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Exhumation history of the eastern Tethyan Himalaya: Evidence from Apatite (UTh)/He Thermochronology 特提斯喜马拉雅东部的发掘史：来自磷灰石(U - Th)/He热年代学的证据

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-12-05 DOI: 10.1016/j.tecto.2025.231035

Xu Han, Jin-Gen Dai, Bo-Rong Liu, Zhi-Cheng Yu

The Himalayan orogen is an ideal natural laboratory for investigating exhumation processes due to the diverse and distinctive tectonic and climatic features. Whereas numerous low-temperature thermochronometric studies have been conducted on southern flank of the orogen (mainly in the Greater Himalaya and Lesser Himalaya), the dominant controls on exhumation remain debated due to the complex interactions between climate, topography, and tectonics. In contrast, the Tethyan Himalaya along the northern flank exhibits relatively limited recent tectonic activity and spatially uniform precipitation, which makes it more suitable for exploring controlling factors of exhumation. To reconstruct the exhumation history of the eastern Tethyan Himalaya and identify its controls, we collected bedrock samples along river channels for apatite (UTh)/He dating. Low-temperature thermochronology and thermal history modeling indicate three rapid exhumation phases: ca. 10–7 Ma, ca. 6–3 Ma, and ca. 2–0 Ma. The ca. 10–7 Ma phase correlates with the Asian summer monsoon intensification, during which increased precipitation enhanced fluvial incision. The ca. 6–3 Ma phase is the last vestige of tectonically controlled rapid exhumation in Himalaya, subsequent to the decline of the India-Asia convergence rate at ca. 6 Ma. The most recent phase (<2 Ma) is primarily linked to localized normal faulting. Additionally, a pronounced geomorphic contrast is observed: river valleys south of the Himalayan drainage divide exhibit significantly wider widths compared to tributaries of the upper and lower Yarlung River located north of the divide. These differences correlate with exhumation timing, as areas experiencing older exhumation phases exhibit wider valleys. This correlation suggests that fluvial erosion exerts a long-term control on exhumation patterns within the orogen.

喜马拉雅造山带由于其多样而独特的构造和气候特征，是研究挖掘过程的理想天然实验室。尽管在造山带南侧（主要在大喜马拉雅和小喜马拉雅）进行了大量的低温热时学研究，但由于气候、地形和构造之间复杂的相互作用，对挖掘的主要控制因素仍存在争议。而北翼特提斯喜马拉雅地区近期构造活动相对有限，降水空间均匀，更适合发掘发掘的控制因素。为了重建特提斯-喜马拉雅东部地区的挖掘历史并确定其控制因素，我们沿河道收集了基岩样品进行磷灰石(UTh)/He定年。低温热年代学和热历史模拟显示了三个快速挖掘阶段：约10-7 Ma，约6-3 Ma和约2-0 Ma。约10 ~ 7 Ma期与亚洲夏季风增强有关，降水增加使河流切口增强。约6 - 3 Ma阶段是喜马拉雅地区构造控制的快速发掘的最后遗迹，是在约6 Ma印度-亚洲辐合速率下降之后。最近的阶段（2 Ma）主要与局部正断层有关。此外，我们还观察到一个明显的地貌对比：喜马拉雅分水岭以南的河谷比位于分水岭以北的雅鲁藏布江上下游的支流明显更宽。这些差异与挖掘时间有关，因为经历较早挖掘阶段的地区显示出较宽的山谷。这种相关性表明，河流侵蚀对造山带内的挖掘模式起着长期的控制作用。

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引用次数: 0

Sensitivity analysis of lithospheric convergence velocity in numerical simulations of self-sustained Andean-type subduction 自持续安第斯型俯冲数值模拟中岩石圈辐合速度的敏感性分析

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-12-05 DOI: 10.1016/j.tecto.2025.231030

Jamison Assunção , Boris J.P. Kaus , Andrea Piccolo , Nicolas Riel , Victor Sacek

