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All Journal Quimica : Jurnal Kimia Sains dan Terapan Geoid - Journal of Geodesy and Geomatics
Rizky, Sari
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Agriculture, Biological Sciences & Forestry Chemistry Earth & Planetary Sciences Engineering Environmental Science

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Analisis Perubahan Struktur Mineral Tanah Akibat Reaksi Kimia antara Lempung dan Kapur pada Kondisi Kelembapan Tinggi Sabilla, Arissa; Rikza, Rikza; Alfisyahrin, Alfisyahrin; Masthura, Masthura; Rizky, Sari; Damayanti, Rizki
JURNAL QUIMICA Vol 7 No 2 (2025)
Publisher : Program Studi Kimia, Fakultas Sains dan Teknologi, Universitas Samudra

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33059/jq.v7i2.13354

Abstract

Penelitian ini bertujuan untuk menganalisis perubahan struktur mineral tanah akibat reaksi kimia antara lempung dan kapur pada kondisi kelembapan tinggi dengan memanfaatkan data sekunder hasil uji laboratorium terdahulu. Analisis difokuskan pada hubungan antara variasi kadar kapur terhadap perubahan sifat mekanik dan mekanisme kimia yang mendasarinya. Bahan penelitian berupa tanah lempung berplastisitas tinggi (CH) yang distabilisasi menggunakan kapur padam (Ca(OH)₂) pada kadar 0%, 2%, 4%, 6%, 8%, 10%, dan 12% dari berat kering tanah. Hasil pengujian menunjukkan bahwa penambahan kapur hingga kadar optimum 6% meningkatkan nilai sudut geser dalam (ϕ) dari 20,545° menjadi 39,330°, serta kohesi (c) dari 1,505 t/m² menjadi 2,080 t/m². Peningkatan kekuatan ini disebabkan oleh terbentuknya senyawa Calcium Silicate Hydrate (CSH) dan Calcium Aluminate Hydrate (CAH) hasil reaksi pozzolanisasi antara ion Ca²⁺ dari kapur dan mineral silikat–aluminat dari tanah lempung. Kelembapan tinggi mempercepat proses difusi ion dan pembentukan senyawa pengikat tersebut, sehingga struktur tanah menjadi lebih rapat dan kaku. Namun, pada kadar kapur di atas 10%, reaksi kimia tidak berjalan efektif karena terbentuk lapisan jenuh Ca(OH)₂ yang menghambat difusi ion. Secara geoteknis, kondisi optimum tercapai pada kombinasi kadar kapur 6–8% dengan kelembapan tinggi yang terkontrol, yang mampu meningkatkan kekuatan geser dan menurunkan plastisitas tanah secara signifikan.
Estimation of 2021 M7.3 Flores Sea Earthquake Displacement Derived from Static GNSS Observation Maulida, Putra; Herawati, Yola Asis; Rizkiya, Putra; Rizky, Sari; Kurniawan, Akbar; Azza Laksono, Safanata; Budisusanto, Yanto
GEOID Vol. 20 No. 2 (2025)
Publisher : Departemen Teknik Geomatika ITS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/geoid.v20i2.8500

Abstract

On 12 December 2021, a Mw 7.3 strike-slip earthquake ruptured a previously unmapped fault in the Flores Sea, later identified as the Kalaotoa fault. The event damaged 345 buildings and displaced nearly 3,900 residents, highlighting the seismic hazard in the Sunda–Banda arc transition zone. In this study, we analyzed static GNSS data from the Indonesian Continuously Operating Reference System (InaCORS) to estimate coseismic displacements. Daily coordinate solutions, corrected for satellite orbit, ionospheric, and tropospheric errors, were processed to extract the coseismic offsets during the event. Results show horizontal displacements of up to 3.0 cm at CFLT, 2.2 cm at CMRE, and 1.9 cm at CUKA, with vertical motions reaching ~1.3 cm uplift at CUKA and ~0.9 cm subsidence at CMRE, which suggests that the earthquake not only incorporates the strike-slip movement but also the dipping movement. Stations near the epicenter moved northwestward, while northern stations moved southeastward, consistent with a right-lateral strike-slip mechanism. To validate the observations, we employed a half-space elastic dislocation model based on centroid moment tensor solutions for fault geometry. The model reproduced the general displacement patterns but showed systematic discrepancies, including overestimation of horizontal offsets by nearly a factor of two at near-epicenter stations (CFLT, CMRE, CUKA, CLWB) and underestimation of vertical motions by up to 2–3 cm. The misfit corresponds to an RMSE of ~1 cm for horizontal and ~3 cm for vertical displacement. These results indicate that a single homogeneous slip model oversimplifies the rupture, suggesting the need for more complex fault segmentation or slip inversion. Overall, this study demonstrates the capability of GNSS to capture coseismic deformation robustly and emphasizes its importance for refining earthquake source models and improving seismic hazard assessment in tectonically complex regions such as eastern Indonesia.
Co-Authors Akbar Kurniawan Alfisyahrin, Alfisyahrin Azza Laksono, Safanata Herawati, Yola Asis Masthura, Masthura Maulida, Putra Rikza, Rikza Rizki Damayanti, Rizki Rizkiya, Putra Sabilla, Arissa Yanto Budisusanto, Yanto