306 lines
14 KiB
ReStructuredText
306 lines
14 KiB
ReStructuredText
.. _global_mlc:
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###
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MLc
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###
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Custom magnitude for local events measured on horizontal components
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Description
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===========
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MLc is a custom magnitude for local events based on :ref:`ML<global_ml>` but
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with greater flexibility.
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The original implementation is based on specifications by the Hessian Agency for
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Nature Conservation, Environment and Geology, Hessian Earthquake Service.
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More options have been added allowing the magnitude to be configured with
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great flexibility in order to account for many different conditions. The
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general procedures for measuring amplitudes and computing magnitudes are
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outlined in the :ref:`"Concepts" section on magnitudes <concepts_magnitudes>`.
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The MLc magnitude is very similar to the original :ref:`ML<global_ml>`,
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except that
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* Amplitude pre-filtering is applied by default.
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* Wood-Anderson simulation is optionally applied and can be deactivated.
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* Measured amplitudes can be scaled accounting for expected units.
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* Measured amplitudes are combined by taking the maximum instead of the average.
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* A parametric :ref:`magnitude calibration <mlc_station_magnitude>` function
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applies but a correction in the form log10(A0) can be configured for converting
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measured amplitudes to station magnitudes.
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* Hypocentral instead of epicentral distance is considered by default.
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Amplitudes
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----------
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Some general conditions apply for measuring amplitudes:
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* Name amplitude type: MLc.
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* Expected unit of gain-corrected input data: m/s. Activate response correction
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in global bindings in case data are provided in acceleration.
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* Components used for amplitude measurements: both horizontal components
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separately.
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The parameters for measuring MLc amplitudes can be adjusted by global
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binding parameters:
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.. csv-table::
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:widths: 20 25 15 30
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:header: Topic, Parameter, Default, Comment
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:align: left
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:delim: ;
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:ref:`Filtering <filter-grammar>`; :confval:`amplitudes.MLc.preFilter`; :ref:`BW(3,0.5,12) <filter-bw>`; Applied before instrument simulation
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:term:`Wood-Anderson simulation <Wood-Anderson seismometer>`; :confval:`amplitudes.MLc.applyWoodAnderson`; true; When WA simulation is inactive, measured amplitudes take the units of the gain of the stream on which they were measured.
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:term:`Wood-Anderson parameters <Wood-Anderson seismometer>`; :confval:`amplitudes.WoodAnderson.gain`, :confval:`amplitudes.WoodAnderson.T0`, :confval:`amplitudes.WoodAnderson.h`; 2080, 0.8, 0.7; Defaults: see :ref:`IASPEI recommendation <concepts_magnitudes-wa>`.
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Amplitude scaling; :confval:`amplitudes.MLc.amplitudeScale`; 1; Apply for scaling measured amplitudes to units required by the magnitude
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Amplitude combination; :confval:`amplitudes.MLc.combiner`;max; Method for combining amplitudes measured on both horizontal components
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Some additional parameters require you to create an amplitude-type profile for
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global binding parameters. Name the profile like the amplitude name, hence MLc
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replacing '$name' in the parameters below:
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.. csv-table::
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:widths: 20 25 15 30
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:header: Topic, Parameter, Default, Comment
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:align: left
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:delim: ;
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Minimum distance; :confval:`amplitudes.$name.minDist`; 0;
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Maximum distance; :confval:`amplitudes.$name.maxDist`; 8; Cannot be extended beyond default
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Minimum source depth; :confval:`amplitudes.$name.minDepth`; 0; Can be negative
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Maximum source depth; :confval:`amplitudes.$name.maxDepth`; 80; Can be extended beyond default
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Noise window begin; :confval:`amplitudes.$name.noiseBegin`; -30; (+++)
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Noise window end; :confval:`amplitudes.$name.noiseEnd`; -5; (+++)
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Signal window begin; :confval:`amplitudes.$name.signalBegin`; -5; (+++)
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Signal window end; :confval:`amplitudes.$name.signalEnd`; 150 (+) or distance/3+30 (++); (**+**) When measured by :ref:`scautopick`, (**++**) When measured by :ref:`scamp` or :ref:`scolv` (+++)
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Minimum :term:`SNR`; :confval:`amplitudes.$name.minSNR`;not applied; Compares the maximum amplitudes measured within the signal and noise windows
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Period range; NA; NA; Period is not measured. A configuration will prevent any MLc amplitude from being measured
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Amplitude saturation; :confval:`amplitudes.$name.saturationThreshold`; false; Apply for avoiding measurements on clipped data
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Response correction; :confval:`amplitudes.$name.enableResponses`; false; Activate for input units other than nm/s and set :confval:`amplitudes.$name.resp.minFreq`, :confval:`amplitudes.$name.resp.maxFreq`
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**(+++)** All values defining the time windows for measuring noise and signal
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are relative to P arrival time, read :ref:`Time grammar <time-grammar>`.
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The default values are valid for SW-Germany (:cite:t:`stange-2006`).
