next up previous contents index
Next: 21.3 AUTOSIG Up: 21. Automatic routines in Previous: 21.1 AUTOPIC and AUTO   Contents   Index


21.2 AUTOPHASE, automatic phase picking

By T. Utheim terje.utheim@geo.uib.no

The AUTOPHASE program is part of the RTQUAKE real-time earthquake detection [Utheim et al., 2014] (Utheim and Havskov, 2014). The AUTOPHASE (hereafter AP) is a stand-alone phase-picker routine that is used for automatic phase-picking in RTQUAKE and can also be used as an option in SEISAN from the EEV program. The routine is based on the FilterPicker algorithm [A. Lomax and Vassallo, 2012] (Lomax et al. 2012), but with several modifications and additions. However, the original picking algorithm is unchanged.

The FilterPicker (hereafter FP) implementation in both RTQUAKE and SEISAN checks each component of a waveform for possible phase-picks. All channels in the waveform file are checked and there is no possibility to unselect channels. Each component may have several suggested phases given by the time of occurrence. Each component may also have a suggested first movement indicated for each pick. There can thus be many picks for each channel.

The following rules apply for selecting P and S phases among the suggested picks:

For one station there will only be one P and one S-phase selected.

P is only accepted on vertical components.

S is only accepted on vertical components if the station does not have horizontal components so S is in general only accepted on horizontal components. If several picks are found on a horizontal component, it is assumed that the first is P. The S is then selected on the first of the following picks that has a time-difference greater than a default value MINDIFF (1.5 seconds) set in the program. This is to avoid picking secondary P phases as S phases. This rule is also used if picking S on Z-components.

If S-phases are found on two different horizontal channels, the first arriving one is used.

If only one pick on a horizontal component, no S is selected.

First movement are included in the S-file only for vertical channels.

If the event is defined as distant (D) in the SEISAN S-file, only P phases are picked.

S-phases are given a weight of 3.

Running AUTOPHASE AP is started from within the SEISAN EEV program with the command 'ap'. This command converts all associated waveform files (can be different formats) to one MiniSeed file seed.out, which is then used as input to AUTOPHASE. The S-file and corresponding waveform files are used as input to the AP. All old readings are deleted and replaced by the new readings from AP. All phases are marked with A for automatic. AUTOPHASE can also be operated outside EEV with the command:

Autophase -sfile xxx -wavefile yyy

where xxx is a single event S-file and yyy is one waveform file in MiniSeed format. AP can only work with one S-file.

AUTOPHASE also has other options not used in SEISAN, see RTQUAKE manual (ftp://ftp.geo.uib.no/pub/seismo/SOFTWARE/RTQUAKE/).

Parameters

AUTOPHASE has no parameter file since it seems that the default parameter work will in most cases. Default FilterPicker parameters are set at the top in the source program under the comment:

"Default FilterPicker parameters" and can be changed by the user. See M. Vassallo and Lomax [2012] Vassallo et al. (2012) for documentation. The program must be recompiled.

#define Picker_FW 300.0 Longest period for a set of filtered signals from the differential signal of the raw broadband input trace (300 multiplied by sample rate)

#define Picker_LTW 500.0 Time scale used for accumulating time-averaged statistics of the input raw signal (500 multiplied by sample rate)

#define Picker_TH1 10.0 Trigger threshold used for event declaration. A trigger is declared when the summary CF (characteristic function) exceeds Picker_TH1

#define Picker_TH2 10.0 A pick is declared if and when, within a window of predefined time width, Picker_TUP after trigger time, the integral summary CF (characteristic function) exceeds the value: Picker_TH2 multiplied by Picker_TUP (see below).

#define Picker_TUP 20.0 Time window used for pick validation (20 multiplied by sample rate).

Default time-difference MINDEF is set to:

MINDEF = 1.5

Coda is computed for vertical components only, and only for events marked local (L) or regional (R) in the s-file. Computation of coda can be turned off by changing the SETCODA switch in the source code to zero, and recompiling. Default is SETCODA=1. The coda is computed by comparing a long-term average of the signal before the P phase with long-term averages after the P-phase divided by a factor.

Figure 21.1: Examples of automatic picks on a "good" event.
\begin{figure}\centerline{\includegraphics[width=0.9\linewidth]{fig/autophase}}\end{figure}

Example: The AUTOPHASE picker is started from EEV with the command: ap


#   13  9 Dec 2015 08:03 54  LM-22.259 -66.832  0.0  N 1.2 2.3WBER   11  ? ap
The waveform file is converted to miniseed file: seed.out
wavetool -sfile /home/seismo/snew/REA/TST__/2015/12/09-0804-18R.S201512 -format MSEED -wav_out_file seed.out                                                                                                                                                                                                                                                                                                    
  Number of wav-files           1
  Number of wav-files present           1
 /home/seismo/snew/WAV/TST__/2015/12/2015  MINISEED  
  Total number of channels available:          42
  Total duration:   323.599976    

