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Sandri Erfani, S.Si, M.Eng.
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Geophysical Engineering Department Engineering Faculty Universitas Lampung, Prof. Dr. Sumantri Brojonegoro Street No 1, Rajabasa District, Bandar Lampung, Indonesia 35145
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JGE (Jurnal Geofisika Eksplorasi)
Published by Universitas Lampung
ISSN : 23561599     EISSN : 26856182     DOI : https://doi.org/10.23960/jge
Core Subject : Science,
Earth & Planetary Sciences
Jurnal Geofisika Eksplorasi adalah jurnal yang diterbitkan oleh Jurusan Teknik Geofisika Fakultas Teknik Universitas Lampung. Jurnal ini diperuntukkan sebagai sarana untuk publikasi hasil penelitian, artikel review dari peneliti-peneliti di bidang Geofisika secara luas mulai dari topik-topik teoritik dan fundamental sampai dengan topik-topik terapandi berbagai bidang. Jurnal ini terbit tiga kali dalam setahun (Maret, Juli dan November), Volume pertama terbit pada tahun 2013 dengan nama Jurnal Geofisika Eksplorasi (JGE).
Arjuna Subject : Ilmu Bumi dan Planet (semua kategori) - Ilmu Bumi dan Planet (Lain-Lain)
Articles 216 Documents
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LAST GLACIAL MAXIMUM – HOLOCENE RAINFALL SHIFTS IN THE WESTERN SAVU STRAIT BASED ON GEOCHEMICAL PROXIES Ardi, Ryan Dwi Wahyu; Aswan, Aswan; Maryunani, Khoiril Anwar; Yulianto, Eko; Putra, Purna Sulastya; Nugroho, Septriono Hari; Nurhidayah, Efrilia Mahdilah
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 2 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i2.493

Abstract

The Indo-Pacific Warm Pool significantly influences global atmospheric circulation, with tropical rainfall patterns highly sensitive to glacial–interglacial climate changes. During the Last Glacial Maximum (LGM), approximately 26,500 years before present, lower insolation, expanded ice sheets, and reduced sea levels weakened the Australian–Indonesian Monsoon (AIM) due to a southward shift of the Intertropical Convergence Zone (ITCZ). In contrast, the Holocene period experienced intensified monsoon systems and increased precipitation. However, high-resolution hydroclimate reconstructions from the western Savu Strait remain scarce. This study reconstructs rainfall variability from the LGM to the Holocene using geochemical proxies from sediment core ST10 (at 1 cm interval), located in the western Savu Strait. Three elemental ratios (Ti/Ca, K/Ca, and Rb/Sr) from X-ray fluorescence (XRF) core scanning were used to indicate terrigenous input, chemical weathering, and fluvial discharge. The age model was established using radiocarbon dating and stable isotope alignment with the Greenland ice core δ¹⁸O record. Log-transformed elemental ratios reveal four intervals of increased rainfall: the LGM, Heinrich Event 1 (HE1), Younger Dryas to Early Holocene, and the Late Holocene. These periods are characterized by elevated Ti/Ca, K/Ca, and Rb/Sr values, suggesting enhanced monsoonal rainfall and continental runoff. Conversely, lower proxy values during the Early Deglaciation, Bølling–Allerød, and Mid-Holocene indicate drier climatic conditions. These patterns align with regional proxy records from southwest Sumba and the Timor Sea, confirming the reliability of elemental ratios in reconstructing past hydroclimate variability. This study provides the first continuous record of rainfall shifts in the western Savu Strait from the LGM to Holocene and contributes to understanding long-term monsoon dynamics in southeastern Indonesia, highlighting the complex response of tropical hydroclimate to global climate forcing.
SITE EFFECTS IDENTIFICATION USING HVSR METHOD IN CISARUA HOT SPRING AREA, NATAR, SOUTH LAMPUNG Farduwin, Alhada; Nugraha, Purwaditya Nugraha; Styawan, Yudha; Lestari, Eka Yunita Purnama; TR, Dina Puspita Julyanti
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 2 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i2.494

