Data Processing

demean!(S::SeisData[; chans=CC, irr=false])

Remove the mean from all channels i with S.fs[i] > 0.0. Specify irr=true to also remove the mean from irregularly sampled channels (with S.fs[i] == 0.0). Specifying a channel list with chans=CC restricts processing to channels CC.

demean!(C::SeisChannel)

Remove the mean from data in C.

Ignores NaNs.

detrend!(S::SeisData[; chans=CC, n=1]))

Remove the linear trend from channels CC. Ignores NaNs.

To remove a higher-order polynomial fit than a linear trend, choose n >1.

detrend!(C::SeisChanel[; n=1]))

Remove the linear trend from data in C. Ignores NaNs.

To remove a higher-order polynomial fit than a linear trend, choose n>1.

env!(S::GphysData[, chans=CC, v=V])
env(S::GphysData)

Compute the envelope of channel data in S. Only affects regularly-sampled channels.

In-place conversion of S.x[i] ==> Env(S.x[i]) (≡ |H(S.x[i])|, where H denotes the Hilbert transform).

Keywords

• chans=CC: only process channels in CC (with fs > 0.0).
• v=V: verbosity.

nanfill!(S::SeisData)
nanfill!(C::SeisChannel)

For each channel i in S, replace all NaNs in S.x[i] with the mean of non-NaN values.

resample!(S::SeisData [, chans=CC, fs=FS])
resample(S::SeisData [, chans=CC, fs=FS])

Resample data in S to FS. If keyword fs is not specified, data are resampled to the lowest non-zero value in S.fs[CC].Note that a poor choice of FS can lead to upsampling and other undesirable behavior.

Use keyword chans=CC to only resample channel numbers CC. By default, all channels i with S.fs[i] > 0.0 are resampled.

resample!(C::SeisChannel, fs::Float64)
resample(C::SeisChannel, fs::Float64)

Resample C.x to fs.

unscale!(S::GphysData[, chans=CC, irr=false])

Divide out the gains of all channels i where S.fs[i] > 0.0. Specify irr=true to also remove the gains of irregularly-sampled channels. Use keyword chans=CC to only resample channel numbers CC.

convert_seis!(S[, chans=CC, units_out=UU, v=V])
convert_seis(S, chans=CC, units_out=UU, v=V])
convert_seis!(C[, units_out=UU, v=V])
convert_seis(CC, units_out=UU, v=V)

Convert all seismic data channels in S to velocity seismograms, differentiating or integrating as needed.

Keywords

• units_out=UU specifies output units.
  • Default: "m/s".
  • Allowed: "m", "m/s", or "m/s2". (SeisBase uses Unicode (UTF-8) UCUM units.)
• v=V sets verbosity.
• chans=CC restricts seismogram conversion to seismic data channels within CC.
  • chans can be an Integer, UnitRange, or Array{Int64,1}.
  • By default, all seismic data channels in S are converted (if needed).
  • This does not allow convert_seis! to work on non-seismic data.

References

1. Neumaier, A. (1974). "Rundungsfehleranalyse einiger Verfahren zur Summation endlicher Summen" [Rounding Error Analysis of Some Methods for Summing Finite Sums]. Zeitschrift für Angewandte Mathematik und Mechanik (in German). 54 (1): 39-51. doi:10.1002/zamm.19740540106.

ungap!(S[, chans=CC, m=true, tap=false])
ungap(S[, chans=CC, m=true, tap=false])

Fill time gaps in each channel of S with the mean of the channel data.

ungap!(C[, m=true, tap=false])
ungap(C[, m=true, tap=false])

As above for GphysChannel object C.

Keywords

• chans=CC: only ungap channels CC.
• m=false: this flag fills gaps with NaNs instead of the mean.
• tap=true: taper data before filling gaps.

merge!(S::SeisData, U::SeisData[, prune_only=true])

Merge channels of two SeisData structures.

Merge two GphysData structures. For timeseries data, a single-pass merge-and-prune operation is applied to value pairs whose sample times are separated by less than half the sampling interval.

merge!(S::SeisData[, prune_only=true])

"Flatten" a SeisData structure by merging channels with identical properties.

If prune_only=true, the only action taken is deletion of empty and duplicate channels; merge!(S, U, prune_only=true) is identical to an in-place S+U.

mseis!(S::SeisData, U...)

Merge multiple SeisData structures at once. The first argument (merge target) must be a SeisData structure. Subsequent structures can be any type T <: Union{GphysData, GphysChannel, SeisEvent}.

mseis!(C::GphysChannel, U...)

Merge all channels in U that match channel C into object C. To be merged, a channel must match on fields :id, :fs, :loc, :resp, :units.