  Output waveform file name is seed.out
Here the autophase routine is started with s-file and seed.out file as input:
autophase -sfile /home/seismo/snew/REA/TST__/2015/12/09-0804-18R.S201512 -wavefile seed.out                                                                                                                                                                                                                                                                                                                     
SEISAN_TOP.......................: /home/seismo/snew
wfilename: seed.out
All picks found are listed below in the format:
STATION-NAME      DATE      TIME       TIME-DIFFERENCE TO NEXT PICK ON SAME COMPONENT
CX_PB16__00_BHZ 09/12/15 08:05:04.499        (1 pick only)
CX_PB11__00_BHZ 09/12/15 08:04:49.150 39.85  (2 picks, time-diff. to 2. pick:39.85 seconds)
CX_PB11__00_BHN 09/12/15 08:04:49.349 39.30
CX_PB11__00_BHE 09/12/15 08:04:49.349 39.55
CX_PB08__00_BHZ 09/12/15 08:04:43.769
CX_PB08__00_BHN 09/12/15 08:04:43.819 35.35
CX_PB08__00_BHE 09/12/15 08:04:43.919 35.40
CX_PB01__00_BHZ 09/12/15 08:04:38.269
CX_PB01__00_BHN 09/12/15 08:04:38.569 31.25
CX_PB01__00_BHE 09/12/15 08:04:38.569 31.95
CX_PB07__00_BHZ 09/12/15 08:04:39.019
CX_PB07__00_BHN 09/12/15 08:04:38.969
CX_PB07__00_BHE 09/12/15 08:04:39.069
CX_PB09__00_BHZ 09/12/15 08:04:33.650
CX_PB09__00_BHN 09/12/15 08:04:33.999
CX_PB09__00_BHE 09/12/15 08:04:33.799
CX_PB03__00_BHZ 09/12/15 08:04:37.569
CX_PB03__00_BHN 09/12/15 08:04:37.469
CX_PB03__00_BHE 09/12/15 08:04:37.469
CX_PB04__00_BHZ 09/12/15 08:04:41.369
CX_PB04__00_BHN 09/12/15 08:04:41.669
CX_PB04__00_BHE 09/12/15 08:04:41.619  0.90
CX_PB06__00_BHZ 09/12/15 08:04:36.519
CX_PB06__00_BHN 09/12/15 08:04:36.919 30.15
CX_PB06__00_BHE 09/12/15 08:04:36.769
CX_PB05__00_BHZ 09/12/15 08:04:42.619
CX_PB05__00_BHN 09/12/15 08:04:43.069
CX_PB05__00_BHE 09/12/15 08:04:42.769
CX_PB15__00_BHZ 09/12/15 08:04:37.869  1.20 30.50 (3 picks,and 2 time-differences)
CX_PB15__00_BHN 09/12/15 08:04:37.669 31.65
CX_PB15__00_BHE 09/12/15 08:04:38.169 31.30
CX_PB10__00_BHE 09/12/15 08:04:48.500
-----------------------------------------------------------------------
SELECTED PICKS:
-----------------------------------------------------------------------
Below the selected picks from the picks above. As seen below, there are picks on both 
horizontal components on stations PB11,PB08,PB01 and PB15:
  0 PB16  BHZ   P 09/12/15 08:05:04.499                              
  6 PB11  BHZ   P 09/12/15 08:04:49.150                              
  7 PB11  BHN                              S 09/12/15 08:05:28.649
  8 PB11  BHE                              S 09/12/15 08:05:28.899
  9 PB08  BHZ   P 09/12/15 08:04:43.769 C                            
 10 PB08  BHN                              S 09/12/15 08:05:19.169
 11 PB08  BHE                              S 09/12/15 08:05:19.319
 12 PB01  BHZ   P 09/12/15 08:04:38.269                              
 13 PB01  BHN                              S 09/12/15 08:05:09.819
 14 PB01  BHE                              S 09/12/15 08:05:10.519
 15 PB07  BHZ   P 09/12/15 08:04:39.019                              
 18 PB09  BHZ   P 09/12/15 08:04:33.650 C                            
 21 PB03  BHZ   P 09/12/15 08:04:37.569                              
 24 PB04  BHZ   P 09/12/15 08:04:41.369                              
 27 PB06  BHZ   P 09/12/15 08:04:36.519                              
 28 PB06  BHN                              S 09/12/15 08:05:07.069
 30 PB05  BHZ   P 09/12/15 08:04:42.619                              
 33 PB15  BHZ   P 09/12/15 08:04:37.869                              
 34 PB15  BHN                              S 09/12/15 08:05:09.319
 35 PB15  BHE                              S 09/12/15 08:05:09.469
----------------------------------------------------------------------------------------
In the next step of selection the first of the 2 S-phases on the horizontal components 
