We derive a three-dimensional shear-wave velocity model of the Ligurian-Provence back-arc basin (Northwestern Mediterranean Sea) using ocean-bottom seismometers (AlpArray OBSs) and land stations from permanent and temporary seismic networks. The quality of OBS continuous records is enhanced by a specific processing that reduces instrumental and seabed-induced noises (transients, tilt, compliance). To further improve the resolution of ambient-noise tomography in the offshore area, we compute the Rayleigh-wave part of the Green functions for OBS-OBS pairs by using onshore stations as virtual sources. 2-D group-velocity maps and their uncertainties are computed in the 4–150 s period range by a transdimensional inversion of Rayleigh-wave travel times. The dispersion data and their uncertainties are inverted for a probabilistic 3-D shear-wave velocity model that includes probability densities for V_s and for the depth of layer interfaces. The probabilistic model is refined by a linearized inversion that accounts for the water layer in the Ligurian Sea. Our S-wave velocity and layer boundary probability models correspond well to a recent, high-resolution P-wave velocity cross-section derived from controlled-source seismic profiling along the Ligurian-Provence basin axis. A joint interpretation of the P- and S-wave velocity sections along this profile reveals a thin, anomalous oceanic crust of low P-wave velocities but high S-wave velocities, intruded by a gabbroic body. The illuminated part of the upper mantle appears to be devoid of serpentinization.

中文翻译：

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利古里亚 - 普罗旺斯盆地环境噪声断层扫描使用 AlpArray 陆上 - 海上网络：海洋域结构的见解

我们使用海底地震仪 (AlpArray OBS) 和来自永久和临时地震网络的陆地台站推导出利古里亚 - 普罗旺斯弧后盆地（西北地中海）的三维剪切波速度模型。OBS 连续记录的质量通过减少仪器和海床引起的噪声（瞬态、倾斜、顺应性）的特定处理得到提高。为了进一步提高近海区域环境噪声层析成像的分辨率，我们通过使用陆上台站作为虚拟源来计算 OBS-OBS 对的格林函数的瑞利波部分。二维群速度图及其不确定性是通过瑞利波传播时间的跨维反演在 4-150 秒周期范围内计算的。V _s和层界面的深度。概率模型通过线性反演进行了细化，该反演解释了利古里亚海的水层。我们的S波速度和层边界概率模型很好地对应于最近的高分辨率P波速度截面，该截面源自沿利古里亚-普罗旺斯盆地轴的受控源地震剖面。沿该剖面对P波和S波速度剖面的联合解释揭示了一个薄的、异常的洋壳，该洋壳具有低P波速度但高S波速度，被辉长岩体侵入。上地幔被照亮的部分似乎没有蛇纹石化。