Earth and Planetary Science Letters最新文献

{"title":"Frequency-dependent seismic radiation process of the 2024 Noto Peninsula earthquake from teleseismic P-wave back-projection","authors":"Kotaro Tarumi ,&nbsp;Kazunori Yoshizawa","doi":"10.1016/j.epsl.2025.119509","DOIUrl":"10.1016/j.epsl.2025.119509","url":null,"abstract":"<div><div>A large devastating earthquake of Mw 7.5 struck the Noto Peninsula, Japan, on January 1st, 2024. Persistent seismic swarms have preceded the main rupture around the hypocenter since 2020, likely driven by crustal fluids migrating upward from the lower crust. In this study, we investigated the frequency-dependent seismic radiation process using multi-frequency teleseismic P-wave back projection. The resulting source process reveals complex frequency-dependent behavior, which can be divided into four episodes. The initial episode lasts 15–20 s, characterized by high-frequency energy preceding low-frequency radiation. The second episode is marked by intense high-frequency P-wave emission with the absence of low-frequency signals. Then, intensive low-frequency P-waves are radiated from the source region, with ruptures propagating bilaterally from the hypocentral area toward the southwestern inland (third episode) and northeastern offshore (fourth episode) regions. The fluid-rich condition near the hypocenter likely plays an important role in controlling fault rupture, contributing to the observed complex rupture processes. The intricate fault geometry around the source region may have also contributed to the characteristic frequency-dependence of P-wave radiation during this earthquake.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119509"},"PeriodicalIF":4.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Disentangling global geochemical signals from local diagenetic alteration in shallow-water marine carbonates during OAE1a","authors":"Matthew D. Nadeau ,&nbsp;Jack G. Murphy ,&nbsp;Cedric J. Hagen ,&nbsp;Ziman Wu ,&nbsp;Alliya A. Akhtar ,&nbsp;Anne-Sofie Ahm ,&nbsp;Daniel A. Stolper ,&nbsp;Adam C. Maloof ,&nbsp;John A. Higgins","doi":"10.1016/j.epsl.2025.119513","DOIUrl":"10.1016/j.epsl.2025.119513","url":null,"abstract":"<div><div>Shallow-water marine carbonates are widely used to reconstruct short-lived (∼ million years) perturbations to global geochemical cycles (e.g., carbon, calcium, strontium, and lithium). However, local environmental phenomena like meteoric and marine diagenetic alteration or changes in carbonate facies often decouple carbonate geochemistry from open-ocean seawater chemistry. To accurately reconstruct global geochemical cycles using shallow-water carbonates, it is therefor crucial to separate signals of local environmental phenomena from genuine changes in open-ocean seawater chemistry. The well-documented shallow-water carbonate succession from Ocean Drilling Program Site 866A (Resolution Guyot, Mid-Pacific Mountains) offers an opportunity to disentangle global and local signals recorded in shallow-water carbonates during the Early Cretaceous oceanic anoxic event 1a (OAE1a), a brief, globally correlative perturbation to the carbon cycle. Recent studies at this site have documented a δ¹³C excursion, a modest decline in ⁸⁷Sr/⁸⁶Sr, and large stratigraphic variability in δ⁷Li and δ⁴⁴Ca values, all of which have been interpreted as reflecting temporal changes in the chemical composition of open-ocean seawater associated with OAE1a. However, other work at this site demonstrates clear evidence of meteoric and marine diagenesis as well as changes in carbonate facies across the OAE1a interval. Here, we aim to disentagle signals that reflect global geochemical cycling from those that reflect local environmental phenomena by employing a suite of carbonate-bound geochemical proxies (δ⁷Li, δ¹³C, δ¹⁸O_carb, δ²⁶Mg, δ⁴⁴Ca, Δ₄₇, [Mg], [Ca], [Sr], [Li]) and a numerical model of carbonate diagenesis. We show that while changes in ⁸⁷Sr/⁸⁶Sr ratios at this site reflect changes in primary seawater composition, stratigraphic variability in other geochemical systems (e.g., δ⁷Li, δ²⁶Mg and δ⁴⁴Ca values and trace element concentrations) arises primarily from early marine and meteoric diagenesis, with some contamination of Li from co-occurring clays. With much of the chemostratigraphic variability preserved today conceivably owing its origin to carbonate diagenesis and in recognition of the residence times for these elements in seawater (&gt;1 million years) being longer than the short-lived OAE1a event, we make a case that our model-derived “snapshot” estimate for the calcium, magnesium, and lithium isotope composition of the marine diagenetic fluid reflects a stable open-ocean Early Cretaceous seawater signature. Although a global δ¹³C signal may still be present, our findings show how the stratigraphic record of δ¹³C values across the OAE1a at this site is a complex function of marine and meteoric diagenesis and changes in carbonate facies.