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The Wood-Anderson simulation will convert input velocity data to ground
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displacement in mm. The input data may be of a different unit after applying
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:confval:`amplitudes.MLc.preFilter`, e.g. when integration is applied, and / or
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when Wood-Anderson simulation is disabled. Configure
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:confval:`amplitudes.MLc.amplitudeScale` for converting the unit of the
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processed data to the unit expected by the
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:ref:`station magnitude calibration <mlc_station_magnitude>` for the measured
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amplitude.
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.. note::
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For comparing MLc amplitudes with :ref:`ML amplitudes <global_ml>` set the
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global bindings parameters
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.. code-block:: properties
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amplitudes.MLc.preFilter = ""
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amplitudes.MLc.combiner = average
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.. _mlc_station_magnitude:
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Station magnitudes
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------------------
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Station magnitudes are computed from measured amplitudes by applying a
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configurable calibration function when the origin is within depths and distance
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constraints. The parameters are configurable in global bindings or by global
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module parameters when applying
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:ref:`regionalization <concepts-magnitudes-regionalization>`.
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Station corrections are configurable by a magnitude-type profile named MLc in
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global bindings with :confval:`magnitudes.$name.offset` or the equivalent in
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global module configuration as :confval:`module.trunk.NET.STA.magnitudes.MLc.offset`.
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The latter is not supported by :ref:`scconfig` but it reduces the amount of
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required bindings.
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The calibration function is considered in one of the forms
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* Parametric when :confval:`magnitudes.MLc.calibrationType` = "parametric"`:
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.. math::
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MLc = \log_{10}(A) + c_7 * e^{c8 * r} + c_6 * h + c_3 * \log_{10}(r / c_5) + c_2 * (r + c_4) + c_1 + c_0(station)
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where
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* *A*: displacement amplitude measured in unit of mm or as per configuration
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* *c1 - c8*: general calibration parameters
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* *c0*: station-specific correction
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* *r*: Hypocentral (default) or epicentral distance as configured by
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:confval:`magnitudes.MLc.distMode`
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* h: (source depth - :confval:`magnitudes.MLc.parametric.H`) when
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source depth > :confval:`magnitudes.MLc.parametric.H` but 0 otherwise.
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The default values are valid for SW-Germany (:cite:t:`stange-2006`). *c6*,
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*H* have been added for supporting dependency on depth (:cite:t:`rhoades-2020`)
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and *c7*, *c8* for observations at short distances (:cite:t:`luckett2019`).
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* log10(A0)-based non-parametric when :confval:`magnitudes.MLc.calibrationType` = "A0"`:
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.. math::
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MLc = \log_{10}(A) - \log_{10}(A_0)
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where
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* :math:`log_{10}(A_0)`: distance-dependent correction value. Read
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:ref:`global_mlv` for the details.
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.. note::
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* The magnitude calibration function can be regionalized by adjusting global
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module configuration parameters in MLc region profiles of
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:confval:`magnitudes.MLc.region.*` and in a *MLc* Magnitude type profile
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e.g., in :file:`global.cfg`.
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Configurable parameters:
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.. csv-table::
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:widths: 20 25 15 30
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:header: Topic, Parameter, Default, Comment
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:align: left
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:delim: ;
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Distance type; :confval:`magnitudes.MLc.distMode`; hypocentral; epicentral or hyocentral can be selected
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Minimum distance; :confval:`magnitudes.MLc.minDist`; -1;
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Maximum distance; :confval:`magnitudes.MLc.maxDist`; 8; Measurements beyond 8 deg are strictly ignored
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Minimum source depth; :confval:`magnitudes.MLc.minDepth`; -10;
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Maximum source depth; :confval:`magnitudes.MLc.maxDepth`; 80; Can be extended beyond default
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Period range; NA; NA; Period is not measured. A configuration will prevent any MLc magnitude from being computed
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Amplitude type;; MLc; Configurable by :ref:`amplitude and magnitude alias <concepts_magnitudes-aliases>`
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Amplitude unit;; mm; other units can be assumed by amplitude scaling with :confval:`amplitudes.MLc.amplitudeScale`
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Magnitude calibration type; :confval:`magnitudes.MLc.calibrationType`; parametric; parametric and A0 (non-parametric) are available
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Linear magnitude correction;:confval:`magnitudes.$name.multiplier`; 1.0; Configure station corrections more conveniently configurable in global module configuration as :confval:`module.trunk.NET.STA.magnitudes.MLc.multiplier`
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Constant magnitude correction;:confval:`magnitudes.$name.offset`; 0.0; Configure station corrections more conveniently configurable in global module configuration as :confval:`module.trunk.NET.STA.magnitudes.MLc.offset`
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;;;
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**parametric** calibration;;; Parameters are used for :confval:`magnitudes.MLc.calibrationType` = parametric
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;:confval:`magnitudes.MLc.parametric.c0`;0.0;
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;:confval:`magnitudes.MLc.parametric.c1`;0.69;
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;:confval:`magnitudes.MLc.parametric.c2`;0.00095;
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;:confval:`magnitudes.MLc.parametric.c3`;1.11;
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;:confval:`magnitudes.MLc.parametric.c4`;0.0;
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;:confval:`magnitudes.MLc.parametric.c5`;1.0;
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;:confval:`magnitudes.MLc.parametric.c6`;0.0; see :cite:t:`rhoades-2020`
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;:confval:`magnitudes.MLc.parametric.H`;40.0; see :cite:t:`rhoades-2020`
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;:confval:`magnitudes.MLc.parametric.c7`;0.0; see :cite:t:`luckett2019`
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;:confval:`magnitudes.MLc.parametric.c8`;0.0; see :cite:t:`luckett2019`
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;;;
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**non-parametric** calibration;;; Parameters are used for :confval:`magnitudes.MLc.calibrationType` = A0
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;:confval:`magnitudes.MLc.A0.logA0`;0:-1.3,60:-2.8,100:-3.0,400:-4.5,1000:-5.85; from :ref:`ML magnitude <global_ml>`
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Network magnitude
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-----------------
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The network magnitude is computed from station magnitudes automatically by
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:ref:`scmag` or interactively by :ref:`scolv`.
