2. Single earthquake example (for multiple receiver observations)
Example of shear-wave splitting applied to an icequake from Rutford Ice Stream, Antarctica.
The event is an icequake from Hudson et al. (2020).
Hudson, T.S., Brisbourne, A.M., Walter, F., Graff, D., & White, R. S. (2020). Icequake source mechanisms for studying glacial sliding. Journal of Geophysical Research: Earth Surface. https://doi.org/10.1029/2020JF005627
[1]:
%load_ext autoreload
%autoreload 2
[2]:
import swspy
import obspy
from obspy import UTCDateTime
import numpy as np
%matplotlib notebook
import matplotlib.pyplot as plt
%matplotlib notebook
2.1. 1. Load data for event:
Data can be from an archive of continuous seismic data, or from a mseed file containing only data for the event.
[3]:
# Load data:
archive_vs_file = "file"
mseed_file_path = "data/20090121042009180_ice_flow_dir_corrected.m"
nonlinloc_event_path = "data/loc.Tom__RunNLLoc000.20090121.042009.grid0.loc.hyp"
starttime = UTCDateTime("20090121T042009.18523") - 0.5
endtime = UTCDateTime("20090121T042009.18523") + 2.5
load_wfs_obj = swspy.io.load_waveforms(mseed_file_path, starttime=starttime, endtime=endtime, archive_vs_file=archive_vs_file)
load_wfs_obj.filter = True
load_wfs_obj.filter_freq_min_max = [1.0, 80.0]
st = load_wfs_obj.read_waveform_data()
2.2. 2. Calculate splitting:
Note: Here, event information such as S arrival time, ray back-azimuth and ray inclination are taken automatically from a nonlinloc event file (see other examples for manual passing of these parameters).
[4]:
# Calculate splitting:
splitting_event = swspy.splitting.create_splitting_object(st, nonlinloc_event_path=nonlinloc_event_path) #(st, nonlinloc_event_path) #(st.select(station="ST01"), nonlinloc_event_path)
splitting_event.overall_win_start_pre_fast_S_pick = 0.3
splitting_event.win_S_pick_tolerance = 0.1
splitting_event.overall_win_start_post_fast_S_pick = 0.2
splitting_event.rotate_step_deg = 2.0
splitting_event.max_t_shift_s = 0.1
splitting_event.n_win = 10
splitting_event.perform_sws_analysis(coord_system="ZNE", sws_method="EV")
No S phase pick for station: ST08 therefore skipping this station.
No S phase pick for station: ST06 therefore skipping this station.
No S phase pick for station: ST10 therefore skipping this station.
No S phase pick for station: ST09 therefore skipping this station.
No S phase pick for station: ST07 therefore skipping this station.
[4]:
| station | phi_from_Q | phi_from_N | phi_from_U | phi_err | dt | dt_err | src_pol_from_N | src_pol_from_U | src_pol_from_N_err | src_pol_from_U_err | Q_w | lambda2/lambda1 ratio | ray_back_azi | ray_inc | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | ST05 | 26.0 | 74.57 | 90.0 | 11.0 | 0.004 | 0.003 | 154.197600 | 89.946359 | 17.214782 | 10.537896 | NaN | 0.055499 | 48.57 | 141.8 |
| 0 | ST04 | -48.0 | 54.07 | 90.0 | 3.0 | 0.044 | 0.001 | 165.368197 | 90.444536 | 6.430684 | 3.923207 | NaN | 0.033150 | 282.07 | 163.9 |
| 0 | ST02 | 38.0 | 67.53 | 90.0 | 3.0 | 0.042 | 0.018 | 163.575889 | 90.504097 | 6.436617 | 2.740569 | NaN | 0.034949 | 29.53 | 160.6 |
| 0 | ST03 | -82.0 | -87.53 | 90.0 | 6.0 | 0.020 | 0.001 | 26.199288 | 95.881281 | 12.880766 | 23.807806 | NaN | 0.068566 | 354.47 | 144.4 |
| 0 | ST01 | -60.0 | 48.74 | 90.0 | 5.0 | 0.048 | 0.002 | 168.369942 | 88.213619 | 9.483751 | 6.103969 | NaN | 0.052323 | 108.74 | 156.5 |
2.3. 3. Plot result:
[5]:
splitting_event.plot(outdir='plots')
/Users/eart0504/Documents/python/github_repositories/swspy/swspy/splitting/split.py:1907: UserWarning: constrained_layout not applied. At least one axes collapsed to zero width or height.
plt.savefig(os.path.join(outdir, ''.join((self.event_uid, "_", station, ".png"))), dpi=300)
/Users/eart0504/Documents/python/github_repositories/swspy/swspy/splitting/split.py:1907: UserWarning: constrained_layout not applied. At least one axes collapsed to zero width or height.
plt.savefig(os.path.join(outdir, ''.join((self.event_uid, "_", station, ".png"))), dpi=300)
No S phase pick for station: ST08 therefore skipping this station.
Skipping waveform correction for station: ST08
No S phase pick for station: ST06 therefore skipping this station.
Skipping waveform correction for station: ST06
No S phase pick for station: ST10 therefore skipping this station.
Skipping waveform correction for station: ST10
/Users/eart0504/Documents/python/github_repositories/swspy/swspy/splitting/split.py:1907: UserWarning: constrained_layout not applied. At least one axes collapsed to zero width or height.
plt.savefig(os.path.join(outdir, ''.join((self.event_uid, "_", station, ".png"))), dpi=300)
/Users/eart0504/Documents/python/github_repositories/swspy/swspy/splitting/split.py:1907: UserWarning: constrained_layout not applied. At least one axes collapsed to zero width or height.
plt.savefig(os.path.join(outdir, ''.join((self.event_uid, "_", station, ".png"))), dpi=300)
/Users/eart0504/Documents/python/github_repositories/swspy/swspy/splitting/split.py:1907: UserWarning: constrained_layout not applied. At least one axes collapsed to zero width or height.
plt.savefig(os.path.join(outdir, ''.join((self.event_uid, "_", station, ".png"))), dpi=300)
No S phase pick for station: ST09 therefore skipping this station.
Skipping waveform correction for station: ST09
No S phase pick for station: ST07 therefore skipping this station.
Skipping waveform correction for station: ST07
2.4. 4. Save result:
[6]:
# And save result to file:
splitting_event.save_result()
Saved sws result to: /Users/eart0504/Documents/python/github_repositories/swspy/docs/source/tutorials/single_event_example/20090121042009_sws_result.csv
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