Sylvain Barbot

Urban land subsidence driven by groundwater extraction is widespread, but the processes governing how groundwater recovery translates into spatially variable surface uplift remain poorly understood. We use satellite geodesy and multi-decadal groundwater observations to measure vertical land motion in Greater Osaka, Japan, where aquifers are intersected by a dense network of crustal faults. We observe widespread surface uplift at rates up to 12 mm/year, organized into distinct domains separated by sharp boundaries. Uplift rates vary abruptly across domain boundaries, which coincide with mapped faults. Where no faults are mapped, abrupt spatial changes in uplift rate suggest the presence of previously unrecognized buried faults. Uplift rates are positively correlated with groundwater-level rise in wells screened at depths up to 600 m, while deformation modelling indicates dominant uplift sources are shallower than 500 m. Our analysis suggests crustal faults act as hydraulic barriers to lateral groundwater flow, localising vertical land motion during aquifer recovery, with implications for groundwater management, infrastructure stability, and land-use planning in urban basins worldwide.

The American Geophysical Union (AGU) announces the new living collection “Impactful Datasets in Earth, Space, and Environmental Sciences” which recognizes the creation and curation of datasets enabling research, analysis, and decision making beyond what is captured by traditional academic impact metrics. The collection highlights datasets through the dimensions of People, Planet, and Prosperity, and includes a curated set of nominated datasets and accompanying special collection of data papers. Developed with the Earth Science Information Partners (ESIP) community, the nomination and review process initially invites contributors from across research, operations, and public service, to nominate datasets important to their work, and then submit a data paper that expands upon the nomination text for inclusion in the special collection. This commentary highlights the rationale for the living collection, and the process of nomination. The collection serves as a living reference that strengthens data culture, supports reproducible geoscience, and provides enduring access to critical information for science and society.

Crustal faults across geological settings are often enriched in phyllosilicates because of the hydrothermal alteration of wall rocks. The frictional behavior of these altered rocks at mid-crustal conditions remains poorly understood. Here, we show that mica-schist gouge under crustal hydrothermal conditions can host mixed behavior promoting shallow aseismic creep and confined seismic ruptures. We conduct triaxial deformation experiments on natural samples from the East Anatolian Fault, Turkey, and simulate the resulting dynamics on the Pütürge segment during seismic cycles using a physical model of rock friction and a realistic thermal structure. Mica schist exhibits potentially unstable weakening between 300° and 400°C, promoting depth-confined earthquakes. The frictional properties of mica schist are compatible with the 2020 moment magnitude ( M _w ) 6.8 Elazığ earthquake and the northern rupture arrest of the 2023 M _w 7.8 Kahramanmaraş event, illustrating how the thermal and lithological structure affects rupture style and segmentation.

The structurally simple Sagaing fault, which ruptured during the 2025 moment magnitude 7.7 Mandalay earthquake, exhibits clear dynamic segmentation despite lacking major geometric complexities. Using physics-based seismic cycle simulations, we tested the hypothesis that dynamic segmentation on the Sagaing fault is influenced by a northward increase in long-term slip rates from 18 to 28 millimeter/year. Models incorporating geodetically constrained long-term slip rates reproduced the rupture extent of historical earthquakes and the geodetically inferred slip distribution of the 2025 mainshock. Slip rate contrasts of 10 to 20% between adjacent segments generate sufficient heterogeneous stress accumulation to initiate dynamic segmentation, regulating earthquake recurrence patterns and maximum magnitudes across the fault system. These results highlight the value of integrating geodetic, geological, and seismological observations to improve seismic hazard assessment.

Giant megathrust earthquakes typically occur above the upper-plate Moho or the 350°C isotherm in warm subduction zones. However, large earthquakes also occur within the mantle wedge corner at 35-55 km depth at cold subduction zones, such as the Kermadec, Japan Trench, and Chilean margins. Here we investigate the frictional behavior of lawsonite blueschist metagreywacke, potentially found in cold subduction channels, to better understand the control of metamorphic grade on such first-order variations in seismogenic depth. We perform velocity-step experiments on metagreywacke gouge from room temperature to 500°C and effective normal stresses from 50 MPa to 320 MPa, capturing the unstable friction regime and the brittle-to-flow transition. The constitutive behavior of metagreywacke indicates a potential seismogenic behavior at high temperatures below the Moho. Large megathrust earthquakes in the mantle wedge corner may develop in the lawsonite blueschist metasediment channel of cold subduction slabs.

The Red River Fault (RRF) presents a significant seismological paradox: its northern segment hosts frequent large earthquakes, whereas its southern segment remains largely quiescent despite similar tectonic loading. To investigate how fault-zone structure and frictional properties govern this seismicity contrast, we sampled outcrops where mylonitic shear zones host multiple layers of cataclasite within the fault core. In the northern segment, the mylonites are dominated by quartz and feldspar, by contrast, the mylonite is hornblende rich in the southern segment. Hydrothermal friction experiments are then conducted on the sampled mylonite and cataclasite fault rocks at 100–500 °C, fluid pressures of 50–100 MPa, and confining pressures of 150–200 MPa, approximating upper-midcrustal earthquake nucleation conditions.Our experimental results reveal a critical rheological contrast between the two segments. In the aseismic southern segment, the fault core cataclasites exhibit a transition to velocity weakening at intermediate temperatures; however, the surrounding mylonitic host rocks display stable velocity strengthening behavior across nearly the entire temperature range. Conversely, mylonitic host rocks from the seismically active northern segment exhibit unstable velocity weakening behavior over a wide temperature range of 150–500°C. Based on the architecture of the fault and numerical modeling, we propose that the frictional stability of the surrounding mylonitic rock acts as a rheological gate for earthquake propagation. In the south, although nucleation may initiate within the relatively weak and velocity-weakening cataclasite (μ=0.53-0.62), the contrasting stable response of the surrounding mylonite acts as a damper, arresting rupture and suppressing large events. In the north, the unstable velocity-weakening nature of the host rock promotes a "runaway" rupture process, amplifying nucleation events into large earthquakes. These results challenge models focused only on single fault rock properties, highlighting how host-rock rheology modulates seismic hazard along major continental faults.