Abstract

Cisarua, which contains a geothermal hot spring, is an intriguing area to investigate due to its location far from any known heat source or volcanic activity. Using the HVSR technique, this study aims to characterize the local site effects based on key parameters: natural frequency (fo), amplification factor (Ao), and average shear-wave velocity down to 30 meters depth (Vs30). Microtremor measurements were conducted at 25 locations across the Cisarua hot spring area, with an average spacing of 300 meters. Each site was recorded for 40–50 minutes, and the data were processed using Geopsy software to extract the HVSR curves, along with the fo and Ao values. The HVSR curves were then inverted using the Particle Swarm Optimization (PSO) algorithm to derive Vs30 values. The results show that fo values range from 0.6 to 1.1 Hz, and Vs30 values are generally below 175 m/s. These two parameters exhibit minimal spatial variation, indicating the presence of thick, soft, and relatively homogeneous sedimentary layers across most of the study area. The Ao values range from 2 to 5, with values below 3 dominating near the geothermal manifestation zone. The spatial distribution of fo and Ao reveals a northwest–southeast trend, which is strongly correlated with the presence of the Lampung–Panjang Fault that likely controls sediment accumulation and layer thickness in the area. Around point T13, Vs30 drops to 125–150 m/s, suggesting localized softening of the soil due to hydrothermal alteration processes. These findings emphasize the interplay between site effects, regional geological structures, and geothermal activity in shaping the dynamic properties of the subsurface in this area.
TEMPORAL AND DEPTH VARIATION OF SEISMIC PARAMETERS PRIOR TO MAJOR EARTHQUAKES IN PALU REGION, INDONESIA Rahmalia, Diah Ayu; Andinisari, Ratri; Tampubolon, Danastri Lintang Pitaloka; Aminuddin, Jamrud; Yuliardi, Amir Yarkhasy; Fadhilah, Firda Haifa
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 3 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i3.498

Abstract

The Palu region in Central Sulawesi is high tectonic activity area due to a subduction zone and major fault system, which resulted in high seismic intensity. The b value, as the seismic characteristic, is a valuable parameter for evaluating stress conditions and earthquake precursors. This study aimed to investigate the temporal and depth variations of the b-value in the Palu region. We observed earthquake distribution over 75 years from 1950 to 2025, which was obtained from the United States Geological Survey catalog. We applied the declustering analysis to isolate the mainshock events by using the space-time window method. We also conducted the magnitude completeness estimation and b-value calculation with ZMAP. This result showed that the average b-value was around 0.88, which was indicated as an intermediate level of seismic activity, influenced by subduction and the Palu-Koro Fault. Decreasing b-value was observed prior to the 1996 and 2018 earthquakes, followed by an increase in the parameter. This pattern exhibited stress accumulation and release, which was represented by the magnitude distribution. This lowering characteristic of b-value could be a long term precursor to major earthquakes. Furthermore, the depth variation of b-value revealed high values in the upper crust (0–10 km), a decrease around 20–30 km, and a secondary increase near 40 km, which corresponds to the Moho, as indicated by shear wave velocity profiles. These results provide insight into the crustal structure and seismic behavior in a tectonically complex and tsunami-prone region.
Cover JGE JGE, Editor
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 2 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i2.499

Abstract

Cover JGE
Foreword July 2025 JGE, Editor
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 2 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i2.500

Abstract

Foreword July 2025
PEMETAAN MAGNITUDE OF COMPLETENESS (Mc) UNTUK GEMPA DI WILAYAH BENGKULU Hanafi, Ridwan; Dewi, Ira Kusuma; Ngatijo, Ngatijo
JGE (Jurnal Geofisika Eksplorasi) Vol. 10 No. 2 (2024)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v10i2.250

