intensification phase was detected, characterized by an increase exceeding 30 knots within a 24-hour period. The strong correspondence between cloud structural evolution and intensity variability confirms the robustness of the Dvorak Technique for tropical cyclone modeling and hazard assessment in data-sparse tropical regions.
Drought Disaster Analysis Using the Standardized Precipitation Index (SPI) Under the Influence of ENSO and the IOD in the Northern Region of Banten Province (1991–2020 Period) Dodi Saputra; Pakhrur Razi
GeoREST Vol. 4 No. 1 (2026): Georest
Publisher : EarthCare

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.57265/georest.v4i1.144

Abstract

Drought is a physical phenomenon that begins with reduced rainfall (meteorological drought) and can develop into agricultural and hydrological drought through heat and water-vapor transfer processes driven by sea surface temperature anomalies such as El Niño and the Positive Dipole Mode (IOD), which suppress cloud formation and rainfall over Indonesia. This study in the northern region of Banten Province (Serang and Tangerang) for the 1991–2020 period analyzes meteorological drought using the Standardized Precipitation Index (SPI) and relates it to ENSO (ONI) and the IOD. The results show that the most severe extreme drought occurred during the three-month deficit period of October–December 1997 with an SPI of −3.9 and during the six-month deficit period of January–June 2003 with an SPI of −4.1, while the most spatially widespread drought pattern across northern Banten occurred during the three-month SPI period. A strong El Niño event (ONI > +2) and a positive IOD phase (IOD > +1) in 1997 were associated with reduced atmospheric moisture and decreased rainfall, triggering extreme drought that appeared widespread in the three-month SPI map.
Analysis of Vegetation Changes After the 2023 eruption of Mount Marapi in Google Earth Engine Hamdy Arifin; Pakhrur Razi; Yuta Izumi
GeoREST Vol. 4 No. 1 (2026): Georest
Publisher : EarthCare

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.57265/georest.v4i1.146

Abstract

The eruption of Mount Marapi in late 2023 caused substantial environmental disturbance, particularly to vegetation cover on its slopes and surrounding areas. Ashfall and pyroclastic deposits reduced vegetation health by covering leaf surfaces and disrupting photosynthetic activity, yet the spatial extent and severity of this impact have not been systematically quantified. This study analyzes vegetation changes before and after the eruption using the Normalized Difference Vegetation Index (NDVI) and Normalized Burn Ratio (NBR) derived from Sentinel-2 imagery processed on the Google Earth Engine (GEE) platform. The analysis covers a 35 km radius from the crater, comparing a pre-eruption period (1 November–22 December 2023) with a post-eruption period (24 December 2023–20 February 2024). Results reveal a marked decline in mean NDVI from 0.58 to 0.33 and mean NBR from 0.56 to 0.29, corresponding to approximately 43% vegetation degradation attributable to volcanic activity. Spatial analysis of ΔNDVI and ΔNBR further indicates that 45–50% of the slope area experienced moderate to severe damage, concentrated on the east and southeast flanks, consistent with the dominant direction of ash dispersal, whereas the foothill zones showed early signs of vegetation recovery within two months. These findings confirm that cloud-based multi-temporal Sentinel-2 processing on GEE offers a rapid and reliable approach for post-eruption vegetation monitoring, providing a quantitative basis for land rehabilitation planning and environmental risk management in volcanic disaster-prone regions.
Co-Authors Dodi Saputra Habibillah Alva Putra Alva Hamdy Arifin Suci Rizki Tiara Putri Elizet Yuli Fitria Yuta Izumi