A thorough understanding of the internal structures of the Longitudinal Valley is crucial for comprehending the architecture of the suture zone between the Eurasian and Philippine Sea plates. Here, we present the findings of eight new reflection seismic profiles spanning north to south of the Longitudinal Valley. Our primary objective is to investigate the internal sedimentary and tectonic features of the Longitudinal Valley Basin, the nature of the contact between it and the metamorphic basement rocks to the west, and the geometry of the Longitudinal Valley fault system along its eastern flank. A significant outcome of our research is that there is minimal internal deformation within the Longitudinal Valley Basin, with sedimentary features prevailing. The presence of inclined reflections suggests the presence of fan deltas and therefore a marine or lacustrine environment in the Longitudinal Valley. The sedimentary characteristics indicate that the source region for the sediment was predominately the Central Range, but that locally the Coastal Range also supplied sediment. Furthermore, at least in the shallow subsurface (1 to 2 km), a west-dipping Central Range fault does not exist along the western side of the Longitudinal Valley. The Longitudinal Valley fault system does not affect the middle of the basin, instead it is located along the eastern flank, adjoining the topography of the Coastal Range., Kuo-Chen and Brown wish to acknowledge grant NSTC 112-2811-M-002-006 for visiting researcher and grant MOST 104-2628-M008-005-MY3 for field work . Insightful reviews by L.S.-H. Lai, T. Byrne, and L. Kirstein helped focus and improve the paper. Field work assistances by C.-Y Wang, H.-Y. Kuo and Z.-K. Guan are highly appreciated. This publication if part of the I+D+i project PID2022-139422NB-I00 financed by MCIN/AEI/ 10.13039/501100011033 and by FEDER Una manera de hacer Europa., Peer reviewed

A first-order approximation of the lithological make-up of an orogen's middle and lower crust can provide insights into its structure, as well as the tectono-metamorphic and geodynamic processes taking place there. In this study, we investigate the possible lithological and chemical composition of Taiwan's middle and lower crust by matching in situ physical properties measured by the TAIGER tomography data with isotropic wavespeeds, density, and major element composition for a variety of upper amphibolite and granulite facies rocks modelled at ambient pressure and temperature using the AbersHacker Macro. The modelling suggests that Taiwan's middle crust is possibly comprised of some combination of biotite-poor metapelite, garnet-poor felsic granulite, mafic granulite, amphibolite, and marble. The lower crust is likely comprised of mafic granulite, garnet-rich felsic granulite, biotite-free metapelite, and eclogite. Furthermore, the modelling shows that the modal abundance of garnet and/or sillimanite has a significant effect on physical properties, elevating seismic wavespeeds and density of felsic rocks to those of mafic rocks. The modelled wt% major oxide composition suggests that Taiwan's middle and lower crust have a more mafic chemical composition than that of global compilations of the continental crust. Nevertheless, this reflects the choices made when assigning rock types for the lithological mix used to calculate the wt% oxides, since increasing the percentage of garnet-rich metapelite and felsic granulite would result in a more felsic bulk composition., This publication if part of the I + D + i project PID2022-139422NB-I00 financed by MCIN/AEI/ 10.13039/501100011033 and by FEDER Una manera de hacer Europa. Kuo-Chen and Brown wish to acknowledge visiting researcher grant NSTC 112-2811-M-002-006., Peer reviewed

