Ms_20

Surface wave magnitude measured at around 20 s

Description

Ms_20 is the surface wave magnitude measured on the vertical component at around 20 s period in accordance with the IASPEI standards. Please read the specifications in IASPEI [54].

Amplitude

The Ms_20 amplitudes are measured on vertical-component displacement seismograms corrected for the instrument response of a WWSSN_LP seismograph. For configuration of amplitude measurement create and configure an Ms_20-named amplitude-type profile in global bindings. Bindings configuration parameters (replace $name by Ms_20):

• Time window: max(OT+R/4,-5) - min(OT+R/3,3000), configurable: amplitudes.$name.signalBegin and amplitudes.$name.signalEnd.

• Period range: 18 s - 22 s, configurable: amplitudes.$name.minPeriod, amplitudes.$name.maxPeriod. Some agencies extend the range up to 12 s - 28 s.

• Default distance range: 20 - 160 deg, configurable: amplitudes.$name.minDist, amplitudes.$name.maxDist,

• Depth range: <= 100 km, configurable: amplitudes.$name.minDepth, amplitudes.$name.maxDepth,

• Signal-to-noise ration: 0, configurable: amplitudes.$name.minSNR,

• Clipped seismograms: false, configurable: amplitudes.$name.saturationThreshold.

Note

The bindings configuration parameters magnitudes.Ms_20.minVelocity and magnitudes.Ms_20.maxVelocity are obsolete, not considered anymore and replaced by amplitudes.$name.signalBegin and amplitudes.$name.signalEnd, respectively.

Station Magnitude

Ms_20 is the surface-wave magnitude at 20 s period based on the recommendations by the IASPEI magnitude working group issued on 27 March, 2013 (IASPEI [54]).

with

• A: WWSSN_LP corrected ground displacement in units of nm measured on the vertical-component seismogram as the maximum absolute trace amplitude of a surface wave at periods between 18 s and 22 s,

• T: period of the surface wave in seconds.

The term Ms_20 is chosen in accordance with the IASPEI standard as of 2013 (IASPEI [54]). Alternatively, the term Ms(20) may be used. For configuration of magnitude computation create and configure an Ms_20-named magnitude-type profile in global bindings. Bindings configuration parameters (replace $name by Ms_20):

• Amplitude unit: nm, ground displacement corrected for WWSSN_LP

• Period range: 18 s - 22 s, configurable: magnitudes.$name.minPeriod, magnitudes.$name.maxPeriod. Some agencies extend the range up to 12 s - 28 s.

• Default distance range: 20 - 160 deg, configurable: magnitudes.$name.minDist, magnitudes.$name.maxDist

• Depth range: <= 100 km, configurable: magnitudes.$name.minDepth, magnitudes.$name.maxDepth

Note

The bindings configuration parameters magnitudes.Ms_20.lowerPeriod and magnitudes.Ms_20.upperPeriod are obsolete, not considered anymore and replace by magnitudes.$name.minPeriod and magnitudes.$name.maxPeriod, respectively.

Network magnitude

The network magnitude is computed from station magnitudes automatically by scmag or interactively by scolv. The trimmed mean method is applied. Outliers beyond the outer 12.5% percentiles are removed before forming the mean. The method can be adjusted in scmag by magnitudes.average.

Setup

1. Add and configure Ms_20-named amplitude and magnitude profiles in global bindings.

2. Add Ms_20 to the list of measured amplitudes and computed magnitudes in the module configuration of scamp, scmag and scolv.

3. Configure the averaging method in scmag.

4. Configure the magnitude priority list in scevent in case you wish to give priority to Ms_20 for becoming the preferred magnitude of an event.

5. Add Ms_20 the the list visible magnitudes in the module configuration of scesv or scolv. The magnitude will become visible in the summary view of the GUIs.