Tutorials¶
Creating the StDb Database¶
All the scripts provided require a StDb database containing station
information and metadata. Let’s first create this database for station
LOBS3 and send the prompt to a logfile
$ query_fdsn_stdb.py -N YH -C ?H? -S LOBS3 YH_list > logfile
To check the station info for M08A, use the program ls_stdb.py:
$ ls_stdb.py YH_list.pkl
Listing Station Pickle: YH_list.pkl
YH.LOBS3
--------------------------------------------------------------------------
1) YH.LOBS3
Station: YH LOBS3
Alternate Networks: None
Channel: HH ; Location: --
Lon, Lat, Elev: -38.79220, 179.14729, -3.540
StartTime: 2014-05-15 00:00:00
EndTime: 2015-06-23 23:59:59
Status: open
Polarity: 1
Azimuth Correction: 0.000000
BNG analysis¶
1. Automated analysis¶
We wish to use the entire deployment time of station LOBS3 to calculate the
station orientation using teleseismic P-wave data. Since the file YH_list.pkl
contains only one station, it is not necessary to specify a
key. This option would be useful if the database contained several stations
and we were only interested in downloading data for LOBS3. In this case, we would
specify --keys=LOBS3 or --keys=YH.LOBS3. We could use all the default
paramaters to do automated processing for regional events.
However, since we wish to analyze teleseismic data, we will edit a few of them to
include more waveform data around the predicted P-wave
arrival time. We also consider all earthquakes between 30 and 175 degrees, as the
program will automatically use either the P or PP waves to extract the waveforms.
The parameters to edit in this case are:
--times=-5.,15. to extract data from -5 to 15 seconds following P-wave arrival;
--window=60. to include 60 seconds of data;
--minmax=6. to limit the number of events to consider;
--mindist=30. for the minimum epicentral distance for teleseismic P; and
--bp=0.04,0.1 to focus on the long-period P waves
$ bng_calc_auto --times=-5.,15. --window=60. --bp=0.04,0.1 --min-mag=6. --min-dist=30. YH_list.pkl
An example log printed on the terminal will look like:
|==============================================|
| LOBS3 |
|==============================================|
| Station: YH.LOBS3 |
| Channel: HH; Locations: -- |
| Lon: 179.15; Lat: -38.79 |
| Start time: 2014-05-15 00:00:00 |
| End time: 2015-06-23 23:59:59 |
| Output Directory: BNG_RESULTS
| Save Progress: True
|----------------------------------------------|
| Searching Possible events: |
| Start: 2014-05-15 00:00:00 |
| End: 2015-06-23 23:59:59 |
| Mag: >6.0 |
| Min Distance: 30.0
| Max Distance: 175.0
| Max Depth: 1000.0
| Request Event Catalogue... |
| ... |
| Retrieved 178 events
**************************************************
* (1/178): 20150623_121830 YH.LOBS3
* Phase: P
* Origin Time: 2015-06-23 12:18:30
* Lat: 27.69; Lon: 139.79
* Dep: 472.30 km; Mag: 6.5
* Dist: 8420.96 km; Epi dist: 75.73 deg
* Baz: 324.49 deg; Az: 149.23 deg
* Requesting Waveforms:
* Startime: 2015-06-23 12:28:26
* Endtime: 2015-06-23 12:30:26
* LOBS3.HH - ZNE:
* HH[ZNE].-- - Checking Network
* HH[Z12].-- - Checking Network
* Stream has less than 3 components
* Error retrieving waveforms
**************************************************
**************************************************
* (3/178): 20150620_021007 YH.LOBS3
* Phase: P
* Origin Time: 2015-06-20 02:10:07
* Lat: -36.33; Lon: -73.67
* Dep: 17.40 km; Mag: 6.4
* Dist: 8837.94 km; Epi dist: 79.48 deg
* Baz: 128.47 deg; Az: 229.25 deg
* Requesting Waveforms:
* Startime: 2015-06-20 02:21:13
* Endtime: 2015-06-20 02:23:13
* LOBS3.HH - ZNE:
* HH[ZNE].-- - Checking Network
* HH[Z12].-- - Checking Network
* - Z12 Data Downloaded
* Start times are not all close to true start:
* HH1 2015-06-20T02:21:13.169200Z 2015-06-20T02:23:13.159182Z
* HH2 2015-06-20T02:21:13.170000Z 2015-06-20T02:23:13.159982Z
* HHZ 2015-06-20T02:21:13.171300Z 2015-06-20T02:23:13.161282Z
* True start: 2015-06-20T02:21:13.169017Z
* -> Shifting traces to true start
* Sampling rate is not an integer value: 100.00001525878906
* -> Resampling
* Waveforms Retrieved...
* PHI: 130.9734219019316
* SNR: 15.56466980049146
* CC: -0.5339708571207897
* 1-T/R: 0.6621867327600115
* 1-R/Z: -2.0528273045414216
...
And so on until all waveforms have been downloaded and processed. You will
notice that a folder called BNG_RESULTS/YH.LOBS3/ has been created.