The Meishan-Chiayi area of western Taiwan has a large probability of producing a major earthquake in the near future. Historically, one of the largest and most damaging of Taiwan¿s earthquakes occurred there. It is, therefore, important to have a well-constrained upper crustal 3-D shear-wave velocity model that can be used to accurately determine ground motion predictions and fault geometry models used in seismic hazard and risk modelling. In this study, we carried out an ambient noise tomography experiment using 100 seismometers deployed with a ~2 km spacing on a 20 by 20 km grid. The reliable periods of phase velocity from Rayleigh waves are 0.6 to 6.8 s, providing a well-resolved Vs structure from the surface to a depth of around 4 km. The velocity model displays a prominent, roughly northeast-striking change in Vs that follows the projected surface trace of the blind Chiayi thrust. The uplift of relatively higher Vs rocks in its hanging wall, together with a negative to positive change in dVs suggests that it dips gently eastward across the study area. A northward thickening of the lower Vs crust, together with a high negative dVs in the north of the study area is related to an increased thickness of foreland basin rocks across the Meishan fault. The Vs and dVs models provide reasonable evidence that the Meishan fault can be traced at a high angle from its surface rupture to the base of the model at 4 km depth. It cuts the Chiayi thrust., This project is supported by Ministry of Science and Technology (Grant No.: MOST 104-2628-M-008-005-MY3 and MOST 106-2119-M-008-006). Kuo-Chen and Brown wish to acknowledge visiting researcher grant NSTC 112-2811-M-002-006. Brown wishes to acknowledge I+D+i project PID2022-139422NB-I00 financed by MCIN/AEI/ 10.13039/501100011033 and by FEDER Una manera de hacer Europa, and a 2024 invited research professorship from National Central University. Discussion with Dr. F.C. Lin of Utah University is truly beneficial to the manuscript. S-wave tomography model presented in all figures can be obtained from the corresponding author Hao Kuo-Chen

20 pages, 8 figures, supporting information .-- Data Availability Statement: The seismic image data are available at the Zenodo repository (Xu et al., 2025). The code and relevant data are available at the Zenodo repository (Xu, 2025). The GEBCO 2024 Grid with a resolution of 15 arc-seconds is available at https://www.gebco.net/.Theseismiceventsthatoccurredbetween1900–2024arefromtheUSGSearthquakecatalog (https://earthquake.usgs.gov/). The parts of the maps are created using the open-source software Generic Mapping Tools (GMT) and MATLAB. The seismic profiles are processed and interpreted in Petrel software, Whether subducted seafloor topography can generate or inhibit large earthquakes is a long-standing debate, primarily due to the lack of three-dimensional constraints on megathrust morphology and frictional properties over large earthquake ruptures. The eastern Makran subduction zone is characterized by the subduction of the Little Murray Ridge and a strong segmentation in seismicity and large earthquake ruptures. By integrating 6,200 km of 2D seismic profiles and 50-m-resolution multibeam bathymetry with the critical wedge theory, we show that the ridge subduction has locally developed a rough plate interface, characterized by high apparent basal friction
(0.09–0.14), and significant yield stress variations, while the non-ridge segment exhibits a smooth plate interface, low
(0.06), and less yield stress variation. These distinct structural and mechanical properties effectively controlled the rupture behavior of the 1945 Mw 8.1 and 2017 Mw 6.3 earthquakes, which were both facilitated by the smooth plate interface, but halted upon encountering the rough segment. Moreover, the 1945 Mw 8.1 earthquake nucleated at a basement high front, where the
is elevated. This nucleation location, combined with the earthquakes rupture behavior, suggests that subducted topography can act as both an asperity and a barrier. To the best of our knowledge, the 1945 Mw 8.1 event is likely the largest instrumental event generated by a subducted topographic feature, contrasting with previously globally observed magnitude ∼7 events linked to rough asperities. Therefore, the earthquake potential associated with subducting topographic features has likely been underestimated in global active margins, and requires re-evaluation, This study was jointly supported by China-Pakistan Joint Research Center on Earth Science, Chinese Academy of Sciences, the National Natural Science Foundation of China (Number 42276222), the Development Fund of South China Sea Institute of Oceanology of Chinese Academy of Sciences (Numbers SCSIO202207, SCSIO2024QY02), the International Partnership Program of Chinese Academy of Sciences (Number 059GJHZ2024089FN), Chinese Academy of Sciences (Numbers 131551KYSB20200021, Y4SL021, E1SL3C02), the Hainan Foreign Expert Project (Number G20230607009E). Jonas Ruh was supported by I+D+i projects PID2022-139422NB-I00 and RYC2021-031331-I financed by MICIU/AEI/10.13039/501100011033, EU NextGenerationEU/PRTR, and FEDER EU, This work contributes to the Institut de Ciències del Mar "Severo Ochoa Centre of Excellence" accreditation CEX2024-001494-S funded by AEI 10.13039/501100011033 of the Spanish Ministry of Science and Innovation, Peer reviewed