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119513"},"PeriodicalIF":4.8,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of late accretion impacts on an argon-constrained crustal growth model","authors":"Coral K. Chen ,&nbsp;Meng Guo ,&nbsp;Jun Korenaga ,&nbsp;Simone Marchi","doi":"10.1016/j.epsl.2025.119493","DOIUrl":"10.1016/j.epsl.2025.119493","url":null,"abstract":"<div><div>As an important reservoir for incompatible elements, the growth of the continental crust profoundly influenced the composition of the mantle and the atmosphere. The co-evolution of the continental crust, mantle, and atmosphere throughout Earth history can be traced through the transfer of argon and potassium between these three reservoirs. While many argon-constrained crustal growth models have been proposed, none of them consider the effect of late accretion (bombardment by leftover planetesimals in the several hundred million years after the Moon formed) in detail. Our model is the first of its kind to simulate both the volatile delivery and the atmospheric erosion by impacting planetesimals. Whereas the relative fraction of impactor-derived argon in the present-day atmosphere depends on the assumed impactor composition and the starting atmospheric mass, the present-day atmospheric argon originates largely from mantle degassing and crustal processing. For a range of impact parameters, our model results indicate that the early rapid growth of continental crust is required to satisfy the argon budget of the mantle and atmosphere.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119493"},"PeriodicalIF":4.8,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144313730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bridging fault kinematics before, during, and after the 2022 Menyuan earthquake","authors":"Rumeng Guo ,&nbsp;Wenting Zhang ,&nbsp;Xiongwei Tang ,&nbsp;Kun Dai ,&nbsp;Yu Li ,&nbsp;Dechuan Liu ,&nbsp;Yong Zheng ,&nbsp;Shiyu Zeng ,&nbsp;Jiangcun Zhou ,&nbsp;Jianqiao Xu ,&nbsp;Heping Sun","doi":"10.1016/j.epsl.2025.119510","DOIUrl":"10.1016/j.epsl.2025.119510","url":null,"abstract":"<div><div>Decoding both surface deformation and underlying fault kinematics is of great significance for understanding earthquake physics and assessing seismic hazards. Herein, we compile the interseismic, coseismic, and postseismic InSAR deformation from 2014 to 2022 associated with the 2022 Ms 6.9 Menyuan earthquake and decipher the underlying creeping rate, seismic rupture, and stress-driven afterslip. Our results show that the dynamic rupture of the Menyuan event is precluded on the west by a creeping section and on the east by a highly locked section, which may be a stress barrier with high seismic potential. Its coseismic slip is mainly distributed within the high-coupling patch, and the afterslip occurred dominantly downdip of the coseismic asperity, an area also characterized by interseismic creeping, in line with the slip pattern predicted by the rate-and-state frictional framework. Afterslip and aftershocks are concentrated in regions of positive Coulomb failure stress changes (ΔCFS) due to the coseismic slip, and the increased ΔCFS is released &gt;70 % aseismically and &lt;30 % seismically by aftershocks. Finally, we introduce a conceptual model for this seismogenic fault to describe fault behaviors as well as frictional properties during the earthquake cycle. This study contributes valuable insights into the slip evolution, slip budget, and frictional behaviors of continental strike-slip fault systems.