Earth and Planetary Science Letters最新文献

{"title":"Water ice particles detected by SELENE's Spectral Profiler at lunar shadowed regions in various local times and latitudes","authors":"Kosei Toyokawa ,&nbsp;Junichi Haruyama ,&nbsp;Takahiro Iwata ,&nbsp;Hitoshi Nozawa","doi":"10.1016/j.epsl.2024.119065","DOIUrl":"10.1016/j.epsl.2024.119065","url":null,"abstract":"<div><div>Processes of water (OH and H₂O) migration on the Moon remain unclear, prompting active research. Understanding lunar water migration requires investigation of the trapping and diffusion properties of water at various latitudes and local times. This study analyzed visible to near-infrared spectral data obtained by the Spectral Profiler (SP) onboard SELENE for shadowed regions at various local times and latitudes, not limited to the polar permanently shadowed regions. We assessed SP data for shadowed regions in 60 areas, each spanning a 10° × 10° latitude–longitude grid. Of the 1,061,907 analyzed shadowed-region data, 41,385 at various latitudes exhibited significant absorption in the 1.25 and 1.5 µm bands, indicating water ice particles. Data with the two absorption features suggest the presence of a water ice frost layer covering the lunar surface or suspended water ice particles above the lunar surface, at various latitude shadowed regions. Our spectral simulations have quantified the ice particles as being 0.1–1 µm in diameter, with a column density of 10^–4–10^–3 kg/m². The spectral parameters for band absorption at the 1.5 µm band show symmetry between morning and evening sides, which is potentially attributed to the absence of variations in ice grain size and quantity. The 1.5 µm band absorption shows an increasing trend toward terminator regions, indicating variation in the water ice distribution and likely reflecting temperature conditions for water retention. The latitudinal trend of ice grain size and quantity remains uncertain because of the observed noise levels. Observations of water ice particles in shadowed regions at various latitudes and local times can provide new constraints on trapping and diffusion processes of lunar water migration.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119065"},"PeriodicalIF":4.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing hydrous eclogite melts in the source of sanukitoids","authors":"L.M. Spencer ,&nbsp;C. Albert ,&nbsp;H.M. Williams ,&nbsp;O. Nebel ,&nbsp;I.J. Parkinson ,&nbsp;R.H. Smithies ,&nbsp;H. Bruno ,&nbsp;M. Fowler ,&nbsp;H. Moreira ,&nbsp;C.J. Lissenberg ,&nbsp;M.-A. Millet","doi":"10.1016/j.epsl.2024.119067","DOIUrl":"10.1016/j.epsl.2024.119067","url":null,"abstract":"<div><div>Sanukitoids are unique Archean and early Proterozoic igneous rocks. They contain high amounts of Mg, Ni and Cr, showing they are mantle-derived melts, while they are also enriched in Sr and Ba and have relatively high K contents, requiring the involvement of an incompatible element-enriched component likely derived from recycled crustal material. The appearance of sanukitoids in the geological record coincides with a shift in continental crust composition, and both events have been linked to a change in geodynamic processes on Earth. However, uncertainties remain about sanukitoid petrogenesis, in particular whether their mantle source was metasomatised by a metabasite-derived silicate melt or by an aqueous fluid. Titanium (Ti) stable isotopes can trace magmatic processes where silicate melts are in equilibrium with Fe-Ti oxides and amphibole but are insensitive to fluid-driven processes, making them a suitable tool to investigate not only the formation of sanukitoid magmas but also their subsequent evolution. Here we present Ti isotope data (δ⁴⁹Ti) for a series of Neoarchean sanukitoids from the Yilgarn Craton that continuously covers the full compositional range of sanukitoids. These are complemented by Mesoarchean sanukitoids and Paleoarchean “sanukitoid-like” rocks from the Pilbara Craton, and by Paleoproterozoic sanukitoids from the São Francisco Craton/Paleocontinent. In addition, we analysed Paleozoic high Ba-Sr granite suites from Scotland, which are proposed to be Phanerozoic sanukitoid analogues.