Abstract

Dengan menggunakan data gempa bumi dari katalog USGS dan BMKG dari tahun 2009 hingga 2021, penelitian dilakukan untuk mengestimasi nilai Mc, nilai-b, dan nilai-a. Gempa bumi terjadi pada 6° LS - 2° LU dan 100° BT - 103° BT, dengan magnitudo 3 SR hingga 7 SR, dan kedalaman tertinggi adalah 300 km, yang mencakup wilayah provinsi Bengkulu. Penelitian ini dilakukan dengan menggunakan metode EMR dan software ZMAP 6.0 di Matlab digunakan. Menurut analisis di atas, USGS memperoleh Mc sekitar 4,7 SR hingga 5, nilai-b berkisar 0,9 hingga 1,5, dan variasi nilai-a sekitar 6 hingga 9,5. Sebaliknya, BMKG memperoleh Mc sekitar 3,8 hingga 5,2, nilai-b berkisar 0,55 hingga 0,85, dan variasi nilai-a sekitar 5,2 hingga 5,8.  Pemetaan nilai Mc menunjukkan bahwa semua kabupaten di Provinsi Bengkulu memiliki nilai Mc yang rendah, yang menunjukkan bahwa data gempa untuk daerah-daerah ini cukup lengkap dibandingkan dengan daerah lain. Menurut pemetaan nilai-b dan nilai-a, wilayah yang memiliki tingkat kegempaan yang relatif tinggi dan memiliki potensi gempa besar berada di sekitar wilayah timur laut dan tenggara Provinsi Bengkulu.
GEOMORPHIC INDICES AND FAULT SEGMENTATION INDICATION OF MENANGA FAULT AT PESAWARAN, LAMPUNG Hendrawan, Rezki Naufan; Draniswari, Windi Anarta; Bakhtiar, Agim Yustian; Widiatama, Angga Jati
JGE (Jurnal Geofisika Eksplorasi) Vol. 9 No. 3 (2023)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v9i3.287

Abstract

Remote sensing and GIS are playing important roles in geomorphology and hazard risks analysis. Pesawaran area located near the Menanga Fault and recently on the risk of earthquake that happened along this fault.  Thus, it is essential to investigate the area actively affected by Menanga Fault as preliminary research about hazard risk related to Menanga Fault. The morphometry method based on DEMNAS and Landsat 8 was applied to evaluate the zone affected by Menanga Fault, and fracture data analysis was conducted to consider the possibility of fault segmentation resulting from its mechanism. The study area can be divided into 3 zones; zone A is greatly affected by Menanga Fault activity, zone B is affected by Menanga Fault and Mt. Pesawaran development, and zone C is tectonically less affected. Zone A landforms were not only formed as a result of Menanga Thrust fault but also the strike-slip fault segment.  Fault segmentation exists in this zone with different mechanisms (strike-slip and dip-slip), producing lineaments with different trends, and differentiation of river patterns.
MIKROZONASI TINGKAT KERENTANAN LAPISAN TANAH KECAMATAN NAMBO, KENDARI MENGGUNAKAN METODE HORIZONTAL-TO-VERTICAL SPECTRAL RATIO Rubaiyn, Al; Hamimu, La; Mukarramah, Mukarramah
JGE (Jurnal Geofisika Eksplorasi) Vol. 9 No. 3 (2023)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v9i3.292

