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215 lines
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215 lines
12 KiB
HTML
1 year ago
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<!DOCTYPE html>
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<html >
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<head>
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<meta charset="utf-8" />
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<title>mB_BB — SeisComP Release documentation</title>
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<link rel="next" title="mb" href="global_mb.html" />
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<img class="logo" src="../_static/brands/seiscomp/text/white.svg"/>
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<!-- span class="title">SeisComP Release</span -->
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<span class="version">5.3.0</span>
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<a href="../toc/extensions.html" >Extensions</a>
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<a href="../toc/extensions/global.html" accesskey="U">global</a>
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<div class="container">
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<div class="body" role="main">
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<div class="section" id="mb-bb">
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<span id="global-mb-bb"></span><h1>mB_BB<a class="headerlink" href="#mb-bb" title="Permalink to this headline">¶</a></h1>
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<p>Body wave magnitude at teleseismic distances similar to mb</p>
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<div class="section" id="description">
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<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
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<p>The name <strong>mB</strong> is used in <cite>SeisComP</cite> as a synonym for <strong>mB_BB</strong> which is recommended
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by the IASPEI commission (<span id="id1">IASPEI [<a class="reference internal" href="../base/references.html#id40" title="IASPEI. Summary of magnitude working group recommendations on standard procedures for determining earthquake magnitudes from digital data. IASPEI Website, 2013. URL: http://www.iaspei.org/commissions/commission-on-seismological-observation-and-interpretation/Summary_WG_recommendations_20130327.pdf.">43</a>]</span>).</p>
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<p>mB is a magnitude based on body waves like <a class="reference internal" href="global_mb.html#global-mb"><span class="std std-ref">mb</span></a>, but with the amplitude
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measured in a broad
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frequency range and longer time windows. Instead of amplitude measurements on displacement
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data together with the dominant period, the maximum velocity amplitude Vmax is taken
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directly from velocity-proportional records with <img class="math" src="../_images/math/3e38ca2d603956fc616a5148453d32f873cfdbd0.png" alt="V = 2 \pi A/T"/>. The time
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window for the
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measurement can be determined by the duration of the high-frequency (1-3 Hz) radiation
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(<span id="id2">Bormann and Saul [<a class="reference internal" href="../base/references.html#id18" title="P. Bormann and J. Saul. The new iaspei standard broadband magnitude mb. Seismol. Res. Lett., 5:698 - 705, 2008. doi:10.1785/gssrl.79.5.698.">35</a>]</span>). This time window usually contains the phases P, pP, sP, PcP, but
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not PP. According to the long time window and broad frequency range used for amplitude
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measurements mB saturates not like mb.</p>
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<div class="section" id="amplitude">
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<h3>Amplitude<a class="headerlink" href="#amplitude" title="Permalink to this headline">¶</a></h3>
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<p>The mB amplitudes are calculated on vertical-component displacement seismograms
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in accordance with <span id="id3">Bormann and Saul [<a class="reference internal" href="../base/references.html#id18" title="P. Bormann and J. Saul. The new iaspei standard broadband magnitude mb. Seismol. Res. Lett., 5:698 - 705, 2008. doi:10.1785/gssrl.79.5.698.">35</a>]</span> and similar to <a class="reference internal" href="global_mb.html#global-mb"><span class="std std-ref">mb</span></a>.
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A default time window of 60 s is considered for amplitude measurements
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at stations in the distance range of 5° to 105°.
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If the epicentral is known, the length of the time window after the P wave onset is</p>
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<div class="math">
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<p><img src="../_images/math/b79194c277468cc762f2a083243771fd575b5613.png" alt="t = min(11.5 \Delta, 60)"/></p>
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</div><p>where <img class="math" src="../_images/math/6450616b75212cb568e905db49efd0c3dd584648.png" alt="\Delta"/> is the epicentral distance. The methods for measuring
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amplitudes are configurable in the global bindings.</p>
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</div>
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<div class="section" id="station-magnitude">
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<h3>Station Magnitude<a class="headerlink" href="#station-magnitude" title="Permalink to this headline">¶</a></h3>
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<p>The mB station magntiudes are calculated in accordance with <span id="id4">Bormann and Saul [<a class="reference internal" href="../base/references.html#id18" title="P. Bormann and J. Saul. The new iaspei standard broadband magnitude mb. Seismol. Res. Lett., 5:698 - 705, 2008. doi:10.1785/gssrl.79.5.698.">35</a>]</span>.</p>
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<div class="math">
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<p><img src="../_images/math/c4e29d7f89b54eff7de102b648e87d8c0f96afd6.png" alt="mB = \log \left(\frac{A}{2\Pi}\right) + Q(h,\Delta) - 3.0"/></p>
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</div><p>with A as the displacement amplitude in micrometers, T as the dominant period of
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the signal in seconds, Q as a correction term for depth and distance.</p>
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<ul class="simple">
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<li><p>Amplitude unit in <cite>SeisComP</cite>: <strong>nanometers/s</strong> (nm/s),</p></li>