</div><div>Evolved sanukitoids, which formed after Fe-Ti oxide saturation, show a more muted δ⁴⁹Ti increase during differentiation compared to currently analysed modern calc-alkaline suites. This difference is best explained by removal of significant proportions of Ti during sanukitoid differentiation by magmatic hornblende, which fractionates Ti isotopes less strongly than Fe-Ti oxides. Combined with early oxide saturation at high Mg#, this suggests that sanukitoid parental magmas had H₂O contents and fO₂ at least as high as modern arc magmas. Primitive (pre-oxide saturation) sanukitoids, however, have significantly higher δ⁴⁹Ti (0.11–0.20‰) than modern arc basalts, the depleted mantle and the bulk silicate Earth (BSE). Their elevated δ⁴⁹Ti values cannot be explained by aqueous fluids alone in their mantle source, and instead require the involvement of a hydrous eclogite melt component formed in equilibrium with residual rutile. We favour generation of this metasomatic melt by fluid-fluxed eclogite partial melting, demonstrating that both metabasite melts and aqueous fluids are important for sanukitoid formation. The Ti isotope compositions of Archean and Paleoproterozoic sanukitoids therefore favour formation of the sanukitoid mantle source by a subduction-like process at least ∼2.7 Ga.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119067"},"PeriodicalIF":4.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The viscosity of a partially molten layer in a paleo-orogenic plateau","authors":"Z. Molitor ,&nbsp;T. Mittal ,&nbsp;O. Jagoutz","doi":"10.1016/j.epsl.2024.119060","DOIUrl":"10.1016/j.epsl.2024.119060","url":null,"abstract":"<div><div>Orogenic plateaus (e.g., Tibet, Altiplano) are characterized by broad, flat-top topography at high elevation and significantly increased crustal thickness. Partial melt is thought to weaken the middle crust of orogenic plateaus, and thus reduce the viscosity of the crust; however, the amount of partial melt and the magnitude of associated weakening remain unconstrained. The New England Appalachians represent an exposed mid- to lower crustal section of a paleo-orogenic plateau, similar to modern-day Tibet. In this study, we utilize the relationship between the spacing of deformation bands and the compaction length to constrain mid-crustal shear viscosity in a late Devonian migmatite. We find that the viscosity of the middle orogenic crust in the paleo-orogenic plateau of the New England Appalachians is 10^17–18 Pa∙s at ∼3–9% melt. This finding is consistent with geophysical models of orogenic channel flow and provides field-based evidence for a significant rheologic transition at low melt-fraction. Our results suggest that the key elements for the formation of a weak, mid-crustal layer in orogenic plateaus are an influx of water and temperatures near the hydrous granite solidus.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119060"},"PeriodicalIF":4.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441204","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":"Detection of a ULVZ in the Central Pacific using high frequency Sdiff postcursors","authors":"Carl Martin ,&nbsp;Stuart Russell ,&nbsp;Sanne Cottaar","doi":"10.1016/j.epsl.2024.119028","DOIUrl":"10.1016/j.epsl.2024.119028","url":null,"abstract":"<div><div>In recent decades, ultra-low velocity zones (ULVZs) – thin patches of strongly reduced seismic velocity atop the core-mantle boundary (CMB) – have been inferred from observations of a variety of seismic phases. One such phase is Sdiff and its out-of-plane postcursory energy, Sdiff+. In this study, we present a high quality dataset of Sdiff and Sdiff+ which shows evidence of a ULVZ in the central Pacific, roughly between Hawaii and Marquesas. The observed Sdiff+ have an unusually short dominant period (5–12 seconds) compared to previous Sdiff+ observations, which is indicative of a ULVZ that is approximately 10–15 km thick. We analyse this high frequency dataset using the 2D Wavefront Tracker (2DWT) Bayesian inversion methodology to generate a probabilistic ensemble of ULVZ models. As a result of the uniazimuthal coverage of data, there is a strong southwest-northeast trade-off, but there is a slight preference for the ULVZ to be located just outside the Pacific large low velocity province (LLVP) boundary, roughly centred 20° north of Marquesas and 20° southeast of Hawaii. The 2DWT inversion of Sdiff+ travel times suggest that the ULVZ can be approximated as a cylindrical structure; either as a larger and weaker anomaly (radius 280 km, dVs -20%) close to the LLVP, or a smaller and stronger anomaly (radius 180 km, dVs -30%) further away from the LLVP. Unlike previous broad-scale ULVZs modelled with Sdiff+, this ULVZ is thinner, might lie outside of an LLVP, and lacks a potential relationship to a mantle plume.