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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:creator>Arthur Frankel</dc:creator>
  <dc:date>1994</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Fourteen &lt;/span&gt;&lt;span class="sc"&gt;GEOS&lt;/span&gt;&lt;span&gt; seismic recorders were deployed in the San Bernardino Valley to study the propagation of short-period (&lt;/span&gt;&lt;i&gt;T&lt;/i&gt;&lt;span&gt; ≈ 1 to 3 sec) surface waves and Moho reflections. Three dense arrays were used to determine the direction and speed of propagation of arrivals in the seismograms. The seismograms for a shallow (&lt;/span&gt;&lt;i&gt;d&lt;/i&gt;&lt;span&gt; ≈ 1 km) &lt;/span&gt;&lt;i&gt;M&lt;/i&gt;&lt;span&gt; 4.9 aftershock of the Big Bear earthquake exhibit a very long duration (60 sec) of sustained shaking at periods of about 2 sec. Array analysis indicates that these late arrivals are dominated by surface waves traveling in various directions across the Valley. Some energy is arriving from a direction 180° from the epicenter and was apparently reflected from the edge of the Valley opposite the source. A close-in aftershock (Δ = 25 km, depth = 7 km) displays substantial short-period surface waves at deep-soil sites. A three-dimensional (3D) finite difference simulation produces synthetic seismograms with durations similar to those of the observed records for this event, indicating the importance of &lt;/span&gt;&lt;i&gt;S&lt;/i&gt;&lt;span&gt;-wave to surface-wave conversion near the edge of the basin. Flat-layered models severely underpredict the duration and spectral amplification of this deep-soil site. I show an example where the coda wave amplitude ratio at 1 to 2 Hz between a deep-soil and a rock site does not equal the &lt;/span&gt;&lt;i&gt;S&lt;/i&gt;&lt;span&gt;-wave amplitude ratio, because of the presence of surface waves in the coda of the deep-soil site. For one of the events studied (Δ ≈ 90 km), there are sizable phases that are critically reflected from the Moho (&lt;/span&gt;&lt;i&gt;PmP&lt;/i&gt;&lt;span&gt; and &lt;/span&gt;&lt;i&gt;SmS&lt;/i&gt;&lt;span&gt;). At one of the rock sites, the &lt;/span&gt;&lt;i&gt;SmS&lt;/i&gt;&lt;span&gt; phase has a more peaked spectrum that the direct &lt;/span&gt;&lt;i&gt;S&lt;/i&gt;&lt;span&gt; wave.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:language>en</dc:language>
  <dc:publisher>Seismological Society of America</dc:publisher>
  <dc:title>Dense array recordings in the San Bernardino Valley of landers-big bear aftershocks: Basin surface waves, Moho reflections, and three-dimensional simulations</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>