Abstract

Penelitian respons dinamik dan indeks kerentanan seismik sangat penting untuk memperkirakan dampak kerentanan lapisan permukaan dan kerusakan bangunan ketika terjadi gempa bumi.  Penelitian ini bertujuan untuk mengidentifikasi respons dinamik Kecamatan Nambo, Kota Kendari serta menentukan area-area dengan perlapisan tanah yang sangat rentan. Data mikrotremor diolah menggunakan Geopsy 2.0.5 untuk memperoleh kurva HVSR (Horizontal to Vertical Spectral Ratio) serta parameter respons dinamik tanah berupa frekuensi dominan dan faktor amplifikasinya yang digunakan untuk menghitung indeks kerentanan seismik. Nilai frekuensi dominan Kecamatan Nambo berkisar antara 0,7 Hz- 3,63 Hz yang termasuk dalam kategori tanah Tipe II dan III. Area dengan frekuensi rendah menunjukkan penebalan lapisan alluvial yang merupakan produk sedimentasi permukaan. Interpolasi nilai indeks kerentanan seismik (kg) menunjukkan area Kecamatan Nambo yang memiliki kerentanan tinggi meliputi Kelurahan Pentoahan dan Nambo.
ANALISIS TENSOR FASE DAN PEMODELAN 2D DATA MAGNETOTELURIK GABBS VALLEY, NEVADA, USA Pahri, Pahri; Paembonan, Andri Yadi; Irawati, Selvi Misnia
JGE (Jurnal Geofisika Eksplorasi) Vol. 9 No. 3 (2023)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v9i3.301

Abstract

Metode magnetotellurik (MT) merupakan salah satu teknik dalam metode geofisika yang menggunakan sumber alami dalam bentuk medan elektromagnetik yang berasal dari medan listrik dan variasi medan magnet di bumi. Dalam proses interpretasi kondisi bawah permukaan bumi, data MT masih dipengaruhi oleh noise atau distorsi yang akan menutupi dimensionalitas sebenarnya. Oleh karena itu dilakukan analisis tensor fase untuk menentukan dimensionalitas dan arah geoelectrical strike guna mengidentifikasi struktur bawah permukaan yang tidak dipengaruhi oleh distorsi galvanic. Berdasarkan hasil yang diperoleh, daerah penelitian memiliki dimensionalitas 2D dengan orientasi barat laut – tenggara dengan arah N345 E. Hasil inversi 2D menunjukkan bahwa nilai resistivitas < 10  diidentifikasi sebagai zona alterasi atau clay cap yang didominasi oleh mineral smektit. Nilai resistivitas 20 – 250  diidentifikasi sebagai reservoar yang bersifat permeabel yang tersusun atas batu pasir kasar, kerikil, basal, andesit, riolit, riodasit tuff dan konglomerat. Lapisan dengan nilai resistivitas > 250  diidentifikasi sebagai Upper Triassic Metasediment yang mengalami sedimentasi yang sangat keras, hal tersebut disebabkan tekanan dan suhu tinggi. Lapisan ini tersusun atas meta batu lanau, batu lempung, meta batu pasir, dan meta konglomerat.
MODEL OF LATERITE NICKEL DEPOSITS BASED ON LGSO AND HGSO VALUES PT MITRA KARYA AGUNG LESTARI Asmiani, Nur; Thamsi, Alam Budiman; Nompo, Supardin; Bakri, Suryanto; Tukloy, Muh. Yusril Affandy; Harmitun, Harmitun
JGE (Jurnal Geofisika Eksplorasi) Vol. 10 No. 1 (2024)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v10i1.305

Abstract

The laterite nickel deposit model provides information about the form of laterite nickel deposits below the surface, which can be used as one of the considerations in the implementation of mining activities. The purpose of conducting this research is to determine the distribution model of nickel laterite deposits in 3 dimensions (3D) and to determine the amount of nickel laterite reserves based on high-grade saprolite ore (HGSO) and low-grade saprolite ore (LGSO) values in the DH Block. In this research, Inverse Distance Weighted (IDW) is used to estimate nickel laterite resources, which are applied using mining software Surpac 6.3.2 to produce a model in 3D form. The data used are laterite nickel content data (assay), x, y, and z coordinate data (collar), survey data, and lithology data. Based on IDW estimation results with a Cut Off Grade (COG) value of 1.3 in the DH Block of PT Mitra Karya Agung Lestari, High-Grade Saprolite Ore (HGSO) values were obtained at Ni content > 1.7 and Low-Grade Saprolite Ore (LGSO) at Ni content > 1.3, with a tonnage value of 111.994 tons of HGSO and 371.044 tons of LGSO.

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