Plate velocities on Earth are all on the order of several centimeters per year, despite large uncertainties in mantle rheology and plate geometry. Here, we conducted a series of 2D self-sustained Andean-type subduction simulations, and investigated how the convergence speed between an oceanic and a continental lithosphere is influenced by plate geometry, lower mantle rheology and the presence of a partial melt zone (PMZ) of relatively low viscosity under the oceanic lithosphere. We ran sets of simulations with different oceanic plate lengths at the surface (OPLS), ranging from 1000 to 5000 km. The overall subduction pattern displayed a relatively rapid acceleration of the subducting plate, followed by a deceleration of approximately the same duration until the plate reached the lower mantle. After this point, the convergence velocity tends to remain stable, varying up to 3.5 cm/yr during subduction across most of the simulated scenarios, supporting the hypothesis of sustained convergence rates for tens of millions of years. We found a linear relationship between the OPLS and the average convergence speed after the plates reach the 660-km discontinuity, with the average convergence velocity decreasing by a rate of approximately 1.3 cm/yr per each additional 1000 km of OPLS. We also tested the sensitivity of the average convergence velocity to variations in lower mantle viscosity and found that decreasing the viscosity from 1.5 × 10²² to 0.5 × 10²² Pa s increased the convergence speed of the subducting plate – after reaching the 660-km discontinuity – by up to a factor of three, hindering convergence stability. By testing the effect of a PMZ modeled via asthenospheric rheology scaling, we found that it does not significantly alter the convergence speed stability or affect the kinematics. Instead, it primarily mimics the behavior of a scenario with a smaller oceanic plate.

地球上的板块速度都在每年几厘米左右，尽管地幔流变学和板块几何结构存在很大的不确定性。在此，我们进行了一系列二维自持续安第斯型俯冲模拟，并研究了板块几何形状、下地幔流变学以及海洋岩石圈下相对低粘度的部分熔融带（PMZ）的存在如何影响海洋和大陆岩石圈之间的收敛速度。我们用不同的海洋表面板块长度（ops）进行了一组模拟，范围从1000到5000公里。整个俯冲模式表现为俯冲板块的相对快速加速，随后是一个大约相同时间的减速，直到板块到达下地幔。在此之后，收敛速度趋于稳定，在大多数模拟情景中，在俯冲期间变化高达3.5 cm/年，支持持续数千万年的收敛速度假设。在到达660 km不连续面后，ops与平均辐合速度呈线性关系，每增加1000 km ops，平均辐合速度降低约1.3 cm/yr。我们还测试了平均辐合速度对下地幔黏度变化的敏感性，发现黏度从1.5 × 1022 Pa s降低到0.5 × 1022 Pa s会使俯冲板块的辐合速度（在达到660公里的不连续面后）增加三倍，从而阻碍了辐合的稳定性。通过测试软流圈流变缩放模型对PMZ的影响，我们发现它不会显著改变收敛速度、稳定性或影响运动学。相反，它主要是模仿一个较小的海洋板块的行为。

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引用次数: 0

The aggregation-diffusion effect of shallow motions in the 2022 Menyuan Mw 6.6 earthquake 2022年门源Mw 6.6地震浅层运动的聚集-扩散效应

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-12-02 DOI: 10.1016/j.tecto.2025.231033

Anhua Ju , Haiqing Yang , Xingyue Li , Lixin Peng

The dynamic processes of the Earth's surface before and after an earthquake have long been central to seismological research. However, the relationship between surface motions and seismic activity remains difficult to establish. This study proposes a novel method for quantifying the orderliness of surface motions. The method defines trend direction at each time step based on the three-dimensional displacement time series derived from Sentinel-1 SAR images from different orbits. It also describes the aggregation and diffusion effects of motion directions before and after the earthquake. Additionally, a horizontal displacement acceleration-deceleration detection model based on piecewise linear fitting identifies monthly acceleration and deceleration points throughout the seismic event. The results showed that the observable horizontal displacement was significantly larger than the vertical displacement, exhibiting the strike-slip faulting characteristics of the 2022 Mw 6.6 Menyuan earthquake. The average information entropy was 6.088 before the earthquake, dropped to 5.943 near the event, and rose to 6.067 afterward. Surface motion direction and amplitude exhibit a process of aggregation and acceleration followed by diffusion and deceleration. This indicates that geodetic techniques can detect subtle surface motion changes potentially linked to seismic preparation processes.

