Author: tektonesiana

Hybrid turbidite–contourite systems are present where gravity-driven and bottom-current processes interact. Although recent studies have advanced our understanding, deciphering the relative roles of downslope and alongslope processes in shaping the deep seafloor remains an important subject of investigation. The Tarakan Basin, offshore northeastern Borneo, is a prolific hydrocarbon province, yet its modern sedimentary systems are poorly understood. Shaped by rapid deltaic sedimentation, active tectonics, and ocean currents–the South China Sea Throughflow (SCSTF) and Indonesian Throughflow (ITF) – the basin offers an ideal setting to study hybrid deepwater processes. Here, we conducted seismic sedimentology analysis to quantify morphometric parameters, delineate seismic facies, and interpret depositional processes using 3D seismic reflection data. Three segments are identified. The Northern Segment is dominated by upslope-migrating sediment waves and plastered drifts, indicative of contourite-dominated conditions. The Central Segment hosts a canyon–drift complex, formed by synchronous interaction of turbidity flows and bottom currents. In contrast, the Southern Segment is shaped mainly by turbidity currents, with gullies and associated sediment waves suggesting limited bottom current influence. These spatial variations reflect a spectrum of hybrid depositional styles, consistent with global models of contourite-, synchronous-, and turbidite-dominated systems. The sedimentary patterns observed provide an analogue for subsurface reservoir and seal distribution, relevant to both petroleum and carbon storage systems.

Citation: Nugraha HD and Maulin HB (2025) Hybrid turbidite–contourite systems in the modern Tarakan Basin: seismic sedimentology and analogue for subsurface storage. Front. Earth Sci. 13:1614416. doi: 10.3389/feart.2025.1614416

Journal of Volcanology and Geothermal Research https://doi.org/10.1016/j.jvolgeores.2025.108472

The western Java region is situated along the Sunda Arc, which is formed by subduction of the Indo-Australian Plate beneath the Eurasian Plate. The subduction process causes seismic activity in the Wadati-Benioff zone of the descending slab, produces a chain of active volcanoes, and forms numerous faults in the terrestrial and back-arc region of the overriding plate. This study examines the region’s tectonic system via seismic tomography, in which the most recent earthquake catalog from the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG) is utilized. Body wave travel time from 4561 local-regional earthquakes recorded by 78 seismic stations produces a 3-D Vp and Vp/Vs ratio model. The subducting Indo-Australian Plate slab is characterized mainly by high Vp and low Vp/Vs anomalies and exhibits steeper subduction than the Slab2 model. Partial melting zones, which serve as magma sources for several volcanoes, are observed at depths of about 90–100 km, characterized by low Vp and high Vp/Vs anomalies. The Lembang and Cimandiri fault lineaments are visible at 10 km depth and are characterized by negative Vp and positive Vp/Vs anomalies. This study also successfully demonstrates that the source of the damaging 2022 Cianjur earthquake occurred in a region dominated by low Vp and high Vp/Vs. These anomalies most likely relate to fluids or molten material in the fault zone. This study again highlights the importance of the BMKG seismic network for understanding tectonic systems on a local-regional scale, in this case, through the lens of seismic tomography.

Authors: W. Wandono, M. Ramdhan, A.N. Aulia, A.B.Pangestu, E. Hidayat, S. Syuhada, S. Widiyantoro, Nicholas Rawlinson, T.Anggono, B. Pranata, M.M. Mukti, M.P. Maulana

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Ashar Muda Lubis, Rida Samdara, Rio Sahputra, Lina Handayani, Qiu Qiang, Agnis Triahadini, Muhammad Maruf Mukti, Oktadi Prayoga

Tectonophysics, Volume 914, 25 November 2025, 230879, https://doi.org/10.1016/j.tecto.2025.230879

Highlights

• We modelled GPS data during 2018–2024 to estimate the slip rate and locking depth of Ketahun segment.
• We find the importance of viscoelastic response and megathrust coupling effect in our analysis.
• The Ketahun segment slip rate is 14.5 [−1.2, +1.3] mm/yr and locking depth of 14.4 [−4.9, +4.8] km.
• The Ketahun segment is capable of generating a magnitude ∼6 to 7+ in the future.