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"648 ","pages":"Article 119028"},"PeriodicalIF":4.8,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ring faulting and piston collapse in the mantle sustained the largest submarine eruption ever documented","authors":"E. Jacques ,&nbsp;R. Hoste-Colomer ,&nbsp;N. Feuillet ,&nbsp;A. Lemoine ,&nbsp;J. van der Woerd ,&nbsp;W.C. Crawford ,&nbsp;C. Berthod ,&nbsp;P. Bachèlery","doi":"10.1016/j.epsl.2024.119026","DOIUrl":"10.1016/j.epsl.2024.119026","url":null,"abstract":"<div><div>The basaltic submarine eruption offshore the island of Mayotte between July 2018 and January 2021 is one of the largest documented underwater eruptions. One of the most striking differences between this eruption and most documented eruptions is the exceptional depth of the associated seismicity, which is limited almost exclusively to the lithospheric mantle. This seismicity probably outlines magma reservoirs and dyking zones.</div><div>In order to better understand the deep processes driving the eruption, we analyze precise earthquake locations and focal mechanisms associated with this event. We present a set of 2677 accurate earthquake relocations and 300 focal mechanisms determined from data collected over the first 9 months of ocean bottom seismometer deployments, starting in February 2019.</div><div>Our relocations refine the structure of two swarms (Proximal and Distal with respect to Mayotte), and reveal well-defined mantle structures between 20 and 55 km below sea level, which we interpret as a ring-fault zone and a dyke, respectively. The Proximal swarm outlines a ring-fault zone as the locus of a large piston collapse caused by the deflation of an underlying magma reservoir. Deformation around the piston is driven by normal faulting on a set of inward dipping patches surrounding the piston. Locally, collapse of the conical shaped piston causes a radial extensional stress field with strike-slip and normal faulting ruptures accommodating the relaxation of the damaged zone around the piston.</div><div>This piston collapse allowed the transfer of lava to the eruption site via the dyke highlighted by the Distal earthquake swarm. The link between the swarms is thus magmatic, in agreement with petrological analyses of lava from the new volcano.</div><div>This is the first time that piston collapse and localized dyking have been documented in the mantle. The pattern of deformation documented here could apply to shallower, crustal piston collapses, such as in Iceland.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119026"},"PeriodicalIF":4.8,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lithium isotope stratigraphy and Ordovician weathering","authors":"Y. Datu Adiatma ,&nbsp;Matthew R. Saltzman ,&nbsp;Xiao-Ming Liu ,&nbsp;Xi-Kai Wang ,&nbsp;Cole T. Edwards","doi":"10.1016/j.epsl.2024.119030","DOIUrl":"10.1016/j.epsl.2024.119030","url":null,"abstract":"<div><div>Understanding the role of silicate weathering in controlling the long-term carbon cycle is essential in exploring multi-million-year scale climate variabilities and links to tectonics and changes in biodiversity. The lithium isotopic composition of carbonate rocks (δ⁷Li) is a non-traditional proxy that offers a more comprehensive understanding of silicate weathering dynamics in the geologic past in combination with traditional weathering proxies such as strontium isotopes (⁸⁷Sr/⁸⁶Sr). However, questions related to the effects of diagenesis and the relationship between changes in δ⁷Li and CO₂ consumption during silicate rock weathering hamper the use of this novel proxy to its full potential. Here we present measurements of bulk carbonate δ⁷Li that span the Ordovician Period from six sections across the Laurentian paleocontinent. Using a rigorous textural and geochemical screening, we produce the first high-resolution seawater δ⁷Li (δ⁷Li_sw) curve that spans the Tremadocian to Sandbian of the Ordovician Period (∼487 – 453 Ma). The δ⁷Li_sw curve produced in this study exhibits a ∼4‰ negative shift during the Early to Middle Ordovician. Using comparisons to existing weathering proxies and a numerical modeling approach, we suggest a progressive change toward a low-intensity, congruent weathering regime was a likely driver for the observed trend. This finding highlights potential links between island arc migration toward the tropics, global increase in exposed landmass, possible terrestrialization by non-vascular land plants and changes in silicate weathering.