Deep-ocean drilling to explore the hydraulic structure of subduction faults
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Rare ice-base temperature measurements in Antarctica reveal a cold base in contrast with predictions
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Thermochronological markers reveal Late Cretaceous strike-slip faulting in the Yangtze Block, South China
Detecting strike-slip tectonics using thermochronology is challenging because the complex relative motion between fault blocks often does not substantially displace the vertical stratigraphy provided by thermochronological ages. Here we investigate the strike-slip tectonics in the Yangtze Block, South China, based on an original conceptual model and the zircon (U-Th)/He (ZHe) analysis of 17 sandstone samples. We exploit as a marker the northwestward trend of progressively decreasing ZHe ages generated by Mesozoic northwestward shortening. The ZHe age trend is broken by evident steps, which are also found in other published thermochronological datasets. We interpret these age steps as marking a previously undetected Late Cretaceous left-lateral strike-slip fault which intersects with prior deformation-propagation direction. Our approach to detect strike-slip faults confirms a major change in the subduction direction of the Paleo-Pacific Plate beneath Eurasia during the Late Cretaceous, and can find applications to other regions where thermochronological ages define suitable dipping markers.
Active ice sheet conservation cannot stop the retreat of Sermeq Kujalleq glacier, Greenland
Active conservation of an ice sheet seeks to reduce ice sheet mass loss and sea level rise. Here we explore the response of Sermeq Kujalleq in Greenland to limiting warm water inflow to the fjord it terminates by raising the sill by an artificial barrier at its mouth. We asynchronously couple an ice sheet model with a fjord model, and simulate glacier evolution with varying climate scenarios from the year 2020 to 2100. The tallest barrier cools the fjord water and reduces melt at the ice front. But this has minor impacts on glacier retreat under SSP5-8.5 and SSP2-4.5. Cooling the atmospheric forcing to 1990s levels reduces glacier retreat, but even reducing water temperatures with a barrier cannot stabilize the glacier. The glacier seems to be in an unstoppable phase of marine ice sheet instability on a rapidly deepening retrograde sloping bed and in water much deeper than in 2000s.
The 11-month precursory fault activation of the 2019 ML 5.6 earthquake in the Weiyuan shale gas field, China
Anthropogenic activities such as hydraulic fracturing (HF) can trigger destructive earthquakes, the triggering mechanisms of which are still in debate. We utilize near-fault seismic recordings to study the preparatory phase of the 2019 ML 5.6 earthquake in the Weiyuan shale gas field (WSGF), Sichuan Basin, China, which struck 3 months after stimulation completion. This is one of the largest HF-triggered earthquakes worldwide. We observed an 11-month-long precursory fault activation, during which continuous seismicity illuminated the fault plane and provided warnings for a potential destructive earthquake. The fault activation is a consequence of injections in multiple HF well pads, with a variety of mechanisms at play. Numerical simulation reveals that the occurrence of the mainshock involves stress perturbation from post-injection aseismic slip. This work promotes our understanding of HF-induced earthquakes and suggests incorporating long-term near-fault observations and taking post-injection aseismic slip into account for effective hazard management.
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