284 lines
11 KiB
ReStructuredText
284 lines
11 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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* Measured 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 default parameters for measuring MLc amplitudes can be adjusted by global
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binding parameters:
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* Filtering before instrument simulation: :ref:`BW(3,0.5,12) <filter-bw>`,
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configurable by :confval:`amplitudes.MLc.preFilter`.
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* :term:`Wood-Anderson seismometer` simulation: yes, can be deactivated by
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:confval:`amplitudes.MLc.applyWoodAnderson`.
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* Characteristics of :term:`Wood-Anderson seismometer`: according to IASPEI
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recommendations. Can be adjusted by :confval:`amplitudes.WoodAnderson.gain`,
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:confval:`amplitudes.WoodAnderson.T0`, :confval:`amplitudes.WoodAnderson.h`
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in global bindings or global module configuration.
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* Amplitude scaling: 1, configure by :confval:`amplitudes.MLc.amplitudeScale`
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for considering non-default units by magnitude.
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* Method applied for measuring amplitudes: absolute maximum, configurable in
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global bindings by :confval:`amplitudes.MLc.measureType`.
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* Method for combining amplitude measurements: *max* (maximum from both
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horizontal components), configurable in global bindings by
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:confval:`amplitudes.MLc.combiner`.
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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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* Time window for measuring signal amplitudes [s]: P pick time + 150 s by
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:ref:`scautopick` or distance [km]/3 km/s + 30 s,
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the relevant parameters are: :confval:`amplitudes.MLc.signalBegin`,
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:confval:`amplitudes.MLc.signalEnd`. :ref:`Time grammar <time-grammar>` may be
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applied for begin and end times.
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* Time window for measuring noise amplitudes [s]: 30 s before the P pick,
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the relevant parameters are: :confval:`amplitudes.MLc.noiseBegin`,
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:confval:`amplitudes.MLc.noiseEnd`. :ref:`Time grammar <time-grammar>` may be
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applied for begin and end times.
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* Minimum SNR: 0, configurable by :confval:`amplitudes.MLc.minSNR`.
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* Distance range: 0 - 8 deg, configurable by :confval:`amplitudes.MLc.minDist`,
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:confval:`amplitudes.MLc.maxDist`, stations at distances beyond 8 deg will be strictly
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ignored.
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* Depth range: <= 80 km, can be adjusted and extended by
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:confval:`amplitudes.MLc.minDepth` and :confval:`amplitudes.MLc.maxDepth`.
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Most parameters controlling the amplitude measurements are configurable in
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global bindings or global module configuration.
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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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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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Default properties, most parameters are configurable in global bindings:
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* Distance type: hypocentral, epicentral can be selected by :confval:`magnitudes.MLc.distMode`.
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* Distance range: 0 - 8 deg, configurable by :confval:`magnitudes.MLc.minDist`,
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:confval:`magnitudes.MLc.maxDist`, measurements beyond 8 deg will be strictly
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ignored.
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* Depth range: <= 80 km, can be extended by :confval:`magnitudes.MLc.maxDepth`.
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* Expected amplitude type: MLc, configurable by magnitude alias.
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* Expected amplitude unit: millimeter (mm), other units can be assumed by
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amplitude scaling with :confval:`amplitudes.MLc.amplitudeScale`.
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* Magnitude calibration type: parametric, parametric and non-parametric are
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available through :confval:`magnitudes.MLc.calibrationType`.
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* Calibration function (see below for the equations), configurable by global bindings
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depending on the actual calibration type:
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* parametric: :confval:`magnitudes.MLc.parametric.c0`,
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:confval:`magnitudes.MLc.parametric.c1`,
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:confval:`magnitudes.MLc.parametric.c2`,
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:confval:`magnitudes.MLc.parametric.c3`,
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:confval:`magnitudes.MLc.parametric.c4`,
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:confval:`magnitudes.MLc.parametric.c5`
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* A0: :confval:`magnitudes.MLc.A0.logA0`
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* Station correction: none, configurable by a magnitude-type profile in global
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bindings with :confval:`magnitudes.MLc.offset` or the equivalent in global
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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_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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* *r*: hypocentral (default) or epicentral distance
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* *c1*, *c2*, *c3*, *c4*, *c5*: 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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The default values are valid for SW-Germany (:cite:t:`stange-2006`), c6 and H
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have been added for supporting dependency on depth (:cite:t:`rhoades-2020`).
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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 e.g.
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in :file:`global.cfg`.
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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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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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Magnitude aliases
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-----------------
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Magnitude aliases can be created by :confval:`magnitudes.aliases` in
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global module configuration 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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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:: params
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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:: params
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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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.. note::
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All default values for bindings configuration parameters are from
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:cite:t:`stange-2006`.
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