The most commonly used intensity measure of ground motion in earthquake engineering is the 5% damped spectral ordinate, which varies in different directions. Several different measures have been proposed over the years to combine the intensity of the two horizontal recorded ground motions to derive ground‐motion models as well as for design purposes. This study provides the relation to seven previously used measures of horizontal ground motion with respect to a recently proposed orientation‐independent measure of horizontal ground‐motion intensity referred to as MaxRotD50. This new measure of horizontal intensity is defined as the median value of the maximum spectral ordinate of two orthogonal directions computed for all possible nonredundant orientations. The relations are computed using 5065 pairs of horizontal ground motions taken from the database of ground motions recorded in shallow crustal earthquakes in active tectonic regions developed as part of the Pacific Earthquake Engineering Research Center’s Next Generation Attenuation‐West2 project. Empirically derived period‐dependent relations are presented for three quantities that permit transforming any of the seven other definitions of horizontal ground‐motion intensity to MaxRotD50, namely, (1) geometric mean of the ratio of MaxRotD50 to any of the seven other measures of intensities, (2) standard deviation of the natural logarithm of the ratio of MaxRotD50 to any of the seven other measures of intensities, and (3) the correlation between the natural logarithm of the ratio of MaxRotD50 to the other measures of intensities and the natural logarithm of the other measure of intensity. In addition, the influence of site class at the recording station, earthquake magnitude, and distance to the horizontal projection of the rupture is examined on the geometric mean of the ratio of MaxRotD50 to the median intensity of all nonredundant orientations (i.e., RotD50), showing negligible influence of site class and only a relatively small influence of magnitude and distance.

中文翻译：

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MaxRotD50与实际使用的地震动强度的一些水平分量之间的关系

地震工程中最常用的地震动强度度量是 5% 阻尼谱纵坐标，它在不同方向上变化。多年来，已经提出了几种不同的措施，将两个水平记录的地面运动的强度结合起来，以推导出地面运动模型以及用于设计目的。本研究提供了与最近提出的与方向无关的水平地面运动强度测量值（称为 MaxRotD50）与先前使用的七种水平地面运动测量值的关系。这种新的水平强度度量被定义为为所有可能的非冗余方向计算的两个正交方向的最大光谱纵坐标的中值。这些关系是使用 5065 对水平地面运动计算得出的，这些地面运动取自活跃构造区浅层地壳地震记录的地面运动数据库，该数据库是作为太平洋地震工程研究中心下一代衰减-West2 项目的一部分开发的。给出了三个量的经验导出的周期相关关系，这些量允许将水平地面运动强度的其他七个定义中的任何一个转换为 MaxRotD50，即 (1) MaxRotD50 与其他七个强度度量中的任何一个的比率的几何平均值, (2) MaxRotD50 与其他七种强度测量中的任何一种的比率的自然对数的标准偏差，(3) MaxRotD50 与其他强度量度之比的自然对数与其他强度量度的自然对数之间的相关性。此外，记录台站的站点类别、地震震级和距破裂水平投影的距离对 MaxRotD50 与所有非冗余方向的中值强度（即 RotD50）之比的几何平均值的影响进行了检验，显示站点类别的影响可以忽略不计，并且只有相对较小的幅度和距离影响。