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<li><p>Time window: 60 s if set by <a class="reference internal" href="scautopick.html#scautopick"><span class="std std-ref">scautopick</span></a>, otherwise 0 s - 11.5 * distance
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(deg) with 60 s minimum</p></li>
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<li><p>Default distance range: 5 - 105 deg, configurable: <a class="reference internal" href="global.html#confval-magnitudes.mB.minDist"><code class="xref std std-confval docutils literal notranslate"><span class="pre">magnitudes.mB.minDist</span></code></a>,
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<a class="reference internal" href="global.html#confval-magnitudes.mB.maxDist"><code class="xref std std-confval docutils literal notranslate"><span class="pre">magnitudes.mB.maxDist</span></code></a>,</p></li>
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<li><p>Depth range: no limitation.</p></li>
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</ul>
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<div class="admonition note">
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<p class="admonition-title">Note</p>
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<p>In 2013 the IASPEI commission (<span id="id5">IASPEI [<a class="reference internal" href="../base/references.html#id40" title="IASPEI. Summary of magnitude working group recommendations on standard procedures for determining earthquake magnitudes from digital data. IASPEI Website, 2013. URL: http://www.iaspei.org/commissions/commission-on-seismological-observation-and-interpretation/Summary_WG_recommendations_20130327.pdf.">43</a>]</span>) recommended a minimum
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distance of
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20 deg. However, the calibration formula (<span id="id6">Bormann and Saul [<a class="reference internal" href="../base/references.html#id18" title="P. Bormann and J. Saul. The new iaspei standard broadband magnitude mb. Seismol. Res. Lett., 5:698 - 705, 2008. doi:10.1785/gssrl.79.5.698.">35</a>]</span>) which is
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integrated in
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<cite>SeisComP</cite> allows the extension down to 5 deg while maintaining consistent magnitudes
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at 20 deg and beyond. Therefore, 5 deg is used as the default in
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<a class="reference internal" href="global.html#confval-magnitudes.mB.minDist"><code class="xref std std-confval docutils literal notranslate"><span class="pre">magnitudes.mB.minDist</span></code></a>.</p>
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</div>
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</div>
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<div class="section" id="network-magnitude">
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<h3>Network magnitude<a class="headerlink" href="#network-magnitude" title="Permalink to this headline">¶</a></h3>
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<p>By default, the trimmed mean is calculated from the station magnitudes to form
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the <a class="reference internal" href="../base/glossary.html#term-network-magnitude"><span class="xref std std-term">network magnitude</span></a>. Outliers beyond the outer 12.5% percentiles are
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removed before forming the mean.</p>
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</div>
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<div class="section" id="configuration">
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<h3>Configuration<a class="headerlink" href="#configuration" title="Permalink to this headline">¶</a></h3>
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<p>Adjust the configurable parameters in global bindings in the mB section or use
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<code class="file docutils literal notranslate"><span class="pre">global.cfg</span></code>
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as <a class="reference internal" href="global_mlv.html#global-mlv"><span class="std std-ref">MLv</span></a>. Add mB to the list of computed amplitudes and magnitudes
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in the configuration of
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<a class="reference internal" href="scamp.html#scamp"><span class="std std-ref">scamp</span></a> and <a class="reference internal" href="scmag.html#scmag"><span class="std std-ref">scmag</span></a> and in <a class="reference internal" href="scesv.html#scesv"><span class="std std-ref">scesv</span></a> or <a class="reference internal" href="scolv.html#scolv"><span class="std std-ref">scolv</span></a> for visibility.</p>
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</div>
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</div>
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</div>
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<div id="anchors-bottom"></div>
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<h3 id="searchlabel">Quick search</h3>
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<script>$('#searchbox').show(0);</script>
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<h3><a href="../index.html">Table of Contents</a></h3>
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<ul>
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<li><a class="reference internal" href="#">mB_BB</a><ul>
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<li><a class="reference internal" href="#description">Description</a><ul>
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<li><a class="reference internal" href="#amplitude">Amplitude</a></li>
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<li><a class="reference internal" href="#station-magnitude">Station Magnitude</a></li>
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<li><a class="reference internal" href="#network-magnitude">Network magnitude</a></li>
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<li><a class="reference internal" href="#configuration">Configuration</a></li>
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</ul>
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</li>
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</ul>
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</li>
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</ul>
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<h4>Previous topic</h4>
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<p class="topless"><a href="global_fx-dfx.html"
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title="previous chapter">FX-DFX</a></p>
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<h4>Next topic</h4>
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<p class="topless"><a href="global_mb.html"
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title="next chapter">mb</a></p>
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<h3>This Page</h3>
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Version <b>5.3.0</b> Release
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<div class="copyright">
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Copyright © gempa GmbH, GFZ Potsdam.
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