Abstract

The Ketahun segment of the Sumatran Fault System (SFS) is distinctive and tectonically active segment, yet the slip rate of the segment is not widely known. The Ketahun segment underwent two major earthquakes of M_s 7.6 in 1946 and M_s 6.8 in 1952, respectively. Using Global Positioning System (GPS) data, we aim to better estimate the slip rates using a dislocation elastic model following a Bayesian approach with Metropolis Markov chain Monte Carlo (MCMC) samplers to estimate optimum fault parameters. Then we determined the potential amount of cumulative energy stored at the segment. We processed raw GPS data from 35 GPS stations, combining from GIA, SuGAr, and UNIB networks during 2018–2024 using GAMIT/GLOBK software. The daily GPS solutions were constrained into the ITRF-2014 frame, and the GPS velocities were translated into Sunda block. Before we model the trench parallel GPS velocities, we attempted to correct the viscoelastic velocities due to the 2007 Mw 8.4 Bengkulu earthquake incorporating the effect of megathrust coupling on the trench parallel GPS velocities. We find the importance of viscoelastic response and megathrust coupling effect in our analysis, providing better slip rate and locking depth estimation. Our result inferred that the estimated fault slip rate is 14.5 [−1.2, +1.3] mm/yr with a locking depth of 14.4 [−4.9, +4.8] km across in the Ketahun segment. The segment is capable of generating a magnitude ∼6 to 7+ if a single earthquake occurs every 50 to 200 years.

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Ini adalah update publikasi kami sampai pertengahan tahun ini. Semoga bermanfaat. Salam.

Godang, S., Saputro, S. P., Li, H., Satyana, A. H., & Srichan, W., 2025. Geochemistry of the Adang volcanics in Western Sulawesi: Unveiling the tectonic evolution of the opening of the makassar strait. Solid Earth Sciences, 10(1), 100228. https://doi.org/10.1016/j.sesci.2025.100228 (open access) [link] [pdf]

Handayani, L., Mukti, M. M., Arisbaya, I., Gaol, K. L., Sudrajat, Y., Lubis, A. M., & Anggono, T., 2025. Basement structure across Renun segment near Toba caldera inferred from the gravity anomaly: Implication for potential earthquake rupture barrier. Geodesy and Geodynamics. https://doi.org/10.1016/j.geog.2025.04.006 (open access) [link] [pdf]

Ramdhan, M., Palgunadi, K. H., Mukti, M. M., Librian, V., Daniarsyad, G., Muttaqy, F., … & Febriani, F., 2025. Aftershock sequence of the Yogyakarta earthquake 2006 (Mw~ 6.4), Indonesia, based on analysis of hypocenter relocation, static, and dynamic stress. Natural Hazards, 1-21, https://doi.org/10.1007/s11069-025-07440-8 [link] [pdf]

Ramdhan, M., Priyobudi, P., Mukti, M. M., Putra, A. S., Hidayat, E., Muttaqy, F., Syuhada S.,
Hanif, M., Widiyantoro, S., Librian, V., Susilawati, A., Madrinovella, I., & Wandono, W., 2025. Tracing fault systems from subsurface to surface in Yogyakarta and its surroundings, Indonesia. Natural Hazards Research, https://doi.org/10.1016/j.nhres.2025.07.003 (open access) [link] [pdf]

Satyana, A.H., (2025). Natural hydrogen systems in various geotectonic settings of Indonesia: Bottom–up approach. Indonesian Petroleum Association Forty-Ninth Annual Convention & Exhibition [link] [pdf]

