The quality and accuracy of a seismic image can be significantly affected by anisotropy. When anisotropy is significant, neglecting it can lead to smearing of the image, dispositioning of reflections and distortion of amplitudes. Thus, it is imperative to estimate anisotropy and take it into account, especially for long‐offset or wide‐azimuthal seismic data. This study estimates P‐wave anisotropy parameters at the Otway site (Victoria, Australia). A wide range of available offsets acquired within the CO2CRC Otway Project provides a unique opportunity for anisotropy estimation from 3D vertical seismic profile data. We estimate P‐wave anisotropy from direct‐wave arrivals in vertical seismic profile data acquired with geophones and distributed acoustic sensors installed in two wells. Data analysis reveals seismic anisotropy of the subsurface with a significant presence of both polar and azimuthal anisotropy. We estimate key parameters such as normal moveout velocity, azimuthal ellipticity, polar anellipticity and fast‐velocity azimuth by nonlinear fitting of the analytical travel‐time approximation to observed direct P‐wave travel times from 3D vertical seismic profile data. Obtained anisotropy parameters show that polar anellipticity remains almost constant and equal to 0.1 for the whole depth range, while azimuthal anisotropy changes significantly with depth: it is relatively weak in the shallow section then increases significantly below a depth of 600 m. The fast‐velocity azimuth coincides with the orientation of the maximum horizontal stress in the study area. The results show that despite their low sensitivity for large offsets, the distributed acoustic sensor receivers provide sufficient information on anisotropic travel times over the entire length of the well, which is critical for reflection imaging from both vertical seismic profile and surface seismic data.

中文翻译：

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在CO2CRC Otway项目中使用分布式声学传感器和地震检波器从3D垂直地震剖面估算P波各向异性参数

各向异性会严重影响地震图像的质量和准确性。当各向异性很大时，忽略它会导致图像模糊，反射分布和振幅失真。因此，必须估计各向异性并加以考虑，特别是对于长偏移或大方位角地震数据。这项研究估计了奥特威站点（澳大利亚维多利亚）的P波各向异性参数。在CO2CRC Otway项目中获得的大量可用偏移量为从3D垂直地震剖面数据进行各向异性估算提供了独特的机会。我们通过安装在两口井中的地震检波器和分布式声波传感器获取的垂直地震剖面数据中的直接波到达来估计P波各向异性。数据分析显示出地下地震的各向异性，同时存在极性和方位各向异性。我们通过对3D垂直地震剖面数据的分析传播时间近似值与观测到的直接P波传播时间进行非线性拟合，估算出关键参数，例如法向运动速度，方位椭圆率，极地椭圆率和快速速度方位角。所获得的各向异性参数表明，在整个深度范围内，极性极化率几乎保持恒定并等于0.1，而方位角各向异性则随深度而显着变化：在较浅的剖面中它相对较弱，然后在600 m以下深度显着增加。快速速度方位角与研究区域中最大水平应力的方向一致。