地震前后地球表面的动态过程一直是地震学研究的核心。然而，地表运动和地震活动之间的关系仍然难以确定。本研究提出了一种量化地表运动有序性的新方法。该方法基于Sentinel-1不同轨道SAR图像的三维位移时间序列，定义每个时间步长的趋势方向。还描述了地震前后运动方向的聚集和扩散效应。此外，基于分段线性拟合的水平位移加减速检测模型可以识别整个地震事件中每个月的加速度和减速点。结果表明，观测到的水平位移明显大于垂直位移，表现出2022年门源Mw 6.6地震的走滑断裂特征。平均信息熵在震前为6.088，震前降至5.943，震后上升至6.067。地表运动方向和振幅表现为聚集-加速-扩散-减速的过程。这表明大地测量技术可以探测到可能与地震准备过程有关的细微地表运动变化。

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引用次数: 0

Control of crustal melt migration on geothermal system development in the Daggyai area, southern Tibet: Insights from 3D magnetotelluric imaging

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-12-01 DOI: 10.1016/j.tecto.2025.231032

Menglong Liao , Yuanzhi Cheng , Bo Han , Zhonghe Pang

The Daggyai geothermal field in the southern Tibetan Plateau is characterized by abundant boiling springs and geysers, with thermal waters exhibiting significant enrichment in trace elements (As, B, and Li). To investigate the formation mechanisms and geothermal potential of this hydrothermal system, we conducted a magnetotelluric (MT) survey along a north–south profile across the field and developed a 3D resistivity model using ModEM. Integration of resistivity modeling, geochemical data, and geological observations reveals the following characteristics: (1) A shallow low-resistivity body functioning as the primary geothermal reservoir; (2) A low-resistivity body at intermediate depths (4–10 km) indicating either a fluid-dominated high-temperature rock mass or a zone containing a high aqueous phase with limited partial melt; (3) A pronounced low-resistivity body at depths of 10–18 km representing the principal heat source, interpreted as a partially molten rock body with melt fractions of 5.72–11.15%; (4) An additional deep low-resistivity body providing evidence of significant crustal melting, with estimated melt fractions of 8.13–14.61%. The resistivity structure demonstrates clear electrical connectivity between the deep crustal melting zone and the principal heat source region. We propose that the ongoing India–Eurasia continental collision facilitates the upward migration of crustal melts, which subsequently accumulate beneath the Daggyai field, sustaining its high-temperature hydrothermal system. This mechanism suggests that other high-temperature geothermal systems in southern Tibet characterized by shallow partial melt heat sources may share similar patterns of melt migration and accumulation, providing crucial insights into the evolution of geothermal systems across the southern Tibetan Plateau.

为了研究该热液系统的形成机制和地热潜力，我们沿南北剖面进行了大地电磁测量，并利用ModEM建立了三维电阻率模型。电阻率模拟、地球化学资料和地质观测相结合，揭示出以下特征：(1)浅层低电阻率体为主力地热储层；(2)中深度（4 ~ 10 km）低电阻率体，表明以流体为主的高温岩体或含部分熔体有限的高水相带；(3) 10 ~ 18 km深处有明显的低电阻率体，为主要热源，为部分熔融岩体，熔体分数为5.72 ~ 11.15%；(4)另一个深部低电阻率体提供了地壳明显熔融的证据，估计熔融分数为8.13 ~ 14.61%。电阻率结构显示了深部地壳熔融带与主热源区之间明显的电性连通性。我们认为，持续的印度-欧亚大陆碰撞促进了地壳熔体的向上迁移，这些熔体随后积聚在大盖野下，维持了大盖野的高温热液系统。

