The most popular array‐based microtremor survey methods estimate velocity structures from the phase velocities of Rayleigh waves. Using the phase velocity of Love waves improves the resolution of inverted velocity models. In this study, we present a method to estimate the phase velocity of Love waves using rotational array data derived from the horizontal component of microtremors observed using an ordinal nested triangular array. We obtained discretized spatial derivatives from a first‐order Taylor series expansion to calculate rotational motions from observed array seismograms. Rotational motions were obtained from a triangular subarray consisting of three receivers using discretized spatial derivatives. Four rotational‐motion time histories were calculated from different triangular subarrays in the nested triangular arrays. Phase velocities were estimated from the array of the four rotational motions. We applied the proposed Love‐wave phase‐velocity estimation technique to observed array microtremor data obtained using a nested triangular array with radii of 25 and 50 m located at the Institute for Integrated Radiation and Nuclear Science, Kyoto University. The phase velocities of rotational and vertical motions were estimated from the observed data, and results showed that the former were smaller than those of the latter. The observed phase velocities obtained from vertical and rotational components agreed well with the theoretical Rayleigh‐ and Love‐wave phase velocities calculated from the velocity structure model derived from nearby PS logs. To show the ability of the rotation to obtain Love wave, we estimated apparent phase velocities from north–south or east–west components. The apparent velocities resulted in between the theoretical velocities of Rayleigh and Love waves. This result indicates that the calculated rotation effectively derived the Love waves from a combination of Love and Rayleigh waves.

中文翻译：

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基于阵列的旋转运动微震的爱波相位速度估计

最流行的基于阵列的微震勘测方法根据瑞利波的相速度估算速度结构。使用Love波的相速度可以提高反向速度模型的分辨率。在这项研究中，我们提出了一种方法，该方法使用旋转阵列数据来估计Love波的相速度，该旋转阵列数据是使用有序嵌套三角阵列观察到的微震的水平分量得出的。我们从一阶泰勒级数展开中获得了离散的空间导数，以根据观测到的阵列地震图计算出旋转运动。使用离散的空间导数从包含三个接收器的三角形子阵列中获得旋转运动。从嵌套三角阵列中的不同三角子阵列计算出四个旋转运动时间历史。从四个旋转运动的阵列中估计相速度。我们将拟议的洛夫波相速度估计技术应用于观测的阵列微震数据，该观测数据是使用位于京都大学综合辐射与核科学研究所的，半径为25和50 m的嵌套三角阵列获得的。从观察到的数据估计出旋转运动和垂直运动的相速度，结果表明前者小于后者。从垂直和旋转分量获得的观测相速度与从附近PS测井得出的速度结构模型计算得到的理论瑞利和洛夫波相速度非常吻合。为了显示旋转获得爱波的能力，我们估计了南北或东西向分量的表观相速度。表观速度导致瑞利波和洛夫波的理论速度之间的变化。该结果表明，计算出的旋转有效地从Love波和Rayleigh波的组合中得出Love波。