14 pages, 9 figures, 1 table, supplementary materials https://doi.org/10.1016/j.epsl.2025.119645.-- Data availability: Data will be made available on request and supplementary materials (https://doi.org/10.20350/digitalCSIC/18154), The origin and evolution of the Martian dichotomy is one of the most enigmatic topics in Mars geological history. Its morphological variations suggest how it undergone different geological events, which reshaped the dichotomy differently. The eastern dichotomy, in the Nilosyrtis Mensae, is the only location where there is clear evidence of extensional structures in the highlands and parallel compressional structures in the adjacent southern lowlands. Both are roughly aligned parallel to the dichotomy and their origins are still debated. Here, we investigate the hypothesis that these faults are linked to gravity-driven deformation, occurred during the Late Noachian – Early Hesperian. Remote sensing geological mapping, integrated with 2D kinematic and numerical modeling, supports the possibility that extension in the highlands and along the dichotomy is kinematically linked to compression ∼800 km in the southern lowlands. The link occurs through a common basal detachment, which developed from the hard-link between a shallower frictional detachment in the highlands and a deeper viscous detachment in the lowlands. This hypothesis also provides insights into the origin and evolution of both the dichotomy and the lowlands, supporting the hypothesis of a giant Borealis northern impact. Such an impact promoted the formation of a magma pond followed by precipitation of evaporites from an ancient short-lasting shallow hypersaline sea, which was later reorganized by subsequent impacts and buried beneath volcanic deposits, JBR was funded by the projects RYC2021–031331-I and PID2022-139422NB-I00, financed by MICIU/ AEI/10.13039/501100011033, FSE+, and the European Union Next Generation EU/PRTR, This work contributes to the Institut de Ciències del Mar "Severo Ochoa Centre of Excellence" accreditation CEX2024-001494-S funded by AEI 10.13039/501100011033 of the Spanish Ministry of Science and Innovation, Peer reviewed

11 pages, 5 figures, 1 table, Active plate tectonics require weak boundaries that accommodate large strain over long time periods. Many studies argue that shear heating converted from dissipated mechanical energy may be responsible for the necessary weakening in the mantle lithosphere to initiate and sustain weak plate boundaries. Here, I present simple numerical simulations of pure olivine systems with a composite diffusion-dislocation creep rheology coupled to a selfconsistent grain-size evolution model to investigate the effect of grain-size reduction on shear heating. Results demonstrate that the weakening related to grain-size reduction and the activation of grain-size-sensitive diffusion creep undermines the importance of shear heating in mantle shear zones. Depending on shear zone width, shear velocity and apparent stresses, estimations on ideal shear zone widths and viscosities are presented, This work was supported by the projects RYC2021-031331-I, CNS2023-145755, PID2022-139422NB-I00 and CEX2024-001494-S, funded by MICIU/AEI/10.13039/501100011033, FEDER and European Union NextGenerationEU/PRTR, Peer reviewed