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119510"},"PeriodicalIF":4.8,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144313733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High 3He/4He plumes are hotter and melt more: evidence from the petrology and geochemistry of ocean island basalts","authors":"Sunna Harðardóttir,&nbsp;Matthew G. Jackson","doi":"10.1016/j.epsl.2025.119490","DOIUrl":"10.1016/j.epsl.2025.119490","url":null,"abstract":"<div><div>High ³He/⁴He (i.e., ³He/⁴He above the convecting upper mantle mid-ocean ridge basalt range (8 ± 2 R_A)) is a rare component identified in hotspots that sample an early-formed, less-degassed domain in the planet. Relationships between the maximum ³He/⁴He and high hotspot buoyancy flux, and between maximum ³He/⁴He and low seismic shear-wave velocity anomalies, suggest that high ³He/⁴He is entrained only by the hottest and most buoyant mantle plumes. A prediction of this model is that the high ³He/⁴He component is sampled by high-degree melting. We use a new geochemical database of ocean island lavas to demonstrate that high ³He/⁴He is found only in tholeiitic (low alkali index) and mildly alkalic (intermediate alkali index) lavas, which result from high and moderate degrees of melting, respectively. Highly alkalic (high alkali index) lavas that are generated by low degrees of melting are not observed to have very high ³He/⁴He. These observations support a model where the highest ³He/⁴He plumes are the hottest and therefore melt to high degrees, which results in generation of tholeiites and mildly alkalic lavas. However, our observations suggest that high degrees of melting of hot plumes is a necessary but insufficient condition for generation of high ³He/⁴He lavas. High degrees of melting of mantle domains with a high fraction of recycled material and/or depleted mantle material—both of which have low ³He/⁴He—will generate low ³He/⁴He lavas. Thus, only hot melting of mantle domains that have relatively pure high ³He/⁴He source material (i.e., little or no recycled material or depleted low ³He/⁴He mantle material) will result in generation of high ³He/⁴He lavas. The conclusion that high ³He/⁴He plumes melt more is supported by geophysical observations that suggest high ³He/⁴He plumes are hotter—they have higher buoyancy flux and lower shear-wave velocity anomalies in the upper mantle—and hotter plumes should melt more than cooler plumes.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119490"},"PeriodicalIF":4.8,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining water dynamics through unsaturated and saturated zones using fiber-optic seismic sensing data","authors":"Junzhu Shen,&nbsp;Tieyuan Zhu","doi":"10.1016/j.epsl.2025.119507","DOIUrl":"10.1016/j.epsl.2025.119507","url":null,"abstract":"<div><div>Understanding the movement of water from the land surface through the vadose zone into groundwater is critical for studying the hydrologic cycle and predicting the Earth’s critical zone response to extreme weather events. While recent research has shown that seismic velocity changes are largely linked to the groundwater variation, the role of vadose zone water and its interactions with groundwater has often been overlooked. Here, we use high-density seismic sensors by employing distributed acoustic sensing (DAS) with fiber-optic cables to estimate seismic surface wave phase velocity variations. This allows us to constrain annual water dynamics in both unsaturated and saturated zones. We incorporate rock physics modeling to analyze shear wave velocity variations, to identify key physical parameters - such as saturation, pressure, and fractures - that best describe the water movement in response to rainfall. Our findings reveal that changes of pore pressure and saturation in the unsaturated zone resulting from precipitation influence high-frequency velocity changes. In the saturated zone, dynamic pore pressure induced by groundwater levels and crack opening or closure are primarily drivers for low-frequency velocity changes. Additionally, we observe the hysteresis in velocity variations between drying and wetting cycles over different time periods, implying fluid redistribution in pores and crack opening or closure responding to drying and wetting processes. Our findings have important implications of using DAS with existing fiber-optic cables for understanding how the critical zone responds to future climate events, such as extreme weather conditions like rainstorms and drought.