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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>David Boore</dc:contributor>
  <dc:creator>Linda Al Atik</dc:creator>
  <dc:date>2024</dc:date>
  <dc:description>&lt;p&gt;The square-root-impedance (SRI) method is commonly used to approximate the seismic site amplifications computed using the full-resonance (FR) method for gradient shear-wave velocity (&lt;i&gt;V&lt;sub&gt;S&lt;/sub&gt;&lt;/i&gt;) profiles that are smoothly varying with depth. The SRI site amplifications have been observed to systematically underpredict the FR site amplifications by a ratio of FR/SRI amplifications around 1.05 to 1.3 across a wide&amp;nbsp; frequency range (Boore, 2013). Recently, Boore and Abrahamson (2023; hereafter, BA23) related this difference in the SRI and FR methods to differences in the exponent η of the ratio of seismic impedances between the two methods. They proposed the implementation of a modified frequency-dependent η in the SRI method to improve its match to the FR site amplifications. This modified η was derived using only five &lt;i&gt;V&lt;sub&gt;S&lt;/sub&gt;&lt;/i&gt; profiles. We investigate the performance of the BA23 η for a wide range of realistic gradient &lt;i&gt;V&lt;sub&gt;S&lt;/sub&gt;&lt;/i&gt; profiles with &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;S30&lt;/sub&gt; ranging from 180 to 1500 m/s. These gradient &lt;i&gt;V&lt;sub&gt;S&lt;/sub&gt;&lt;/i&gt; profiles are constructed using two power-law functions of depth and are constrained by the assigned VS30 value, the depth and velocity of the half-space, and depths to shear-wave velocity horizons of 1.0 and 2.5 km/s (&lt;i&gt;Z&lt;/i&gt;&lt;sub&gt;1.0&lt;/sub&gt; and &lt;i&gt;Z&lt;/i&gt;&lt;sub&gt;2.5&lt;/sub&gt;) based on western United States sites. Despite observing a &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;S30&lt;/sub&gt;&amp;nbsp;dependence of η, we find that the BA23 η generally works reasonably well for the range of &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;S&lt;/sub&gt; profiles analyzed. Using the &lt;i&gt;VS30&lt;/i&gt;-dependent η derived in this study results in improvements in matching the FR site amplification compared to using the BA23 η. These improvements are more pronounced for the soft-site conditions and become modest to negligible for the stiff site conditions&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1785/0120240112</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Seismological Society of America</dc:publisher>
  <dc:title>Extending the Boore and Abrahamson (2023) modified square-root-impedance method for the development of site amplifications consistent with the full-resonance approach to a range of VS30 values</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>