The Pannonian region is a back-arc basin located within the arcuate Alpine–Carpathian mountain chain in central Europe. Beneath the basin both the crust and the lithosphere have smaller thickness than the continental average. During the last few decades several studies have been born to explain the formation of the Pannonian Basin but several key questions remain unanswered. In this study we construct a new high-resolution 3D P-wave velocity model of the crust and uppermost mantle in the Pannonian Basin which may help us to understand better the structure and evolution of the region. For the 3D P-wave velocity structure estimation over 32 thousand traveltime picks have been derived from the ISC bulletin and the local Hungarian National Seismological Bulletin, and altogether we used more than 3200 seismic events (local, near-regional and regional) and more than 150 seismic stations from the time period between 2004 and 2014. For the 3D velocity field inversion we used the FMTOMO software package which uses the so called Fast Marching Method for calculating the traveltime estimations, and the subspace inversion method to recover the model parameters. We also performed several checkerboard tests both to select the appropriate regularization parameters and to help the interpretation of the resulting P-wave velocity model. On the resulting tomographic image the seismic velocity anomalies well resolve the effects of deep sedimentary basins and also Moho topography and the associated updomings of the asthenosphere below the Pannonian Basin. Different major tetonic units and fault zones separating those seem to show characteristic velocity anomalies. Subrecent volcanic activity or associated melt and fluid percolation, heat transfer in the upper mantle and crust may also have an impact on the propagation of seismic waves.

中文翻译：

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使用行进时间层析成像的Pannonian盆地下方的3D P波速度图像

Pannonian地区是后弧盆地，位于中欧弧形的Alpine-Carpathian山脉内。在盆地之下，地壳和岩石圈的厚度均小于大陆平均厚度。在过去的几十年中，诞生了几项研究来解释Pannonian盆地的形成，但仍有一些关键问题尚未得到解答。在这项研究中，我们建立了Pannonian盆地地壳和最上地幔的高分辨率3D P波速度模型，这可能有助于我们更好地了解该地区的结构和演化。对于3D P波速度结构估算，已从ISC公告和当地的《匈牙利国家地震通报》中提取了32,000多个行程选择，并且我们总共使用了3200多个地震事件（本地，从2004年至2014年这段时间段内）和150多个地震台站。对于3D速度场反演，我们使用了FMTOMO软件包，该软件包使用了所谓的快速行进法来计算行进时间估计和子空间反演方法恢复模型参数。我们还执行了几项棋盘格测试，以选择合适的正则化参数并帮助解释所得的P波速度模型。在生成的断层图像上，地震速度异常很好地解决了深层沉积盆地，潘尼诺盆地下方的莫霍面地形以及软流圈的相关活动的影响。不同的主要张裂单元和将它们分开的断层带似乎表现出典型的速度异常。