SEISMIC TRAVELTIME INVERSION FOR 2-D CRUSTAL VELOCITY STRUCTURE
SEISMIC TRAVELTIME INVERSION FOR 2-D CRUSTAL VELOCITY STRUCTURE
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DOI：
10.1111/j.1365-246x.1992.tb00836.x
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发表时间：
1992-01-01
影响因子：
2.8
通讯作者：
SMITH, RB
中科院分区：
文献类型：
--
作者：
ZELT, CA;SMITH, RB
本文提出了一种同时确定二维速度和界面结构的地震走时反演方法，该方法适用于任何类型的体波地震资料。 与试错法正演模型相比，反演的优点是，它提供了对模型参数分辨率、不确定性和非唯一性的估计，并保证数据是按照规定的标准拟合的。 此外，解释数据所需的时间也大大减少。 反演方案是迭代的，并且基于模型参数化和适合于逆方法的前向步骤的射线追踪方法。 速度和边界节点的数量和位置可以适应于炮点接收器几何形状和地下射线覆盖，以及近地表的复杂性。 模型参数化还允许使用辅助振幅信息来约束仅由走时数据不能充分解决的模型特征。 射线追踪的方法使用射线追踪方程的有效数值解、起飞角度的自动确定以及产生更稳定的反演结果的平滑层边界的模拟。 在射线追踪过程中，分析计算旅行时相对于速度和边界节点深度的偏导数，并使用阻尼最小二乘技术来确定更新的参数值，同时确定速度和边界深度。 停止标准和最佳数量的速度和边界节点是基于RMS走时残差和参数分辨率之间的权衡，以及跟踪射线到所有观测的能力。 空间分辨率和绝对参数不确定性的估计方法。 一个使用合成数据的例子证明了该算法的准确性，快速收敛和对实际噪声水平的敏感性。 1986年IRIS-PASSCAL内华达州，美国（盆地和山脉省）地震实验的折射和广角反射走时反演说明了处理真实的数据所需的方法和实际考虑。 我们最终的2-D速度模型与使用其他1-D和2-D正演和反演方法的研究结果进行比较，作为对反演方案有效性的检查，并提供了参数不确定性的估计，这些参数不确定性说明了建模方法和解释器引入的偏差。
A method of seismic traveltime inversion for simultaneous determination of 2-D velocity and interface structure is presented that is applicable to any type of body-wave seismic data. The advantage of inversion, as opposed to trial-and-error forward modelling, is that it provides estimates of model parameter resolution, uncertainty and non-uniqueness, and an assurance that the data have been fit according to a specified norm. In addition, the time required to interpret data is significantly reduced. The inversion scheme is iterative and is based on a model parametrization and a method of ray tracing suited to the forward step of an inverse approach. The number and position of velocity and boundary nodes can be adapted to the shot-receiver geometry and subsurface ray coverage, and to the complexity of the near-surface. The model parametrization also allows ancillary amplitude information to be used to constrain model features not adequately resolved by the traveltime data alone. The method of ray tracing uses an efficient numerical solution of the ray tracing equations, an automatic determination of take-off angles, and a simulation of smooth layer boundaries that yields more stable inversion results. The partial derivatives of traveltime with respect to velocity and the depth of boundary nodes are calculated analytically during ray tracing and a damped least-squares technique is used to determine the updated parameter values, both velocities and boundary depths simultaneously. The stopping criteria and optimum number of velocity and boundary nodes are based on the trade-off between RMS traveltime residual and parameter resolution, as well as the ability to trace rays to all observations. Methods for estimating spatial resolution and absolute parameter uncertainty are presented. An example using synthetic data demonstrates the algorithm's accuracy, rapid convergence and sensitivity to realistic noise levels. An inversion of refraction and wide-angle reflection traveltimes from the 1986 IRIS-PASSCAL Nevada, USA (Basin and Range province) seismic experiment illustrates the methodology and practical considerations necessary for handling real data. A comparison of our final 2-D velocity model with results from studies using other 1-D and 2-D forward and inverse methods serves as a check on the validity of the inversion scheme and provides estimates of parameter uncertainties that account for the bias introduced by the modelling approach and the interpreter.