A method discussed in Gibbs, Boore, et al. (1994) was applied to surface‐source, downhole‐receiver recordings at 22 boreholes, in the San Francisco Bay area in central California and the San Fernando Valley of southern California, to determine the average damping ratio of shear waves over depth intervals ranging from about 10 m to as much as 245 m (at one site), with most maximum depths being between 35 and 90 m. The average damping values range from somewhat less than 1% to almost 8%, with little dependence on grain size for sites in sediments. Surprisingly, the average damping values for sites with average velocities greater than about 450 m/s⁠, including, but not limited to rock sites, are generally larger than for sites with lower average velocities. The combined effect of the higher damping and shorter travel times through the rock columns, however, leads to an effective attenuation that is generally comparable or smaller than for soil sites.

中文翻译：

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来自加利福尼亚中部旧金山湾区和南加利福尼亚圣费尔南多谷 22 个地点的表面源、井下接收器测量的阻尼值

Gibbs、Boore 等人中讨论的一种方法。(1994) 应用于加利福尼亚中部旧金山湾区和加利福尼亚南部圣费尔南多河谷 22 个钻孔的表面源、井下接收器记录，以确定横波在深度间隔范围内的平均阻尼比大约 10 m 到 245 m（在一个站点），大多数最大深度在 35 到 90 m 之间。平均阻尼值的范围从略小于 1% 到几乎 8%，几乎不依赖沉积物中的颗粒大小。令人惊讶的是，平均速度大于约 450 m/s 的站点（包括但不限于岩石站点）的平均阻尼值通常大于平均速度较低的站点。更高的阻尼和更短的通过岩柱的行程时间的综合效果，