Satyana, A.H., 2025. Paleogene to Neogene Volcanisms of Eastern Margin of
Sundaland: Petrotectonic Evolution and its Implications to Petroleum Exploration in the Makassar Strait, South Arm of Sulawesi, and Bone Basin. Indonesian Petroleum Association Forty-Ninth Annual Convention & Exhibition [link] [pdf]

Syuhada, S., Muttaqy, F., Anggono, T., Pranata, B., Puspito, N.T., Ramdhan, M., Febriani, F., Mukti, M.M., Dewi, C.N., Hasib, M. and Prasetio, A.D., 2025. Spatial variation of crustal anisotropy in Simeulue Island, Indonesia, from shear wave splitting analysis. Physics of the Earth and Planetary Interiors, p.107362. https://doi.org/10.1016/j.pepi.2025.107362 [link] [pdf]

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Dear RGP readers,

We are delighted to deliver the first issue of Volume 35 of Riset Geologi dan Pertambangan (Geology and Mining Research). This issue publishes five papers dealing with seismic hazards, tectonic geomorphology, and granite mineralogy. Hermawan et al. present their work on distribution of PGA values on bedrock in central Java area using Probabilistic Seismic Hazard Analysis. They further suggest that there is a necessity in earthquake mitigation to minimize losses when a major earthquake occurs in the future. The second article by Fahrezi et al. describes seismic hazard
evaluation using seismic response analysis in Bengkulu area. In the third article, Maryudhaningrum et al. elucidate the role of groundwater extraction and natural consolidation to land subsidence in Bandung Basin.

The fourth article by Faturrakhman et al. presents a new insight into hydrogen exploration by using tectonic geomorphology to identify key target areas based on their tectonic activity in relation to the occurrence of active faults in central Sulawesi area. Whereas, the last paper by Elly et al. is dealing with new petrography and X-ray diffraction data of granite from Hukurila area that contributes in understanding granite petrogenesis in Ambon, eastern Indonesia.

We acknowledge the authors and reviewers for their valuable works and contributions to this issue. Many thanks to the editorial members and staffs for their continuous support for the publication of this first issue of this year. We welcome your scientific contributions for the next upcoming issues.

Sincerely,
The Editors of RGP

We are excited to share that our journal, Riset Geologi dan Pertambangan is now indexed in Scopus and ranked by the SCImago Journal & Country Rank (SJR). 

Riset Geologi dan Pertambangan (Geology and Mining Research) is a gold open-access journal managed voluntarily by Earth science enthusiasts, supported, and published by BRIN Publishing (ISSN 0125-9849, e-ISSN 2354 6638). We believe that Earth science research should be inclusively accessible for everyone. There is no fee to submit manuscripts and no cost to read our peer-reviewed articles.

Our journal publishes research papers, reviews, and short communications in geosciences-related interdisciplinary topics. We are pleased to invite researchers and practitioners in these fields to contribute to the journal by sharing their research, insights, and perspectives. 

Based on analyses of published geological cross sections along the Baribis Fault, we briefly review several possible mechanisms of this backarc thrust that developed behind the volcanic arc in western Java. There is no general agreement regarding the mechanisms of the backarc thrust. Therefore, the origin of this fault remains uncertain. Previous works proposed that the backarc thrust in western Java may have developed as deformation of paleo-accretionary wedge sediments behind a continental backstop, inverted normal fault, northward migrating thrust belt, and thrusting due to gravitational sliding of the volcanic arc. However, evidences supporting those mechanisms still need to be elucidated. Detailed examination of the available geological data might suggest that backarc thrusting in western Java may have formed due to stress transfer through rigid arc blocks. The far-field stress from the subduction zone is propagated through remnants and modern volcanic arcs and finally, deformed sediments in the Bogor Trough that nucleated as backarc thrust.

Authors:

Hanief Ajib Abdalla, Nasywa Dhia Khalifa, Cyntia Adrian Lestari, M. Maruf Mukti, Akhmad K Gibran, Fadlin

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