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119507"},"PeriodicalIF":4.8,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144306248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controls on uranium isotope fractionation in the late Paleoproterozoic ocean","authors":"Alexandra Kunert ,&nbsp;Simon W. Poulton ,&nbsp;Donald E. Canfield ,&nbsp;Philip W. Fralick ,&nbsp;Geoffrey J. Gilleaudeau ,&nbsp;Brian Kendall","doi":"10.1016/j.epsl.2025.119498","DOIUrl":"10.1016/j.epsl.2025.119498","url":null,"abstract":"<div><div>Uranium isotope data from Proterozoic carbonates (δ²³⁸U_carb) and black shales (δ²³⁸U_auth) are enigmatic. Average Proterozoic δ²³⁸U_carb (approximating Proterozoic seawater, δ²³⁸U_sw) is similar to modern river/seawater δ²³⁸U, and Proterozoic black shales do not always record highly fractionated δ²³⁸U_auth compared to contemporaneous δ²³⁸U_carb. However, very light δ²³⁸U_carb and heavy δ²³⁸U_auth for the widely anoxic Proterozoic oceans was expected because large isotope fractionations accompany U reduction in anoxic environments. To address this enigma, we report black shale δ²³⁸U_auth through a well-characterised multi-core transect in the late Paleoproterozoic Animikie Basin, North America. There is a wide range of δ²³⁸U_auth, from –0.52‰ to 0.53‰, that generally correlates with organic carbon enrichments. Heavy δ²³⁸U_auth in organic-rich shallow shelf sediments within and near a euxinic wedge are attributed to enhanced productivity with vigorous sediment microbial activity, neutrally charged aqueous U species that slow reaction kinetics, and redoxcline fluctuations. In less organic-rich sediments of the anoxic-ferruginous deep shelf environment, characterized by lower productivity and plentiful reduced iron availability, light δ²³⁸U_auth may reflect rapid U reduction or adsorption to solid Fe/Mn species. Hence, for the widely anoxic Proterozoic oceans, we propose that large isotopic fractionations (0.4 to 1.2‰) were associated with highly productive areas on anoxic continental margins, and muted isotopic fractionations (–0.1 to 0.4‰) occurred in anoxic deep-ocean environments. Low-productivity Proterozoic oceans yielded sediments with δ²³⁸U_carb and δ²³⁸U_auth close to modern river/seawater values, whereas higher-productivity basins (e.g., Animikie Basin) resulted in lower δ²³⁸U_carb and more variable δ²³⁸U_auth.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119498"},"PeriodicalIF":4.8,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144313731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbonation and deformation of oceanic serpentinites in the Elba subduction channel: Evidence for fluid–rock interaction at seismogenic depth","authors":"Samuele Papeschi ,&nbsp;Roberto Emanuele Rizzo ,&nbsp;Andrea Rielli ,&nbsp;Matthew Tarling ,&nbsp;Vanni Moggi Cecchi ,&nbsp;Elena Pecchioni ,&nbsp;Chiara Boschi ,&nbsp;Keishi Okazaki ,&nbsp;Takehiro Hirose ,&nbsp;Paola Vannucchi","doi":"10.1016/j.epsl.2025.119488","DOIUrl":"10.1016/j.epsl.2025.119488","url":null,"abstract":"<div><div>We present a multi-disciplinary investigation of the deformation and carbonation history of oceanic serpentinites involved in the plate interface of the Cretaceous-Eocene subduction complex exposed in the Elba Island —an exceptionally well-preserved example of oceanic subduction system. Using an integrated set of structural, petrographic, and geochemical analyses, we document antigorite growth and carbonation of oceanic serpentinites in the Elba subduction channel at shallow-intermediate depths (&lt;22-26 km; P &lt;0.6-0.7 GPa). Carbonation was associated with brecciation and shearing that produced a complex of tectonic slices (Norsi area) and a tectonic mélange (Cavo area). The carbonation process was likely triggered by the release of CO₂-rich fluids from subducting oceanic serpentinites and ophicarbonate rocks, as indicated by C and O isotopes. The ingress of external CO₂ in shear zones likely ignited a positive feedback between deformation, carbonation, and fluid flow, promoting talc formation and leading to strain localization at the plate interface. The Elba subduction channel offers a unique window on the evolution of subduction systems at low pressure, highlighting the importance of fluid-induced reactions in controlling deformation style.