Surface wave magnitude measured at around 20 s
Ms_20 is the surface wave magnitude measured on the vertical component at around 20 s period in accordance with the IASPEI standards.
The Ms_20 amplitudes are calculated on vertical-component displacement seismograms corrected for the instrument response of a WWSSN_LP seismograph.
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 (:cite:t:`iaspei-2013`).
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 (:cite:t:`iaspei-2013`). Alternatively, the term Ms(20) may be used.
Amplitude unit in SeisComP: nanometer (nm)
Time window: 0 s - distance (km) / 3.5 km/s + 30 s
Depth range: <= 100 km, configurable:
By default, the trimmed mean is calculated from the station magnitudes to form the network magnitude. Outliers below the 12.5% and above the 12.5% percentiles are removed before the calculation.