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引用次数: 0

Complex seismic anisotropy beneath the North China Craton from long-term shear wave splitting analysis 华北克拉通地下复杂地震各向异性的长期横波分裂分析

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-30 DOI: 10.1016/j.tecto.2025.231031

Wen Meng , Yonghua Li , Xiaoyu Yang

We investigate a contrast in the anisotropic complexity beneath different blocks of the North China Craton (NCC) using shear wave splitting measurements from teleseismic SKS, SKKS, and PKS phases recorded at 113 permanent stations over fifteen years. The systematic variations of splitting parameters with back azimuth observed at stations across various blocks have been modeled using two-layers anisotropic structure. The observed ENE-WSW-oriented fast polarization direction (FPD) in the upper layer beneath the Ordos Block is interpreted as frozen-in lithospheric anisotropy, likely inherited during cratonic formation. The FPD of the upper layer across the Circum-Ordos Rifts is consistent with the rift strike, which may be the result of a combined effect of pre-rift orogenic-related lithospheric fabric, oriented melt pockets or/and simple shear deformation associated with the counterclockwise rotation of the Ordos Block. The FPD in the upper layer beneath the Taihang Orogenic Belt is consistent with the strike of the orogenic belt, suggesting a possible association with past lithospheric orogenic deformation. In the lower layers of all regions modeled with two-layers anisotropic structure, FPDs are consistent with the direction of absolute plate motion (APM), reflecting the flow in the asthenosphere. However, in regions where the lithospheric thickness changes rapidly, such as along the margins of the Ordos Block and around the Datong Volcanic area, there are significant directional deviations between FPDs and APM. This suggests that lithospheric heterogeneity and upwelling mantle flow have a significant modulating effect on the asthenospheric flow.

本文利用华北克拉通（NCC） 113个永久台站近15年的远震SKS、SKKS和PKS相横波分裂测量数据，研究了华北克拉通不同地块各向异性复杂性的对比。利用两层各向异性结构，模拟了各测点观测到的分裂参数随反方位角的系统变化。鄂尔多斯地块下上层观测到的ene - wsw定向快速极化方向（FPD）解释为冻结岩石圈各向异性，可能是在克拉通形成时期继承的。环鄂尔多斯断陷上部的FPD与裂谷走向一致，这可能是与裂陷前造山作用相关的岩石圈结构、定向融袋或与鄂尔多斯地块逆时针旋转相关的单纯剪切变形共同作用的结果。太行造山带下上层FPD与造山带走向一致，可能与过去岩石圈造山变形有关。在所有采用两层各向异性结构模拟的区域的低层，FPDs与绝对板块运动（APM）方向一致，反映了软流层的流动。然而，在岩石圈厚度变化较快的地区，如鄂尔多斯地块边缘和大同火山区周围，FPDs和APM之间存在明显的方向性偏差。这表明岩石圈非均质性和地幔上升流对软流圈流动具有显著的调节作用。

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引用次数: 0

Escape tectonics 逃避构造

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-28 DOI: 10.1016/j.tecto.2025.231029

Donna L. Whitney , Maximiliano Bezada , Lars N. Hansen , Christian Teyssier , Ikuko Wada , Xin Zhou

Tectonic escape is the movement of large, strike-slip fault-bounded blocks of lithosphere obliquely away from collision zones. The process of escape has occurred in its current form since the inception of plate tectonics and likely operated as ‘soft escape’ in the hotter, early Earth.

Escape is driven by collision of a smaller, stronger continent or terrane with a larger, weaker continent. The collider acts as an indenter following consumption of oceanic lithosphere at its leading edge, when collision commences between the indenter and the larger, overriding plate. Owing to heterogeneities in the strength of the escape system and the dynamics of neighboring regions, escape occurs in a preferred direction: escaping lithosphere moves as a wedge-shaped block away from rheologically strong domains and towards weaker, thinner, and/or extending domains.

Insights from active escape systems and thermo-mechanical models indicate that pre- to syn-collision factors that drive or facilitate escape likely include (1) the presence or development of localized weak zones in the overriding plate and along the indenter-ocean boundary, and (2) the continuation of a driving force for escape following slab break-off downdip of the indenter. In large-scale active escape systems, the bounding strike-slip fault closest to the collisional plate boundary is more seismically active than the escape fault further from the collision zone.

Escape has been a significant contributor to heat and mass transfer over geological time, and it affects the lithosphere from mantle to surface. It is a mechanism for the formation of new plates from existing ones and has had a major role in the tectonic history of the planet; e.g., during supercontinent assembly and dispersal. Although escape involves profound strain localization along the bounding seismically-active strike-slip faults, the effects of the escape system encompass processes within and beyond the escaping block or plate.

构造逃逸是大型的走滑断界岩石圈块体斜向远离碰撞带的运动。自板块构造开始以来，这种逃逸过程就以目前的形式发生了，并且可能在较热的早期地球上以“软逃逸”的方式运作。逃逸是由一个更小、更强的大陆或地形与一个更大、更弱的大陆碰撞造成的。当压痕与较大的覆盖板块之间开始碰撞时，在其前缘海洋岩石圈的消耗之后，碰撞器充当压痕。由于逃逸系统的强度和邻近区域的动力学的非均质性，逃逸发生在一个优先的方向：逃逸岩石圈作为一个楔形块体从流变学强的区域向较弱、较薄和/或延伸的区域移动。主动逃逸系统和热力学模型表明，驱动或促进逃逸的碰撞前后因素可能包括：(1)上覆板块和压头-海洋边界上局部弱带的存在或发育，以及(2)压头板块断裂下倾后逃逸驱动力的延续。在大型活动逸出系统中，最靠近碰撞板块边界的边界走滑断层比远离碰撞带的逸出断层更具有地震活动性。在地质时期，逸出一直是热量和质量传递的重要贡献者，它影响着从地幔到地表的岩石圈。它是现有板块形成新板块的机制，在地球的构造史上起着重要作用；例如，在超大陆组合和分散期间。虽然泄漏涉及沿边界地震活动走滑断层的深刻应变局部化，但泄漏系统的影响包括泄漏块体或板块内部和外部的过程。

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引用次数: 0

Corrigendum to ‘Virtual earthquakes in a numerical granular rock box experiment’ [Tectonophysics Volume 874 (2024) 230230] “数值颗粒岩石箱实验中的虚拟地震”的勘误表[构造物理学卷874 (2024)230230]

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-28 DOI: 10.1016/j.tecto.2025.231010

Mikito Furuichi , Jian Chen , Daisuke Nishiura , Ryuta Arai , Yuzuru Yamamoto , Satoshi Ide

引用次数: 0

Seismogenic and rheological behaviours from time-dependent analysis of earthquake depth distribution in the Corinth Rift 科林斯裂谷地震深度分布时变分析的发震和流变特征

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-27 DOI: 10.1016/j.tecto.2025.231008

A. Septier , J. Déverchère , J. Perrot , A. Renouard

Understanding earthquake depth distribution is critical for improving seismogenesis models. While the spatiotemporal pattern of earthquakes is well studied, transient changes in depth distribution remain poorly explored. In this study, we investigate how crustal rheological parameters influence the depth of earthquakes through time, focusing on the Corinth rift, a well-monitored region experiencing a high-level seismic activity in a homogeneous extensional stress field.

To calculate crustal yield strength profiles, we compile geophysical and geological data, including heat flow, rock compositions and properties, Moho depth and strain rate. These estimates are then compared to a high-quality 11-year seismic catalogue of the region. An inversion approach is applied to identify crustal layers associated with persistent versus sporadic seismicity defined here instead of the conventional background versus clustered seismicity.

Our time analysis reveals that the persistent seismicity nicely matches the theoretical brittle–ductile transition and allows us to confidently define the seismogenic thickness, while sporadic seismicity is clustered at depths associated with swarm occurrences. Both distributions are subject to kilometre-scale changes after magnitude 4.0 – 5.5 earthquakes, evidencing a relaxation process even after moderate magnitude events. We conclude that in specific case studies aiming to compare depth distribution and yield strength in the crust, the application of declustering methods may not be optimal for examining the potential rheological controls on earthquake depth distribution and their temporal variations. Instead, the analysis of persistent and sporadic seismicity defined in this study is more accurate and reliable than a declustering approach and offers new and valuable insights for this comparison.

了解地震深度分布对改进地震发生模型至关重要。虽然地震的时空格局研究得很好，但深度分布的瞬态变化仍未得到充分探讨。在这项研究中，我们研究了地壳流变参数如何随时间影响地震深度，重点关注科林斯裂谷，这是一个在均匀伸展应力场中经历高水平地震活动的良好监测区域。为了计算地壳屈服强度剖面，我们收集了地球物理和地质数据，包括热流、岩石成分和性质、莫霍深度和应变率。然后将这些估计与该地区11年的高质量地震目录进行比较。应用反演方法来识别与这里定义的持续地震活动和零星地震活动相关的地壳层，而不是传统的背景地震活动和聚集地震活动。我们的时间分析表明，持续的地震活动与理论的脆性-韧性转变很好地匹配，使我们能够自信地定义发震厚度，而零星的地震活动聚集在与群发生相关的深度。在4.0 - 5.5级地震后，这两个分布都受到公里尺度变化的影响，表明即使在中等震级事件后也存在松弛过程。我们的结论是，在旨在比较地壳深度分布和屈服强度的具体案例研究中，应用聚类方法可能不是检验地震深度分布及其时间变化的潜在流变控制的最佳方法。相反，本研究中定义的持续和零星地震活动的分析比聚类方法更准确和可靠，并为这种比较提供了新的和有价值的见解。

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引用次数: 0

Receiver function and gravity inversion of the Moho depth beneath the Baltic states 波罗的海海底莫霍深度的接收函数和重力反演

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-27 DOI: 10.1016/j.tecto.2025.231012

Viesturs Zandersons, Jānis Karušs

We present a detailed analysis of crustal thickness across the Baltic States using two geophysical methods: receiver function (RF) analysis and gravity inversion. We calculate P-wave RFs for sixteen broadband seismic stations and estimate Moho depths using both standard and sedimentary layer corrected H-k stacking. RF results show crustal thicknesses in the range from 35.5 km in northern Latvia to 55.7 km in southeastern Lithuania and northern Estonia, with corresponding

V_{p} / V_{s}

ratios between 1.70 and 1.86. These results are broadly aligned with established Proterozoic tectonic domains and prior deep seismic sounding (DSS) profiles.

Gravity inversion is performed using a terrain-corrected and spectrally filtered Bouguer anomaly field derived from WGM2012, constrained by DSS and RF-derived Moho depths. A two-layer crust-mantle tesseroid model is optimised using cross-validation and grid search. The resulting gravity-derived Moho depth varies from 44 to 49 km, with a standard deviation of 4.39 km compared to seismic estimates. Major residuals of over 10 km are observed over the Kurzeme Batholith and the West Estonian domain, highlighting the limitations of the two-layer model in regions with complex crustal architecture.

We argue for a cautious interpretation of tectonic boundaries derived solely from potential field data. Our findings support the need for a new DSS transect and integrated gravity-seismic modelling to better constrain intra-crustal structure, especially in central Latvia, southern Lithuania and northwestern Estonia where current models show significant discrepancies.

我们使用两种地球物理方法：接收函数（RF）分析和重力反演对波罗的海国家的地壳厚度进行了详细分析。我们计算了16个宽带地震台站的p波rf，并使用标准层和沉积层校正的H-k叠加来估计莫霍深度。RF结果显示，拉脱维亚北部的地壳厚度为35.5 km，立陶宛东南部和爱沙尼亚北部的地壳厚度为55.7 km，对应的Vp/Vs比值为1.70 ~ 1.86。这些结果与已建立的元古代构造域和先前的深地震测深剖面基本一致。重力反演使用WGM2012反演的地形校正和频谱滤波布格异常场，受DSS和rf反演的莫霍深度约束。利用交叉验证和网格搜索对两层壳幔曲面模型进行优化。由此得到的重力导出的莫霍深度从44到49公里不等，与地震估计值相比，标准差为4.39公里。在Kurzeme Batholith和西爱沙尼亚域观测到超过10公里的主要残差，突出了两层模型在地壳结构复杂地区的局限性。我们主张仅从位场数据推导构造边界的谨慎解释。我们的研究结果支持需要一个新的DSS样带和综合重力-地震模型来更好地约束地壳内部结构，特别是在拉脱维亚中部，立陶宛南部和爱沙尼亚西北部，目前的模型显示显着差异。

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引用次数: 0

Seismic properties of lawsonite blueschist in cold subduction zones 冷俯冲带蓝片岩的地震性质

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-25 DOI: 10.1016/j.tecto.2025.231028

Seungsoon Choi , Junha Kim , Haemyeong Jung

Anomalous seismic low-velocity layers (LVLs) have been observed at the top of subducting slabs in cold subduction zones. However, their origins remain unclear. Here, based on experimentally derived crystal preferred orientation (CPO) data of lawsonite blueschists, we demonstrate that the LVLs can be caused by the alignment of glaucophane and lawsonite. The data were obtained from general shear experiments conducted at the pressures of 1.0–2.5 GPa, temperatures of 230–400 °C, and shear strains of up to 4. The seismic velocities of deformed lawsonite blueschists were calculated based on the CPOs and elastic properties of glaucophane and lawsonite. Our results show that the average P- and S-wave velocities of deformed lawsonite blueschists are 7.69–7.85 km/s and 4.35–4.36 km/s, respectively, which are approximately 7–11 % and 10–12 % lower than surrounding mantle rocks such as peridotite and eclogite. The velocity reduction varies with the wave propagation direction and volume fraction of glaucophane and lawsonite. The P-wave velocity decreases when the wave propagates along the subduction zone strike and when the glaucophane content is high. In contrast, the S-wave velocity decreases with increasing lawsonite content, with minimal difference between the strike-parallel and along-dip propagations. These findings highlight the influence of the CPOs of minerals in deformed lawsonite blueschists on LVL formation, particularly in directional P-wave velocity variation. Since guided waves are often used to analyze subduction zone LVLs, strike-parallel ray paths may provide better constraints on low-P-wave velocity layers associated with deformed lawsonite blueschists.

在冷俯冲带俯冲板块顶部发现了异常地震低速层（LVLs）。然而，它们的起源仍不清楚。本文基于实验得出的蓝片岩晶体优先取向（CPO）数据，证明了蓝片岩的llvls可能是由蓝片岩和蓝片岩的排列引起的。数据来源于1.0 ~ 2.5 GPa压力、230 ~ 400℃温度、4 ~ 4剪切应变条件下的一般剪切实验。根据蓝闪石和蓝闪石的cpo和弹性特性，计算了变形蓝闪石的地震速度。研究结果表明，变形长粒蓝片岩的平均纵、横波速度分别为7.69 ~ 7.85 km/s和4.35 ~ 4.36 km/s，比周围的橄榄岩、榴辉岩等地幔岩石低约7 ~ 11%和10 ~ 12%。速度降低随波的传播方向和蓝透石和lawsonite的体积分数而变化。当横波沿俯冲带走向传播时，横波速度减小，且当蓝透素含量高时，横波速度减小。相反，横波速度随滑石含量的增加而减小，沿走向平行和沿倾角传播的差异很小。这些发现强调了变形lawsonite蓝片岩中矿物的CPOs对LVL形成的影响，特别是对定向纵波速度变化的影响。由于导波通常用于分析俯冲带lls，因此走向平行射线路径可以更好地约束与变形lawsonite蓝片岩相关的低纵波速度层。

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