seisflows.tools.signal

Signal processing or manipulation functions which are used to manipulate time series, or interact with ObsPy Trace and Stream objects. Primarily used by the Preprocessing module

Functions

filter(st, choice[, min_freq, max_freq, zerophase])

Apply a filter to waveform data using ObsPy, throw on a standard

trim(st, st_trim)

Trims the time waveform of st_trim to match the time series of st. This

resample(st_a, st_b)

Resample all traces in st_a to the sampling rate of st_b. Resamples

normalize(st[, choice, st_rel])

Normalize amplitudes of Stream object waveforms based on the given choice of

mute(st)

Apply mute on data based on early or late arrivals, and short or long

mask(slope, const, offset, nt, dt[, length])

Constructs a tapered mask that can be applied to trace to mute early or

mute_arrivals(st, slope, const, choice)

Apply a tapered mask to a set of waveforms in a Stream to mute early or

mute_offsets(st, dist, choice)

Mute traces based on a given distance (dist)

get_receiver_coords(st)

Retrieve the coordinates from a Stream object.

get_source_coords(st)

Get the coordinates of the source object.

Module Contents

seisflows.tools.signal.filter(st, choice, min_freq=None, max_freq=None, zerophase=True, **kwargs)

Apply a filter to waveform data using ObsPy, throw on a standard demean, detrened and taper prior to filtering. Options for different filtering types. Uses default filter options from ObsPy.

Zerophase enforced to be True to avoid phase shifting data.

Parameters:

st (obspy.core.stream.Stream) – stream to be filtered

Return type:

obspy.core.stream.Stream

Returns:

filtered traces

seisflows.tools.signal.trim(st, st_trim)

Trims the time waveform of st_trim to match the time series of st. This allows cutting down longer observed waveform data so that preprocessing steps are not performed on unncessarily long time series.

Parameters:

  • st (obspy.core.stream.Stream) – Stream that sets the desired time series

  • st_trim (obspy.core.stream.Stream) – Stream that will have its time series cut to match st

Return type:

(obspy.core.stream.Stream, obspy.core.stream.Stream)

Returns:

(st, trimmed version of st_trim)

seisflows.tools.signal.resample(st_a, st_b)

Resample all traces in st_a to the sampling rate of st_b. Resamples one to one, that is each trace in obs is resampled to the corresponding indexed trace in syn

Parameters:

  • st_a (obspy.core.stream.Stream) – stream to be resampled using sampling rates from st_b

  • st_b (obspy.core.stream.Stream) – stream whose sampling rates will be used to resample st_a. Usually this is the synthetic data

Return type:

(obspy.core.stream.Stream, obspy.core.stream.Stream)

Returns:

st_a (resampled), st_b (original)

seisflows.tools.signal.normalize(st, choice=None, st_rel=None)

Normalize amplitudes of Stream object waveforms based on the given choice of normalization function.

Parameters:

  • st (obspy.core.stream.Stream) – All of the data streams to be normalized

  • choice (str) – choice of normalization parameter, from the following: - None: Do not normalize. Used to bypass procedure TRACE-WISE NORMALIZATION - TNORML1: normalize per trace by the L1 norm of itself - TNORML2: normalize per trace by the L2 norm of itself - TNORM_MAX: normalize by the maximum positive amplitude in the trace - TNORM_ABSMAX: normalize by the absolute maximum amplitude in the trace - TNORM_MEAN: normalize by the mean of the absolute trace RELATIVE NORMALIZATION - RNORM_MAX: normalize st by the max positive amplitude of st_rel - RNORM_ABSMAX: normalize st by abs max amplitude of st_rel

  • st_rel (obspy.core.stream.Stream) – Second stream used for relative normalization. Optional and only required if ‘RNORM’ set as choice

Return type:

obspy.core.stream.Stream

Returns:

stream with normalized traces

seisflows.tools.signal.mute(st)

Apply mute on data based on early or late arrivals, and short or long source receiver distances

Parameters:

st (obspy.core.stream.Stream) – stream to mute

Return type:

obspy.core.stream.Stream

Returns:

muted stream object

seisflows.tools.signal.mask(slope, const, offset, nt, dt, length=400)

Constructs a tapered mask that can be applied to trace to mute early or late arrivals. Called by the Default preprocessing module.

Note

t_mask = slope * offset + const itmin = t_mask - length/2 itmax = t_mask + length/2 t_array = [itmin, itmax]

offset = || s - r || is distance between source and receiver [m] const has units of time [s] slope has units of time/dist (or velocity**-1) [s/m]

Parameters:

  • slope (float) – slope applied to source receiver distance to mute arrivals

  • const (float) – a constant time offset used to shift the mask in time

  • offset (float) – source-receiver distance in units of distance

  • nt (int) – number of samples in the waveform to be masked

  • dt (float) – sampling rate of the waveform to be masked

  • length (int) – length, in time of the output mask function

Return type:

np.array

Returns:

A mask array that can be directly multipled with a waveform

seisflows.tools.signal.mute_arrivals(st, slope, const, choice)

Apply a tapered mask to a set of waveforms in a Stream to mute early or late arrivals

Parameters:

  • st (obspy.stream) – Stream object containing waveforms to mute

  • slope (float) – slope applied to source receiver distance to mute arrivals

  • const (float) – a constant time offset used to shift the mask in time

  • choice (str) – “early” to mute early arrivals, “late” to mute late arrivals

Return type:

obspy.stream

Returns:

muted stream object

seisflows.tools.signal.mute_offsets(st, dist, choice)

Mute traces based on a given distance (dist)

short: ||s-r|| < dist long: ||s-r|| > dist

Parameters:

  • st (obspy.stream) – Stream object containing waveforms to mute

  • dist (float) – cutoff distancekil

  • choice (str) – “short” to mute short src-rcv distances, “long” to mute long src-rcv distances

Return type:

obspy.stream

Returns:

muted stream object

seisflows.tools.signal.get_receiver_coords(st)

Retrieve the coordinates from a Stream object. Only works for SU format currently

Parameters:

st (obspy.core.stream.Stream) – a stream to query for coordinates

Rtype r_coords:

list

Return r_coords:

list of receiver coordinates, matching the order in st ([rx], [ry], [rz])

seisflows.tools.signal.get_source_coords(st)

Get the coordinates of the source object. Only works for SU format currently

Parameters:

st (obspy.core.stream.Stream) – a stream to query for coordinates

Rtype s_coords:

tuple of lists

Return s_coords:

list of source coordinates, matching the order in st ([sx], [sy], [sz])