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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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<div class="section" id="md">
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<span id="global-md"></span><h1>Md<a class="headerlink" href="#md" title="Permalink to this headline">¶</a></h1>
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<p>Duration magnitude plugin</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 duration magnitude is based on coda duration measurement.
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It’s usually valid for small earthquakes up to magnitude 4 to 5.</p>
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<p>First used in 1972 by Lee et al., Duration magnitude (Md) or Coda duration
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magnitude plugin estimates Richter magnitude of local earthquakes by using
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signal duration on vertical components of seismographs.</p>
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<p>Estimations are quite stable for local earthquakes ranging from magnitude
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Md 0.0 to 5.0.</p>
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<div class="section" id="amplitude-processing">
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<h3>Amplitude processing<a class="headerlink" href="#amplitude-processing" title="Permalink to this headline">¶</a></h3>
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<p>Duration magnitude is usually computed on short period seismometers by searching
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the time at which the amplitude of the signal is close to pre-earthquake amplitude.</p>
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<p>Since it’s mainly used for small earthquake whose signal is at rather high frequency,
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it’s usefull to highpass filter broadband seismomters (select sismo type 6 and a
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Butterworth filter “3,1.5”).
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Or a better solution is to deconvolve the signals and reconvolve with a widely used
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short-period instrument : the 1Hz eigen-frequency L4C (select sismo type 9).
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If you have the full responses in your inventory and have activated them
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(amplitudes.enableResponses set to true), you will be able to use also accelerometers.</p>
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<p>The plugin then searches for the maximum amplitude of the signal, which should be
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the S-wave and then computed mean amplitude of one-second time windows.
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As soon as a one-second time window mean amplitude vs pre-earthquake amplitude
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reaches the configured SNR ratio, the process is stopped.
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The middle of the one-second time window is assumed to be the end of the Coda and
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the time difference between Coda time and P arrival time is stored as Coda duration.</p>
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</div>
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<div class="section" id="magnitude-processing">
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<h3>Magnitude processing<a class="headerlink" href="#magnitude-processing" title="Permalink to this headline">¶</a></h3>
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<p>Once amplitudes calculated by the AmplitudeProcessor and a Coda has been found,
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the generic formula is applied and the duration magnitude is computed
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for a given station, if it fits the criteria (max depth, max distance).</p>
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<div class="math">
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<p><img src="../_images/math/a3010f147479b84f14b15be9438d4940ab36bca0.png" alt="mag = FMA + FMB \times \log10(period) + (FMF \times period) + (FMD \times epidistkm) + (FMZ \times depth) + STACOR"/></p>
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<div class="section" id="plugin">
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<h2>Plugin<a class="headerlink" href="#plugin" title="Permalink to this headline">¶</a></h2>
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<p>The Coda duration magnitude plugin (Md) is installed under <code class="file docutils literal notranslate"><span class="pre">share/plugins/md.so</span></code>.
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It provides a new implementations of AmplitudeProcessor and MagnitudeProcessor.</p>
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<p>To add the plugin to a module add it to the modules configuration, either
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<code class="file docutils literal notranslate"><span class="pre">modulename.cfg</span></code> or <code class="file docutils literal notranslate"><span class="pre">global.cfg</span></code>:</p>
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<div class="highlight-sh notranslate"><div class="highlight"><pre><span></span><span class="nv">plugins</span> <span class="o">=</span> <span class="si">${</span><span class="nv">plugins</span><span class="si">}</span>, md
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</pre></div>
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</div>
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<p>Basically it can be used by modules: <a class="reference internal" href="scamp.html#scamp"><span class="std std-ref">scamp</span></a>, <a class="reference internal" href="scmag.html#scmag"><span class="std std-ref">scmag</span></a>, <a class="reference internal" href="scolv.html#scolv"><span class="std std-ref">scolv</span></a>.</p>
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<div class="section" id="more-information">
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<h3>More information<a class="headerlink" href="#more-information" title="Permalink to this headline">¶</a></h3>
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<p>Description of the formula can be found in Hypo2000 manual from USGS website.
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<a class="reference external" href="http://earthquake.usgs.gov/research/software/#HYPOINVERSE">http://earthquake.usgs.gov/research/software/#HYPOINVERSE</a></p>
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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="#">Md</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-processing">Amplitude processing</a></li>
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<li><a class="reference internal" href="#magnitude-processing">Magnitude processing</a></li>
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<li><a class="reference internal" href="#plugin">Plugin</a><ul>
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<li><a class="reference internal" href="#more-information">More information</a></li>
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Version <b>5.3.0</b> Release
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Copyright © gempa GmbH, GFZ Potsdam.
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