This is where all processed files will be stored on disk.
2. Averaging¶
Now that all events have been processed, we wish to produce an average value of station orientation. However, not all estimates have equal weight in the final average. In particular, Braunmiller et al. (2020) have shown how a combination of parameters can be used to exclude poorly constrained estimates to produce a more robust final estimate. Here we will use all default values in the script and specify arguments to plot and save final figures.
$ bng_average --plot --save YH_list.pkl
An example log printed on the terminal will look like:
|==============================================|
| LOBS3 |
|==============================================|
| Station: YH.LOBS3 |
| Channel: HH; Locations: -- |
| Lon: 179.15; Lat: -38.79 |
| Input Directory: BNG_RESULTS
| Plot Results: True
|
| B-N-G mean, error, data included: 118.44, 7.49, 16
The first figure to pop up will show the various combinations of quality factors, highlighting the estimates that pass the selected (default) thresholds
The second figure displays the estimates according to three parameters:
Signal-to-noise ratio (SNR)
Cross-correlation coefficient (CC)
Earthquake magnitude
DL analysis¶
1. Automated analysis¶
We wish to use the entire deployment time of station LOBS3 to calculate the
station orientation using Rayleigh-wave polarization data. Following the previous
example, since the file YH_list.pkl contains only one station, it is not
necessary to specify a key. Here we use all default parameters, except for the
minimum earthquake magnitude, which we set to 6.
$ dl_calc --min-mag=6. YH_list.pkl
An example log printed on the terminal will look like:
Establishing Catalogue Client...
Done
Establishing Waveform Client...
Done
|==============================================|
| LOBS3 |
|==============================================|
| Station: YH.LOBS3 |
| Channel: HH; Locations: -- |
| Lon: 179.15; Lat: -38.79 |
| Start time: 2014-05-15 00:00:00 |
| End time: 2015-06-23 23:59:59 |
| Output Directory: DL_RESULTS
| Save Progress: True
|----------------------------------------------|
| Searching Possible events: |
| Start: 2014-05-15 00:00:00 |
| End: 2015-06-23 23:59:59 |
| Mag: >{0:3.1f} 6.0 |
| Min Distance: 5.0
| Max Distance: 175.0
| Max Depth: 150.0
| Request Event Catalogue... |
| ... |
| Retrieved 178 events
**************************************************
* (3/178): 20150620_021007 YH.LOBS3
* Origin Time: 2015-06-20 02:10:07
* Lat: -36.33; Lon: -73.67
* Dep: 17.40 km; Mag: 6.4
* Dist: 8837.94 km; Epi dist: 79.48 deg
* Baz: 128.47 deg; Az: 229.25 deg
* Requesting Waveforms:
* Startime: 2015-06-20 02:10:07
* Endtime: 2015-06-20 06:10:07
* LOBS3.HH - ZNE:
* HH[ZNE].-- - Checking Network
* HH[Z12].-- - Checking Network
* - Z12 Data Downloaded
* Start times are not all close to true start:
* HH1 2015-06-20T02:10:07.650900Z 2015-06-20T06:10:07.638703Z
* HH2 2015-06-20T02:10:07.651100Z 2015-06-20T06:10:07.638903Z
* HHZ 2015-06-20T02:10:07.659300Z 2015-06-20T06:10:07.637103Z
* True start: 2015-06-20T02:10:07.650000Z
* -> Shifting traces to true start
* Sampling rate is not an integer value: 100.00001525878906
* -> Resampling
* Waveforms Retrieved...
* R1PHI: [ 108.2734219 117.2734219 125.0734219 126.8734219 112.5734219
101.3734219 121.3734219]
* R2PHI: [ 120.3734219 114.6734219 114.8734219 9.3734219 4.4734219
319.2734219 88.3734219]
* R1CC: [ 0.3929253 0.63498115 0.79618113 0.76866093 0.52087365 0.28555018
0.27791771]
* R2CC: [ 0.27178087 0.07950989 0.16644224 0.51027084 0.24789322 0.04376891
0.03245475]
...
And so on until all waveforms have been downloaded and processed. You will
notice that a folder called DL_RESULTS/YH.LOBS3/ has been created.
This is where all processed files will be stored on disk.
2. Averaging¶
Now that all events have been processed, we wish to produce an average value of station orientation. However, not all estimates have equal weight in the final average. In particular, Doran and Laske have shown how to specify a threshold cross-correlation (CC) value to exclude waveforms for which the CC between the radial and Hilbert-transformed vertical component is low. Here we use the default CC threshold of 0.8 and produce a final plot with the estimate.
$ dl_average --plot YH_list.pkl
An example log printed on the terminal will look like:
|==============================================|
| LOBS3 |
|==============================================|
| Station: YH.LOBS3 |
| Channel: HH; Locations: -- |
| Lon: 179.15; Lat: -38.79 |
| Input Directory: DL_RESULTS
| Plot Results: True
|
| D-L mean, error, data included: 122.95, 3.99, 284
| D-L CC level: 0.8
The figure displays the estimates according to the CC value:
