Abstract The Trans-European Suture Zone (TESZ) is the most important and extensive continental suture in Europe, marking the edge of the East European Craton (EEC), from the North Sea to the Black Sea. It corresponds to significant changes in surface geology and deep crustal structure, evident in seismic, gravitational and magnetic studies. However, the TESZ disappears beneath the Eastern Carpathians accretionary nappes and Neotethys ophiolites, thrusted over the subducted EEC passive margin in Romania that may have experienced progressive southward break-off generating post-collisional volcanism and anomalous seismicity in the Vrancea region of the South-East Carpathians To illuminate the missing TESZ section and investigate the change in crustal properties from the Precambrian EEC across the collisional orogen and the impact of related volcanism, we determined a 3D seismic model of P and S wave velocities of the Eastern Carpathians in Romania. With the advent of new permanent broadband and short-period seismic stations of the Romanian Seismic Network, we were able to lower the earthquake magnitude detection threshold to 0.5 ML, largely expanding the earthquake database, and create seismic images of the crust across the Carpathians. Using double-difference tomography and waveform cross-correlation differential times, we relocated local crustal earthquakes between 2010 and 2017 and jointly inverted for the 3D P and S -wave velocity structure down to the Moho discontinuity. Our study provides the highest resolution 3D crustal seismic model of this area to date and emphasizes the manifestation of surface tectonic boundaries at lower crustal depths. The TESZ is highlighted at mid-to lower-crustal depths beneath the Carpathian nappes, east of the post-collisional volcanic belt, as a gently-dipping transition from high Vp in the eastern footwall, the dipping Precambrian basement, to low Vp beneath the Carpathian Orogen to the west and a downward decrease in Vp/Vs. In parts of the volcanic region, Vp/Vs ratios increase suggesting the presence of fluids, mafic material and partial melts that may have altered the seismic structure of the TESZ. Relocated hypocenters are vertically distributed in the velocity transition zone from low to high especially beneath the youngest volcanoes in the south, consistent with a hypothetically active magmatic plumbing system. In the northern segment, where volcanoes are older, relatively high velocities are estimated and seismicity tends to cluster in the top 10 km, likely connected to a recently reactivated fault system. Seismicity in the foreland of the East Carpathians aligns along the NW-SE trending major crustal faults and continues beneath the thrust belt, suggesting the East European Craton basement extends beneath the orogen as far as the volcanic belt.

中文翻译：

---

缺失的克拉通边缘：双差断层扫描揭示喀尔巴阡造山带下东欧克拉通的地壳结构

摘要 跨欧缝合带（TESZ）是欧洲最重要、最广泛的大陆缝合带，标志着东欧克拉通（EEC）从北海到黑海的边缘。它对应于地表地质和深部地壳结构的显着变化，在地震、重力和磁学研究中很明显。然而，TESZ 消失在东喀尔巴阡山增生推覆和新特提斯蛇绿岩之下，推覆在罗马尼亚俯冲的 EEC 被动边缘，该边缘可能经历了逐渐向南的断裂，在东南部的 Vrancea 地区产生了碰撞后火山作用和异常地震活动喀尔巴阡山脉为了阐明缺失的 TESZ 部分并研究前寒武纪 EEC 穿过碰撞造山带的地壳性质的变化以及相关火山作用的影响，我们确定了罗马尼亚东喀尔巴阡山脉 P 波和 S 波速度的 3D 地震模型。随着罗马尼亚地震台网新的永久性宽带和短周期地震台站的出现，我们能够将地震震级检测阈值降低到 0.5 ML，大大扩展了地震数据库，并创建了喀尔巴阡山脉地壳的地震图像。使用双差断层扫描和波形互相关微分时间，我们重新定位了 2010 年和 2017 年之间的局部地壳地震，并联合反演了 3D P 和 S 波速度结构到莫霍面不连续性。我们的研究提供了该地区迄今为止最高分辨率的 3D 地壳地震模型，并强调了地壳下部深度地表构造边界的表现。TESZ 突出显示在碰撞后火山带以东的喀尔巴阡推覆岩之下的中下地壳深度，从东部下盘的高 Vp 和倾斜的前寒武纪基底到低 Vp 的缓倾过渡喀尔巴阡造山带向西，Vp/Vs 下降。在部分火山区，Vp/Vs 比值增加表明流体、基性材料和部分熔体的存在可能改变了 TESZ 的地震结构。重新定位的震源垂直分布在从低到高的速度过渡带，特别是在南部最年轻的火山下方，与假设活跃的岩浆管道系统一致。在火山更古老的北段，估计速度相对较高，地震活动往往集中在前 10 公里，可能与最近重新激活的断层系统有关。东喀尔巴阡山脉前陆的地震活动沿着 NW-SE 走向的主要地壳断层排列，并在逆冲带下方继续，这表明东欧克拉通基底在造山带下方一直延伸到火山带。