On May 26^th, 2006, the Mw 6.3 earthquake devastated the Yogyakarta region in a shallow strike-slip mechanism. Previous studies suggest the 2006 Yogyakarta earthquake aligned with the Opak river fault. However, several studies reported the aftershock distribution occurred along the eastward side of the Opak river fault strike. Those discrepancies may indicate two possibilities. First, the Opak river fault has an eastward dipping fault. Second, there are unidentified fault lines rather than Opak river fault. In this study, we investigated the fault segment that was responsible for the 2006 earthquake. We estimated the fault length based on seismic moment release assuming rigidity, fault depth, and coseismic displacement are 30 GPa, 12.5 Km, and 1 m, respectively. Therefore, we investigated the two possible scenarios using multi-years and recent Global Navigation Satellite System (GNSS) network developed by the Department of Geodetic Engineering, Universitas Gadjah Mada. The GNSS observation suggests the 2006 Yogyakarta earthquake occurred on the unidentified fault rather than has an eastward dipping fault. The estimated fault length is only 9.2 Km segment. Hence, the present study implies that other fault segments might not have released the accumulated stress and may become large earthquakes in the future.

We analyze the Global Positioning System (GPS)-derived strain rate distribution to investigate active crustal structure in Central Java, Indonesia, using ten years (2010–2019) continuous and permanent observation data. Central Java is the third-most populous province in Indonesia where postseismic deformation of devastating Yogyakarta earthquake in 2006 might influence the GPS data. The postseismic extensional response might overshadow the low contractional process due to active tectonics deformation. A decomposition method of a calculated strain rate shows a long wavelength feature with the extensional region in the vicinity of the 2006 Yogyakarta earthquake may reflect the postseismic process remain active. The short wavelength pattern is sharpening potential active tectonics dominated by oblique Northwest-Southeast dip-slip motion with East-West left-lateral sense. Our result demonstrates essential implications for assessing future seismic hazard potential within a low strain rate such as the Central Java region.

The back–arc thrust region in Eastern Java to Flores is significantly influenced by the arc–continent collision between the Australian Plate and the Eastern Sunda Arc, leading to a tectonic regime characterized by high seismic and volcanic hazards. This area has experienced several major earthquakes. However, back–arc thrust in Eastern Java remains absent from significant shallow earthquakes, which might indicate intense deformation. We conducted an analysis using recent and dense Global Navigation Satellite System (GNSS) observations from both continuous and campaign stations to develop a strain rate model and explore the detailed crustal behavior and strain accumulation within the Eastern Java back–arc thrust system. Our findings revealed varying values of compression and extension throughout the region, with compression values ranging from −2.24 to 0.086 μstrain/year. Additionally, we observed that the maximum shear strain rate and dilatation strain rate were within the ranges of 0.0013 to 1.12 μstrain/year and −2.24 to 0.698 μstrain/year, respectively. These findings could facilitate more informed strategies and improve preparedness for future seismic events.

This article evaluates the quality of the national 3-D positioning infrastructure using multi-criteria decision making (MCDM) to simulate the potential application of multi-GNSS method. The MCDM evaluation used coverage and availability of Indonesia Continuous Operating Reference System (INACORS) services, distribution of survey pillars, and accuracy of height determination using the Indonesian Geoid Model (INAGEOID). The term multi-GNSS method refers to the utilization of PPP method as a complement to the conventional differential GNSS method for the production of mapping control points. The results of this evaluation were complemented by a questionnaire analysis on the utilization of positioning infrastructure by respondents from various professional backgrounds. The MCDM evaluation results showed that Java had nearly 100% good or excellent 3-D positioning infrastructure quality. Other regions in Indonesia still had significant areas of average, fair, or even poor quality. The questionnaire results showed that many users have faced some problems in areas with fair or poor infrastructure quality. The application of multi-GNSS method can contribute to reduce up to half of the area with fair and poor positioning infrastructure quality.

Disaster risk in South Sulawesi, Indonesia, has increased owing to environmental degradation, population growth, and climate change. The employment of Early Warning Systems (EWSs) is fundamental to disaster risk reduction strategies aiming to provide timely and actionable information and thus minimize life loss and damage. This paper reviews EWS effectiveness in South Sulawesi, deploying a systematic disaster management approach that incorporates mitigation, preparedness, response, and recovery phases. Implementation gaps, community participation, technological infrastructure, institutional coordination, and local knowledge integration are analyzed through a literature-based review of academic articles, government documents, and case studies from 2015 to 2024. The review highlights the importance of multi-sector collaboration, proposing a more inclusive and localized approach to improve disaster resilience in South Sulawesi. It is demonstrated that EWS competence relies on the integration of community involvement and technological innovation, while effective communication in fostering trust and preparedness to address flood hazards is also highlighted.

The United Nations Convention on the Law of the Sea (UNCLOS) establishes a framework for coastal states to confirm their continental shelf beyond 200 nautical miles from baselines, often referred to as the Extended Continental Shelf (ECS). This procedure, outlined in UNCLOS Article 76, requires states to submit extensive scientific and legal documentation to the United Nations Commission on the Limits of the Continental Shelf (UN-CLCS). While the technical and legal aspects of ECS delineation have been widely studied, research focused on the process’s broader effects on geospatial governance and marine spatial planning (MSP) is limited. This study aims to examine how the ECS delineation process contributes to geospatial governance and provides a spatial foundation for marine spatial planning. This research addresses this gap by analyzing the executive summaries of 34 successful ECS submissions receiving formal UN-CLCS recommendations. Using qualitative content analysis, the study examines specific criteria states have employed, including their survey methods, data sources, and how they applied UNCLOS formulas and constraints. The data include bathymetric, geophysical, geological, and sediment thickness information from national and international sources. The findings show that bathymetric surveys are used in all submissions, with many states also applying both the Gardiner and Hedberg formulas while consistently adhering to the 350-nautical-mile and 100-nautical-mile-beyond-2,500-m-isobath constraints. The study also highlights the key role of current and former UN-CLCS members in providing expert advice to ensure submissions are scientifically sound and legally valid. Beyond technical aspects, the ECS submission process improves geospatial clarity, decreases jurisdictional uncertainty, and supports sustainable ocean governance.