See also: merge!

translate_resp!(S, resp_new[, chans=CC, wl=γ])
translate_resp(S, resp_new[, chans=CC, wl=γ])

Translate the instrument response of seismic data channels CC in S to resp_new. Replaces field :resp with resp_new for all affected channels.

remove_resp!(S, chans=CC, wl=γ])
remove_resp(S, chans=CC, wl=γ])

Remove (flatten to DC) the instrument response of seismic data channels cha in S. Replaces field :resp with the appropriate (all-pass) response.

translate_resp!(Ch, resp_new[, wl=γ])
translate_resp(Ch, resp_new[, wl=γ])

Translate the instrument response of seismic data in SeisChannel object Ch to resp_new. Replaces field :resp with resp_new.

remove_resp!(Ch[, chans=CC, wl=γ])
remove_resp(Ch[, chans=CC, wl=γ])

Remove (flatten to DC) the instrument response of seismic data in Ch. Replaces field :resp with the appropriate (all-pass) response.

Keywords

• chans=CC restricts response translation to channel(s) CC. By default, all seismic data channels have responses translated to resp_new.
• wl=γ sets the waterlevel to γ (default: γ = eps(Float32) ≈ ~1f-7)

The waterlevel is the minimum magnitude (absolute value) of the normalized old frequency response; in other words, if the old frequency response has a maximum magnitude of 1.0, then no response coefficient can be lower than g. This is useful to prevent "divide by zero" errors, but setting it too high will cause errors.

Interaction with the :resp field

translate_resp and remove_resp only work on a channel i that satisfies S.resp[i] <: PZResp, PZResp64, MultiStageResp. In the last case, S.resp[i].stage[1] must be a PZResp or PZResp64, only the first stage of the response is changed, and the stage gain is ignored; instead, the sensitivity S.resp[i].stage[1].a0 is used.

Poles and zeros should be rad/s

Always check when loading from an unsupported data format. Responses read from station XML are corrected to rad/s automatically (most use rad/s); responses read from a SACPZ or SEED RESP file already use rad/s.

sync!(S::GphysData)

Synchronize the start times of all data in S to begin at or after the last start time in S.

sync!(S[, s=TS, t=TT, pad=false, v=V])

Synchronize all data in S to start no earlier than TS and terminate no later than TT, with verbosity level V.

By default, a channel with mean μᵢ = mean(S.x[i]) that begins after TS is prepended with μᵢ to begin exactly at TS; similarly, if keyword t is used, μᵢ is appended so that data ends at TT. If pad=false, channels that begin after TS or end before TT are not extended in either direction.

For regularly-sampled channels, gaps between the specified and true times are filled with the mean; this isn't possible with irregularly-sampled data.

Specifying start time (s=)

• s="last": (Default) sync to the last start time of any channel in S.
• s="first": sync to the first start time of any channel in S.
• A numeric value is treated as an epoch time (?time for details).
• A DateTime is treated as a DateTime. (see Dates.DateTime for details.)
• Any string other than "last" or "first" is parsed as a DateTime.

Specifying end time (t=)

• t="none": (Default) end times are not synchronized.
• t="last": synchronize all channels to end at the last end time in S.
• t="first" synchronize to the first end time in S.
• numeric, datetime, and non-reserved strings are treated as for s=.

See also: TimeSpec, Dates.DateTime, parsetimewin

taper!(C[; t_max::Real=10.0, α::Real=0.05, N_min::Int64=10])

Cosine taper all time-series data in C. Tapers each segment of each channel that contains at least N_min total samples.

taper!(S[; chans=CC, t_max::Real=10.0, α::Real=0.05, N_min::Int64=10])

Cosine taper each segment of time-series data in GphysChannel object C that contains at least N_min total samples.

Does not modify irregularly-sampled data channels.

Keywords:

• chans: Only taper the specified channels.
• N_min: Data segments with N < N_min total samples are not tapered.
• t_max: Maximum taper edge in seconds.
• α: Taper edge area; as for a Tukey window, the first and last 100*α% of

samples in each window are tapered, up to t_max seconds of data.

See also: DSP.Windows.tukey

filtfilt!(S::GphysData[; KWs])

Apply zero-phase filter to S.x.

filtfilt!(C::GphysChannel[; KWs])

Apply zero-phase filter to C.x

Keywords control filtering behavior; specify as e.g. filtfilt!(S, fl=0.1, np=2, rt="Lowpass").

Keywords

1. Allowed types are Integer, UnitRange, and Array{Int64, 1}.
2. By convention, the lower corner frequency (fl) is used in a Highpass

filter, and fh is used in a Lowpass filter.

Default filtering KW values can be changed by adjusting the Shared Keywords, e.g., SeisBase.KW.Filt.np = 2 changes the default number of poles to 2.

See also: DSP.jl documentation