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119030"},"PeriodicalIF":4.8,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419374","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":"Rhenium isotope variations in Icelandic groundwaters and hydrothermal systems","authors":"Wenhao Wang ,&nbsp;Alexander J. Dickson ,&nbsp;Mathieu Dellinger ,&nbsp;Kevin W. Burton ,&nbsp;Deirdre E. Clark ,&nbsp;Guðjón Helgi Eggertsson ,&nbsp;Íris Eva Einarsdóttir ,&nbsp;Heimir Ingimarsson ,&nbsp;Kiflom Gebrehiwot Mesfin ,&nbsp;Robert G. Hilton ,&nbsp;Julie Prytulak","doi":"10.1016/j.epsl.2024.119046","DOIUrl":"10.1016/j.epsl.2024.119046","url":null,"abstract":"<div><div>The isotopic composition of rhenium (Re) has potential for use as a proxy to infer changes in seafloor redox and/or global oxidative weathering intensity. Despite an emerging dataset on this nascent isotope system in Earth's surficial environments, very little is known about processes that control Re isotope fractionation, nor the isotopic composition of hydrothermal systems. Here we present Re concentrations and Re isotopic compositions (reported as δ¹⁸⁷Re, relative to NIST 3143) of groundwaters and hydrothermal fluids from three Icelandic settings. First, we show that high-temperature fluids that have experienced vapour-phase segregation (boiling) from the Reykjanes peninsula and the Hengill volcanic system have the highest δ¹⁸⁷Re values (−0.01 to +0.34 ‰) observed to date, inferred to result from Re isotope fractionation during incorporation of Re into secondary reduced minerals. Second, we examine the Mývatn area in northern Iceland, which has both cold and warm groundwaters. Cold groundwaters (&lt; 10 °C) have δ¹⁸⁷Re values indistinguishable from Icelandic basalts (−0.36 to −0.32 ‰) whilst warm waters have higher δ¹⁸⁷Re (−0.31 to +0.19 ‰) which increase with increasing temperature (up to 45 °C). The variation of δ¹⁸⁷Re in Mývatn groundwaters is closely mirrored by variations in δ⁹⁸Mo, consistent with mixing between compositionally distinct water end-members. Finally, geothermal waters from the Geysir field have variable Re concentrations and δ¹⁸⁷Re values (−0.23 to +0.34 ‰), likely reflecting multiple physico-chemical processes. Using these results, we show that hydrothermal activity is unlikely to exert a large net impact on the seawater Re budget, nor the secular changes in seawater δ¹⁸⁷Re. These findings also point toward developing a novel Re isotope tracer for redox processes.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119046"},"PeriodicalIF":4.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inferring relative sediment fluxes and landscape evolution trends from C, O and clumped isotopes and mineral composition in detrital carbonate","authors":"Ravid Hagbi ,&nbsp;Liran Goren ,&nbsp;John M. Eiler ,&nbsp;Uri Ryb","doi":"10.1016/j.epsl.2024.119031","DOIUrl":"10.1016/j.epsl.2024.119031","url":null,"abstract":"<div><div>The Earth's surface undergoes continuous changes due to the redistribution of surface mass through erosion, sediment transport, and deposition. Quantifying these mass fluxes is essential for understanding the patterns and rates of landscape evolution. Established approaches for estimating these fluxes in drainage basins often fail to distinguish among bedrock sources and suffer from transport-related biases. This problem is emphasized in carbonate terrains that typically lack distinct mineral compositions indicative of sediment sources.</div><div>Here, we develop a novel approach that combines established mineral proxies, together with oxygen, carbon and ‘clumped’ isotope analyses of detrital carbonates, to evaluate the provenance and relative fluxes of sediment in carbonate-dominated drainage systems. The new approach is applied to the Morag catchment in the Hatrurim Syncline, southern Israel, a well-suited and illustrative field case for its large variability in isotope compositions between marine and metamorphosed carbonate rock sources. In this setting, the clumped isotope analysis is a sensitive tool, enabling us to distinguish among potential source units by their thermal history.</div><div>The analysis reveals that the variations in mineral and isotope compositions of sediment samples collected from various locations in the Morag catchment are consistent with mixing between two end-member carbonate bedrock sources. We developed an inverse mixing model that infers the compositions of these sources and predicts the mixing-ratio based on the measured mineral and isotope compositions from sediment samples. Optimal sources found by the model are consistent with: 1) Marine carbonates; and 2) marine carbonates altered by post-metamorphic re-crystallization.</div><div>Model-predicted mixing ratios of end member components of the sediment samples correlate with relative exposure areas of relevant source units. This consistency suggests spatially uniform erosion conditions, such that relief is neither created nor destroyed within at least one fluvial response time. Consequently, a prominent increase in steepness across a lithologic and structural boundary at the upper reaches of the catchment is interpreted to reflect a signature of lithology-dependent erodibility, rather than faster erosion of the steeper terrain.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119031"},"PeriodicalIF":4.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142420036","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":"Abiotic origin of organics in the martian regolith","authors":"Arthur Goodwin ,&nbsp;Christian Schröder ,&nbsp;Emily Bonsall ,&nbsp;Russell J. Garwood ,&nbsp;Romain Tartèse","doi":"10.1016/j.epsl.2024.119055","DOIUrl":"10.1016/j.epsl.2024.119055","url":null,"abstract":"<div><div>The martian meteorite Northwest Africa (NWA) 11220 and paired stones (notably NWA 7034) are the only group of meteorites that sample a clastic near-surface lithology from Mars. The stones have been recognized as an impact-reworked lithology subjected to an impact-induced hydrothermal system — comparable to the postulated history of Jezero Crater, currently being explored by the NASA Perseverance rover. By applying Mössbauer spectroscopy in combination with several in situ analytical techniques including Raman spectroscopy, FTIR spectroscopy, and NanoSIMS, we show that aliphatic carbon compounds dominate the inventory of insoluble indigenous carbon compounds within NWA 11220. Disordered carbon — present in ∼5 μm heterogeneous masses — is preferentially found within porosity where it adjoins the mineral surface of titano-magnetite. This relationship suggests catalytic surfaces have enabled Fischer–Tropsch (FT) synthesis of hydrocarbons. Our in situ micron-scale analytical study indicates that such methods can help determine the origin of organic material that exists in the near-surface martian regolith. Such multimodal approaches will be a key methodology for searching for traces of past life in future samples returned from Mars.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119055"},"PeriodicalIF":4.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Postseismic deformation due to the 2021 MW 7.4 Maduo (China) earthquake and implications for regional rheology and seismic hazards around the Bayan Har block","authors":"Zhen Tian ,&nbsp;Jeffrey T. Freymueller ,&nbsp;Yang He ,&nbsp;Guofeng Ji ,&nbsp;Shidi Wang ,&nbsp;Zhenhong Li","doi":"10.1016/j.epsl.2024.119059","DOIUrl":"10.1016/j.epsl.2024.119059","url":null,"abstract":"<div><div>GPS and InSAR observations of the first ∼1.5 years of postseismic deformation caused by the 2021 <em>M_W</em> 7.4 Maduo earthquake provide a valuable opportunity to investigate fault interactions and regional rheological structure, as well as the future seismic potential around the Bayan Har block, northeastern Tibetan Plateau. We develop an integrated model to simulate the afterslip and viscoelastic relaxation contributions to the observed postseismic displacements, and found that afterslip driven by the coseismic stress is concentrated downdip of rupture, and dominates the postseismic deformation in the early stage (∼0.4 year after the event). Because afterslip decays quickly over time, viscoelastic relaxation should become the main postseismic mechanism as time goes on. The two mechanisms produce similar displacements during 0.4–1.5 years after the earthquake, but at 1.5 years after the earthquake the velocity caused by viscoelastic relaxation is larger than that caused by afterslip. Viscoelastic models assuming either a Burgers body or power-law rheology produce very similar predictions, with the Burgers body model having a slightly lower overall misfit. The rheological structure constrained by the postseismic observations supports the 35-km thick elastic upper crust overlying a Burgers body viscoelastic lower curst with a Maxwell viscosity of 3 × 10¹⁹ Pa s (5 - 50 × 10¹⁸ Pa s at 95% confidence), assuming the Kelvin viscosity is equal to 10% of that value. This is different from the regional rheology inferred by the postseismic investigations on the 2001 <em>M_W</em> 7.8 Kokoxili and the 2008 <em>M_W</em> 7.8 Wenchuan events, and the preferred thickness of the elastic crust is also different from that inferred from magnetotelluric profiles deployed in previous studies. We thus infer that the rheological structure within the Bayan Har block is possibly heterogeneous from west to east. Finally, the normal stress changes triggered by the coseismic rupture and postseismic process are estimated to be negative, but the shear stress changes to be positive on the western Kunlun fault, the eastern Dari fault and Bayan-Har Mountain fault. However, the current observations and studies are quite insufficient on those fault segments, therefore, we need to focus on their faulting behavior and seismic risk in the future.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"647 ","pages":"Article 119059"},"PeriodicalIF":4.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419372","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}