On the Use of High-Resolution Topographic Data as a Proxy for Seismic Site Conditions ( VS 30 ) by
On the Use of High-Resolution Topographic Data as a Proxy for Seismic Site Conditions ( VS 30 ) by
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关于使用高分辨率地形数据作为地震场地条件的代理（VS 30）
DOI：
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发表时间：
2009
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影响因子：
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通讯作者：
D. Wald
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文献类型：
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作者：
T. Allen;D. Wald
最近提出了另一种方法，用于评估全球地震现场条件，或从航天飞机雷达地形使命（SRTM）30角秒数字高程模型（DEM）到30米深度的平均剪切速度（VS 30）。该方法的基本前提是，地形坡度可以作为一个可靠的代理VS30在没有地质和岩土工程为基础的现场条件地图，通过VS30测量和地形坡度之间的相关性。在这里，我们评估使用更高的分辨率（3和9角秒）DEM检查我们是否能够解决VS30更详细的比可以实现使用较低分辨率SRTM数据。分辨率大于30角秒的高质量DEM在全球范围内并不统一。然而，在许多存在此类数据的区域，可利用这些数据来解决地形梯度的更细尺度变化，从而解决VS 30。我们使用美国地质调查局地球资源观测和科学（EROS）数据中心的国家高程数据集（NED），调查使用高分辨率DEM估计VS 30在美国的几个地区，包括加州的旧金山弗朗西斯科湾地区，洛杉矶，加州和圣路易斯，密苏里州。我们将这些结果与台湾台北的一个例子进行比较，该例子使用全球可用的9 arcsec SRTM数据。使用更高分辨率的NED数据恢复了地形梯度的更精细尺度变化，这更好地与地质和地貌特征相关，特别是在丘陵和盆地之间的过渡处，在可用的情况下，使用超过30弧秒的SRTM数据。然而，统计分析表明，与VS30测量相比，低分辨率地形几乎没有改善，这表明一些地形平滑可能会提供更稳定的VS30估计。此外，我们发现，海拔高度的变化，在树冠为基础的SRTM测量分辨率大于30弧秒太大，解决可靠的斜坡，特别是在低梯度沉积盆地。
An alternative method has recently been proposed for evaluating global seismic site conditions, or the average shear velocity to 30 m depth (VS30), from the Shuttle Radar Topography Mission (SRTM) 30 arcsec digital elevation models (DEMs). The basic premise of the method is that the topographic slope can be used as a reliable proxy for VS30 in the absence of geologically and geotechnically based site-condition maps through correlations between VS30 measurements and topographic gradient. Here we evaluate the use of higher-resolution (3 and 9 arcsec) DEMs to examine whether we are able to resolve VS30 in more detail than can be achieved using the lower-resolution SRTM data. High-quality DEMs at resolutions greater than 30 arcsec are not uniformly available at the global scale. However, in many regions where such data exist, they may be employed to resolve finer-scale variations in topographic gradient, and consequently, VS30. We use the U.S. Geological Survey Earth Resources Observation and Science (EROS) Data Center’s National Elevation Dataset (NED) to investigate the use of high-resolution DEMs for estimating VS30 in several regions across the United States, including the San Francisco Bay area in California, Los Angeles, California, and St. Louis, Missouri. We compare these results with an example from Taipei, Taiwan, that uses 9 arcsec SRTM data, which are globally available. The use of higher-resolution NED data recovers finer-scale variations in topographic gradient, which better correlate to geological and geomorphic features, in particular, at the transition between hills and basins, warranting their use over 30 arcsec SRTM data where available. However, statistical analyses indicate little to no improvement over lower-resolution topography when compared to VS30 measurements, suggesting that some topographic smoothing may provide more stable VS30 estimates. Furthermore, we find that elevation variability in canopy-based SRTM measurements at resolutions greater than 30 arcsec are too large to resolve reliable slopes, particularly in low-gradient sedimentary basins.