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The Sumatran Fault Zone (SFZ) of the Indonesian island of Sumatra, which is broken up into 19 fault segments, accommodates much of the trench-parallel component of the oblique convergence between the Indo-Australian and Sunda plates. To understand the potential hazard of SFZ earthquakes to the local population, we investigate slip rates and locking depths of three SFZ segments in southern Sumatra using previously unpublished data from our Sumatran Fault Monitoring (SuMo) campaign Global Positioning System (GPS) network. We model the GPS data using a 2-D interseismic dislocation model optimized using a Bayesian approach. For the Musi segment of the SFZ, we find that slip rates ranging from 10 to 22 mm yr−1 and locking depths from 1 to 20 km fit the data similarly well, suggesting a lack of resolution for the SuMo network in this segment. For the Manna and Kumering segments where the resolution is better, the estimated slip rates are 18 [12–22, 95 per cent confidence intervals] mm yr−1 and 12 [9–15] mm yr−1, respectively, while the estimated locking depths are 29 [15–47] km and 5 [3–16] km, respectively. The deep locking depth estimated for the Manna segment can be explained by the large station gap in this segment. Considering the uncertainty, all the estimated slip rates from our study remains aligned with the SFZ's average slip rate of ∼15 mm yr−1, which was previously derived using updated geological slip rates and geodetic block modelling of the entire SFZ. Our results support the idea that the forearc sliver west of the SFZ behaves as a rigid microplate. [ABSTRACT FROM AUTHOR]

This study investigated the correlation between fault kinematics, surficial displacement, and surface rupture geometry patterns between earthquake cycles using particle image velocimetry (PIV) analysis of an analogue sandbox modeling that mimics InSAR observations. The research explored various fault systems, including reverse, normal, and strike-slip faults, through controlled sandbox experiments. The fault surface rupture zone manifests itself due to strain accumulation between two mobile blocks. The displacement magnitude is most pronounced on the surface and is absorbed by the section above the hanging wall or moving block. During fault surface rupture formation, the leading edge of the surface movement consistently extends beyond the anticipated fault surface rupture zone and retreats upon full fault surface rupture development. Subsequently, the distribution of the surface movement is sharply confined by the established fault surface rupture. The key findings of this study underscore the potential of PIV of sandbox modeling for studying fault surface rupture geometry and its development, providing insight into seismic processes. Overall, this work contributes to advancing our knowledge of seismic phenomena and improving strategies for earthquake prediction and mitigation. [ABSTRACT FROM AUTHOR]

The multidisciplinary study of Gunung Padang has revealed compelling evidence of a complex and sophisticated megalithic site. Correlations between rock stratifications observed through surface exposures, trenching and core logs, combined with GPR facies, ERT layers, and seismic tomograms, demonstrate the presence of multi‐layer constructions spanning approximately 20–30 m. Notably, a high‐resistive anomaly in electric resistivity tomography aligns with a low‐velocity anomaly detected in seismic tomography, indicating the existence of hidden cavities or chambers within the site. Additionally, drilling operations revealed significant water loss, further supporting the presence of underground spaces. Radiocarbon dating of organic soils from the structures uncovered multiple construction stages dating back thousands of years BCE, with the initial phase dating to the Palaeolithic era. These findings offer valuable insights into the construction history of Gunung Padang, shedding light on the engineering capabilities of ancient civilizations during the Palaeolithic era. [ABSTRACT FROM AUTHOR]

Earthquake doublets have been described in fault systems around the world but have not yet been confidently resolved in paleoseismic records. Our current knowledge is limited to historical occurrences, preventing researchers from uncovering potential patterns or recognizing common fault behavior. Identification of prehistoric doublets is thus of crucial importance for adequate seismic hazard assessment and risk mitigation. We developed a new methodology to reveal the sedimentary imprint of earthquake doublets in lacustrine paleoseismic records based on flow direction analysis in multipulsed turbidites, because the delayed arrival of turbidity currents originating from the same source location demonstrates the occurrence of individual triggering mechanisms. As grains tend to align in the presence of a flow, we analyzed flow directions by determining the dominant orientation of elongated grains using a combination of grain size, paleomagnetism, and high-resolution X-ray computed tomography. This methodology was applied to a turbidite deposited by the 2007 CE earthquakes in West Sumatra (Mw 6.4 and 6.3, 2 h apart), and it provides the first unmistakable sedimentary evidence for an earthquake doublet. We argue that this methodology has great potential to be applied to multipulsed turbidites in various subaquatic paleoseismic records and can reveal the occurrence of unknown earthquake sequences. [ABSTRACT FROM AUTHOR]