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119488"},"PeriodicalIF":4.8,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144306234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isotopically heavy molybdenum burial in oxic pelagic sediments and implications for paleo-redox reconstruction","authors":"Jianlin Liao ,&nbsp;Zhiyong Lin ,&nbsp;Xiaoming Sun ,&nbsp;Yinan Deng ,&nbsp;Alain Manceau ,&nbsp;Olivier Mathon ,&nbsp;Guoqing Zhao ,&nbsp;Andrea Koschinsky ,&nbsp;Florian Scholz","doi":"10.1016/j.epsl.2025.119497","DOIUrl":"10.1016/j.epsl.2025.119497","url":null,"abstract":"<div><div>Molybdenum (Mo) concentrations and isotopic signatures (δ⁹⁸Mo) are useful proxies for reconstructing paleo-redox conditions and tracing material cycling in subduction systems. While the Mo isotope geochemistry of diverse geological settings has been extensively studied over the past two decades, the diagenetic effects on Mo behavior in pelagic oxic sediments remain poorly understood. Here, we investigate Mo cycling in Mn-rich pelagic sediments in an 847 cm long sediment core from the deep Pacific Ocean. We observe a systematic downcore decrease in Mo content (28.0 to 6.10 μg/g) together with increasing Mo isotope ratios (δ⁹⁸Mo: −0.52 ‰ to +1.32 ‰). Synchrotron X-ray absorption spectroscopy shows that the average oxidation state of Mn decreases with depth, which is consistent with the transformation of Mn minerals during sediment burial. In contrast to the canonical δ⁹⁸Mo (−0.7 ‰) of Fe-Mn nodules and crusts, the depth-integrated δ⁹⁸Mo value of the Mn-rich sediments is unusually high, likely due to recycling of isotopically light Mo. If our findings are representative for larger areas of the deep ocean, they could potentially challenge the conventional global Mo budget. A revised isotopically heavier oxic Mo sink in the global ocean’s Mo budget would imply a more extensive expansion of oceanic anoxia and/or reduction of the oxic sink during geological periods when seawater had lower δ⁹⁸Mo values.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119497"},"PeriodicalIF":4.8,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144306233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Imaging viscosity after the 2021 Mw 7.4 Maduo earthquake: Insights on the regional rheology variation beneath the Bayan Har block","authors":"Zhen Li ,&nbsp;Wei Xiong ,&nbsp;Andrew Hooper ,&nbsp;Zeyan Zhao ,&nbsp;Yuan Gao ,&nbsp;John R. Elliott ,&nbsp;Tim J. Wright ,&nbsp;Han Yue ,&nbsp;Teng Wang","doi":"10.1016/j.epsl.2025.119465","DOIUrl":"10.1016/j.epsl.2025.119465","url":null,"abstract":"<div><div>The rheology of Earth's lithosphere fundamentally governs tectonic processes and landscape evolution. Postseismic deformation following large earthquakes has been widely used to constrain rheological structures globally. However, regional-scale rheological variations remain poorly understood due to the infrequency of large earthquakes. The Bayan Har Block in the central-eastern Tibetan Plateau is a unique tectonic unit to investigate rheology regional-variations by pronounced high seismicity, heat flow anomalies, and localized lithospheric thinning. Here, we image postseismic deformation following the 2021 Maduo earthquake using InSAR and GNSS observations to probe the rheology over the block’s north-east margin. We integrate long-term and short-term interferograms to separate deformation from atmospheric signals. After accounting for interseismic velocity, InSAR measurements extends out to 200 km from the rupture and its tips. Compared with prior studies, higher-quality far-field measurements allow the separation of viscoelastic relaxation from near-field afterslip effects. Our preferred model indicates a Burgers (bi-viscous) lower-crust rheology with transient and steady-state viscosities of 2.5 (+2.5/-1.3) × 10¹⁸ Pa·s and 2.5 (+0.7/-0.5) × 10¹⁹ Pa·s, respectively, beneath a 20-km-thick elastic layer. By testing laterally-variable and depth-dependent rheological structures, we identify a smaller intraplate-to-interplate viscosity contrast (factor of ∼2) than that observed after the 2008 Wenchuan (factor of ∼10) and 2001 Kokoxili (factor of ∼5) earthquakes. This result suggests a positive correlation between viscosity contrasts, fault slip rates, and topographic gradients at a regional scale. These findings highlight that the rheological contrasts within the Bayan Har block exert a fundamental control on the long-term topographic evolution of the central Tibetan Plateau.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"666 ","pages":"Article 119465"},"PeriodicalIF":4.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}