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Originally the median was computed from all station MLc to form the
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:term:`network magnitude` MLc. Here, the trimmed mean is applied. Outliers
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beyond the outer 12.5% percentiles are removed before forming the mean. The
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method can be adjusted in :ref:`scmag` by :confval:`magnitudes.average`.
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Moment magnitude
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----------------
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MLc can be scaled to a moment magnitude, Mw(MLc), by a magnitude-type profile in
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global module configuration. Read the
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:ref:`Tutorial on moment magnitudes <tutorials_mags_moment>` for the details.
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Aliases
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-------
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Amplitude and magnitude aliases can be created by :confval:`magnitudes.aliases`
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and :confval:`amplitudes.aliases`, respectively, in global module configuration
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in order to derive other magnitude types from
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original amplitudes and magnitudes. The actual amplitude and magnitude
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parameters of the aliases will be configured in global bindings or by
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magnitude-type profiles in global module configuration. Read the
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:ref:`Tutorial on magnitude aliases <tutorials_magnitude-aliases>` for the
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details.
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Regionalization
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---------------
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Regionalization may be achieved by a magnitude-type profile in global module
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configuration. Read the
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:ref:`Tutorial on regionalization <tutorials_magnitude-region>` for the details.
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Examples
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========
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The flexibility of the amplitude and magnitude processing allows for MLc to be
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applied in various use cases. Examples are given below.
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* **Default:** Pre-filtered and gain-corrected amplitudes, Wood-Anderson
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corrected and measured in mm for Southwestern Germany, :cite:t:`stange-2006`:
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.. math::
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MLc = \log_{10}(A) + 1.11 * \log_{10}(r) + 0.00095 * r + 0.69 + c_0
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* Wood-Anderson-corrected displacement amplitudes measured in mm for
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Southern California, :cite:t:`hutton-1987`:
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.. math::
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MLc = \log_{10}(A) + 1.110 * \log_{10}(r / 100) + 0.00189 * (r - 100) + 3.0
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* Pre-filtered velocity amplitudes in units of mym/s (requiring to set
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:confval:`amplitudes.MLc.amplitudeScale`), no Wood-Anderson correction,
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for West Bohemia, e.g. :cite:t:`hiemer-2012`:
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.. math::
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MLc = \log_{10}(A) - log_{10}(2\Pi) + 2.1 * \log_{10}(r) - 1.7 + c_0
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.. figure:: media/magnitude-calibrations_MLc_s_MLc_hb.png
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:align: center
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:width: 18cm
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MLc magnitudes for measured amplitude of 1 mm with default magnitude
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calibration (*MLc_s*, :cite:t:`stange-2006`) and calibration values for Southern
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California (*MLc_hb*, :cite:t:`hutton-1987`).
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Setup
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=====
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#. **Set the configuration and calibration parameters** in the global bindings
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similar
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to :ref:`global_ml`. Instead of configuring lots of global bindings profiles
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or station bindings one line per parameter can be added to the global module
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configuration (:file:`global.cfg`) which takes the form
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.. code-block:: properties
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module.trunk.NET.STA.amplitudes.MLc.preFilter = value
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module.trunk.NET.STA.magnitudes.MLc.parametric.c0 = value
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#. Add MLc to the list of default amplitudes and magnitudes if MLc is to be
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computed by automatic modules, e.g. of :ref:`scamp`, :ref:`scmag`.
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#. Configure :ref:`scmag` (:confval:`magnitudes.average` in :file:`scmag.cfg`)
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for choosing the method to form the
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network magnitude from station magnitudes, e.g.
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.. code-block:: properties
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magnitudes.average = MLc:median
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#. Add MLc to the list of magnitudes preferred by :ref:`scevent`
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(:confval:`eventAssociation.magTypes` in :file:`scevent.cfg`) in order to let
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MLc become the preferred magnitude.
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#. Set defaults/visibility of MLc in :term:`GUI` modules, e.g. :ref:`scolv`
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or :ref:`scesv`.
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