16 pages, 11 figures, 3 tables, In thrust wedges with multiple weak layers, individual décollements are generally thought to control only the structural vergence of the thrust systems directly above them. However, along the strike of the Zagros Simply Folded Belt, the structures above a common basal décollement at the Hormuz salt layer exhibit different vergence, including forward-, doubly-, and backward-vergent thrust wedges. Despite the importance of intermediate décollements for determining structural styles in the Zagros Simply Folded Belt, their effects on the structural vergence of the thrust system beneath them remain poorly understood. To address this issue, we conducted systematic experiments using discrete element models with a basal décollement on top of the basement and an intermediate décollement within the overlying strata. By varying the strength, thickness, and depth of the intermediate décollement, we successfully reproduced all types of thrust wedges (i.e., forward-, doubly-, and backward-vergent) in the thrust system beneath it. This suggests that intermediate décollements can determine the vergence of the thrust wedges beneath them. Moreover, our results reveal that specific combinations of intermediate décollement properties and shortening rates are crucial for the development of a backward-vergent thrust wedge in the thrust system beneath the intermediate décollement. This provides an alternative mechanism for the formation of such wedges. Together with geological and geophysical observations, we propose that intermediate décollements are responsible for along-strike vergence variations in the Zagros Simply Folded Belt. Thus, the interactions between thrust systems at various scales should be emphasized, This work was jointly supported by the National Natural Science Foundation of China (grant 42120104004), the Second Tibetan Plateau Scientific Expedition and Research Program (grant 2019QZKK0708), the National Natural Science Foundation of China (grant 42174112), and the Central Public-Interest Scientific Institution Basal Research Fund (grant CEAIEF2024030101, and CEAIEF2022030202). JBR was funded by the projects RYC2021-031331-I and PID2022-139422NB-I00, financed by MICIU/AEI/10.13039/501100011033, FSE+, and the European Union Next Generation EU/PRTR, This work contributes to the Institut de Ciències del Mar "Severo Ochoa Centre of Excellence" accreditation CEX2024-001494-S funded by AEI 10.13039/501100011033 of the Spanish Ministry of Science and Innovation, Peer reviewed

Laboratory measurements show that quartz-bearing rocks undergo a decrease in P-wave velocity when approaching the α–β quartz transition, followed by an abrupt increase afterwards. S-wave velocity changes only slightly. This change can have a signature in crustal geophysical data. Here, we use the AbersHackerMacro to explore how the modal abundance of quartz affects the Vp/Vs ratio and reflectivity across the α–β transition in a number of high-grade metamorphic rocks. The modelling shows that even with a low modal abundance of quartz, the α–β transition is recognisable in the Vp/Vs ratios of these rocks. α quartz has a strong influence on these Vp/Vs ratios, whereas β quartz does not. There is an increase in the reflection coefficient across the α–β transition with an increase in modal abundance of quartz. Reflection coefficients between different lithologies with less than about 25% quartz can increase or decrease. With greater than 25% quartz, reflection coefficients decrease., This work was supported by I+I+D+i project PID2022-139422NB-100 financed by MICIU/AEI/10.13039/501100011033 and by FEDER., Peer reviewed

29 pages, 14 figures, 2 tables, supporting information https://doi.org/10.1029/2025GC012681.-- Availability Statement: Software for this research is available through Zenodo as open access code with a Creative Commons Attribution 4.0 International license. The repository is available via Ruh (2026) https://doi.org/10.5281/zenodo.19097790, Continental collision is a key process in lithospheric evolution, driving mountain building, crustal thickening, and supercontinent assembly. Within the Wilson cycle, collision marks the final stage following rifting, ocean spreading, and subduction. Early rifting and rifted margin development precede basement accretion and hard continental collision, leaving complex records that complicate tectonic interpretations. We present mantle-scale numerical models simulating rifting, post-rift thermal re-equilibration, convergence, subduction, and collision. Results show that a strong continental crust produces narrow rifted margins, while a weak crust leads to margins with wider hyperextended domains. Subduction initiates beneath rifted continental margins due to inherited zones of reduced grain size. We assess the impact of syn-rift sediment rheology, erosion rates, and mantle serpentinization on non-magmatic rifted margin evolution, subduction and collision. Our findings indicate that rift-inherited architecture primarily controls basement accretion and collision style, more than surface processes or sediment rheology. Lithospheric shear zones with reduced grain size may serve as the location of subduction initiation. Comparisons with natural examples such as the Alps, Pyrenees, and Greater Caucasus support a first-order interpretation of their structural and mechanical evolution based on our models, JBR was supported by the projects RYC2021-031331-I, CNS2023-145755, PID2022-139422NB-I00 and CEX2024-001494-S, funded by MICIU/AEI/10.13039/501100011033, FEDER, and European Union NextGenerationEU/PRTR. PG was supported by the research project Structure and Deformation of Salt-bearing Rifted Margins (SABREM), PID2020-117598GB-I00, funded by MCIN/AEI/10.13039/501100011033, Peer reviewed