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158 lines
4.5 KiB
Plaintext
158 lines
4.5 KiB
Plaintext
1 year ago
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.. _global_mlv:
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###
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MLv
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###
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Local (Richter) magnitude measured on the vertical component
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Description
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===========
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MLv is the local (Richter) magnitude (:cite:t:`richter-1935`) computed from amplitudes measured on the
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vertical component.
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General (default) conditions apply:
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* Amplitude unit in SeisComP: **millimeter** (mm) by Wood-Anderson simulation.
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* Time window: 150 s by :ref:`scautopick` or distance dependent, configurable.
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* Default distance range: 0 - 8 deg, maximum is configurable
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:confval:`magnitudes.MLv.maxDistanceKm`, measurements beyond 8 deg will be
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strictly ignored.
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* Depth range: no limitation.
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Amplitudes
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----------
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The MLv amplitude calculation is very similar to the original :ref:`ML<global_ml>`,
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except that the amplitude is measured on the vertical component. The methods
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for measuring amplitudes are configurable in the global bindings.
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Station Magnitudes
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------------------
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The individual station MLv is calculated up to the epicentral distance
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:confval:`magnitudes.MLv.maxDistanceKm` using the following formula:
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.. math::
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MLv = \log10(A) - \log10(A0)
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A is the MLv Wood-Anderson amplitude in millimeters. The second term
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is the empirical calibration function, which in turn is a function
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of the epicentral distance (see :cite:t:`richter-1935`). This calibration
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function can be configured globally or per station using global
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bindings or the global module configuration variable
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module.trunk.global.magnitudes.MLv.logA0 in :file:`global.cfg`, e.g. ::
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module.trunk.global.magnitudes.MLv.logA0 = "0:-1.3,60:-2.8,100:-3.0,400:-4.5,1000:-5.85"
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module.trunk.global.magnitudes.MLv.maxDistanceKm = "-1"
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The logA0 configuration string consists of an arbitrary number of
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distance-value pairs separated by semicolons. The distance is in km
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and the value corresponds to the *log10(A0)* term above.
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Within each interval the values are computed by linear
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interpolation. E.g. for the above default specification, at a
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distance of 80 km the *log10(A0)* value would be
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.. math::
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\log10(A0) &= ((-3.0)-(-2.8))*(80-60)/(100-60)-2.8 \\
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&= -2.9
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In other words, at 80 km distance the magnitude would be
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.. math::
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MLv &= \log10(A) - (-2.9) \\
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&= \log10(A) + 2.9
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which is according to the original Richter formula :cite:p:`richter-1935` if the
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amplitude is measured in millimeters.
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Network magnitude
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-----------------
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By default, the trimmed mean is calculated from the station magnitudes to form
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the :term:`network magnitude`. Outliers beyond the outer 12.5% percentiles are
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removed before forming the mean.
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Configuration
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-------------
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Several distance-value pairs can be configured for different ranges of
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epicentral distance.
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The calibration function and maximum distance can be configured globally,
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per network or per station using the configuration variables. Instead configuring
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lots of global bindings profiles or station bindings one line per parameter can be
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added to the global module configuration (:file:`global.cfg`), e.g.
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global:
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.. code-block:: sh
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module.trunk.global.magnitudes.MLv.logA0 = "0:-1.3,60:-2.8,100:-3.0,400:-4.5,1000:-5.85"
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module.trunk.global.magnitudes.MLv.maxDistanceKm = -1
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or per network:
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.. code-block:: sh
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module.trunk.GR.magnitudes.MLv.logA0 = "0:-1.3,60:-2.8,100:-3.0,400:-4.5,1000:-5.85"
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module.trunk.GR.magnitudes.MLv.maxDistanceKm = -1
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or per station:
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.. code-block:: sh
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module.trunk.GR.MOX.magnitudes.MLv.logA0 = "0:-1.3,60:-2.8,100:-3.0,400:-4.5,1000:-5.85"
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module.trunk.GR.MOX.magnitudes.MLv.maxDistanceKm = -1
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Set the configuration and calibration parameters in the global bindings. By
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default MLv is computed by :ref:`scautopick` and is visible in GUIs.
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.. _global_mlv_configuration:
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Module Configuration
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====================
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.. note::
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**magnitudes.MLv.\***
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*Regional calibration parameters for MLv. The region itself is defined*
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*by another magnitude-type MLv profile.*
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.. note::
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**magnitudes.MLv.region.\***
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*Add one profile for every region. The profile name*
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*equals the name of a polygon configured in the BNA file*
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*of the Magnitude-type profile. The Magnitude-type profile*
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*and the polygon must exist.*
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*The special name "world" corresponds to the*
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*region of the entire planet as a fallback.*
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.. note::
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**magnitudes.MLv.region.$name.\***
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$name is a placeholder for the name to be used.
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.. confval:: magnitudes.MLv.region.$name.logA0
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Type: *string*
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Overrides the calibration function log10\(A0\)
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for computing MLv per region. See logA0
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description in the bindings.
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