High-angle or steeply-dipping faults, salt flanks, and subsalt sediments are important structures for many applications such as oil/gas and geothermal energy exploration. However, conventional seismic imaging has poor illuminations in these areas because of using singly scattered waves or primary reflections. By using high-order scattered waves in the reverse time migration (RTM), particularly the secondary scattered waves, we can enhance the seismic illumination for imaging the steep faults and subsalt areas. In our method, we first identify reflection features such as geological layer boundaries and discontinuities, based on the conventional RTM images. We then modify the migration model by adding potential point scatterers into the reflection features. These artificial point scatterers could be randomly placed on and around the reflection features to illuminate the structures where primaries cannot reach. The random placement of the point scatterers differentiates our method from previous methods using duplex or prism waves to image high-angle structures where true reflector locations are particularly identified. In addition, we assign the artificial point scatterers as density perturbations without modifying the velocity model so that they do not affect the spatial position of the imaged reflectors. The proposed method of high-order scattering imaging only requires one additional implementation of RTM but can substantially improve the image quality around high-angle faults and subsalt regions. We verify the effectiveness of our method using two synthetic models, a trapezoidal model and the Sigsbee2B model. And the results demonstrate that our new method produces better images for steep faults and subsalt areas compared with those obtained using conventional RTM.

高角度或陡倾断层，盐翼和盐下沉积物是许多应用的重要结构，例如石油/天然气和地热能勘探。但是，由于使用单个散射波或一次反射，常规地震成像在这些区域的照明度很差。通过在逆时偏移（RTM）中使用高阶散射波（尤其是次级散射波），我们可以增强地震照度，以对陡峭的断层和盐下区域进行成像。在我们的方法中，我们首先根据常规RTM图像识别反射特征，例如地质层边界和不连续性。然后，我们通过将潜在的点散射体添加到反射特征中来修改迁移模型。可以将这些人造点散射体随机放置在反射特征上或反射特征周围，以照亮原色无法到达的结构。点散射体的随机放置使我们的方法与以前使用双工或棱镜波的方法区别开来，可以对特别确定了真实反射器位置的高角度结构进行成像。另外，我们将人工点散射体指定为密度扰动而不修改速度模型，以使它们不影响成像反射器的空间位置。所提出的高阶散射成像方法仅需要RTM的另一种实现方式，但可以显着改善高角度断层和盐下区域周围的图像质量。我们使用两个综合模型验证了我们方法的有效性，梯形模型和Sigsbee2B模型。结果表明，与使用常规RTM相比，我们的新方法对于陡峭断层和盐下区域产生了更好的图像。