are selected while the last are deleted:
  0 PB16  BHZ   P 09/12/15 08:05:04.499                              
  6 PB11  BHZ   P 09/12/15 08:04:49.150                              
  7 PB11  BHN                              S 09/12/15 08:05:28.649
  9 PB08  BHZ   P 09/12/15 08:04:43.769 C                            
 10 PB08  BHN                              S 09/12/15 08:05:19.169
 12 PB01  BHZ   P 09/12/15 08:04:38.269                              
 13 PB01  BHN                              S 09/12/15 08:05:09.819
 15 PB07  BHZ   P 09/12/15 08:04:39.019                              
 18 PB09  BHZ   P 09/12/15 08:04:33.650 C                            
 21 PB03  BHZ   P 09/12/15 08:04:37.569                              
 24 PB04  BHZ   P 09/12/15 08:04:41.369                              
 27 PB06  BHZ   P 09/12/15 08:04:36.519                              
 28 PB06  BHN                              S 09/12/15 08:05:07.069
 30 PB05  BHZ   P 09/12/15 08:04:42.619                              
 33 PB15  BHZ   P 09/12/15 08:04:37.869                              
 34 PB15  BHN                              S 09/12/15 08:05:09.319
-----------------------------------------------------------------------
Create s-file: /home/seismo/snew/REA/TST__/2015/12/09-0804-18R.S201512
-----------------------------------------------------------------------
The autophase routine will also indicate first movement of p-phases when found. This can 
be seen on station PB08 BZ and PB09 BZ below:
 0  2015 12 9 0803 54.7 LM-22.259 -66.832  0.0  BER 11 1.2 2.3WBER                1
 1  SPEC AVERAGE  MO 12.5 ST  2.2 OM  1.3 f0 6.48 R1.2239 AL 0.00 WI 20.0 MW  2.3 3
 2  SPEC SD       MO  0.7 ST  1.8 OM  0.7 f0 2.58 R2.8040 AL      WI      MW  0.5 3
 3  GAP=282        2.48      27.2    73.7 98.6 -0.1631E+04  0.5338E+04 -0.1724E+04E
 4  SPEC PB09BH Z MO 12.1 ST  1.5 OM  0.9 f0 8.00 R0.1480 AL-0.00 WI 20.0 MW  2.0 3
 5  SPEC PB09BH Z T 8 5 5 K 0.020 GD  159 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
 6  SPEC PB03BH Z MO 12.3 ST  2.6 OM  1.1 f0 8.00 R0.1480 AL-0.00 WI 20.0 MW  2.1 3
 7  SPEC PB03BH Z T 8 519 K 0.020 GD  173 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
 8  SPEC PB01BH Z MO 12.4 ST  3.4 OM  1.2 f0 8.00 R0.1480 AL-0.00 WI 20.0 MW  2.2 3
 9  SPEC PB01BH Z T 8 5 8 K 0.020 GD  174 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
10  SPEC PB07BH Z MO 12.2 ST  1.1 OM  1.0 f0 6.36 R0.1862 AL-0.00 WI 20.0 MW  2.1 3
11  SPEC PB07BH Z T 8 524 K 0.020 GD  179 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
12  SPEC PB08BH Z MO 14.4 ST0.002 OM  3.2 f00.137 R8.6423 AL-0.00 WI 20.0 MW  3.6 3
13  SPEC PB08BH Z T 8 517 K 0.020 GD  183 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
14  SPEC PB04BH Z MO 12.2 ST  2.2 OM  1.0 f0 8.00 R0.1480 AL-0.00 WI 20.0 MW  2.1 3
15  SPEC PB04BH Z T 8 530 K 0.020 GD  184 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
16  SPEC PB05BH Z MO 11.9 ST0.335 OM  0.7 f0 5.32 R0.2226 AL-0.00 WI 20.0 MW  1.9 3
17  SPEC PB05BH Z T 8 534 K 0.020 GD  187 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
18  SPEC PB11BH Z MO 12.7 ST  6.1 OM  1.4 f0 8.00 R0.1480 AL-0.00 WI 20.0 MW  2.4 3
19  SPEC PB11BH Z T 8 527 K 0.020 GD  200 VS 3.20 DE 2.60 Q0400.0 QA 0.70 Q1 1.00 3
20  2015-12-09-0803-18.TST___054_00_01                                            6
21  ACTION:NEW 15-12-09 08:04 OP:SEIS STATUS:               ID:20151209080418     I
22  STAT SP IPHASW D HRMM SECON CODA AMPLIT PERI AZIMU VELO AIN AR TRES W  DIS CAZ7
23  PB16 BZ IP    A   8 5  4.49  120
24  PB11 BZ IP    A   8 4 49.15  132
25  PB08 BZ IP    AC  8 4 43.76  105
26  PB01 BZ IP    A   8 4 38.26  125
27  PB07 BZ IP    A   8 4 39. 1  122
28  PB09 BZ IP    AC  8 4 33.65  121
29  PB03 BZ IP    A   8 4 37.56  113
30  PB04 BZ IP    A   8 4 41.36   89
31  PB06 BZ IP    A   8 4 36.51   86
32  PB05 BZ IP    A   8 4 42.61   87
33  PB15 BZ IP    A   8 4 37.86   94
34  PB11 BN IS   3A   8 5 28.64
35  PB08 BN IS   3A   8 5 19.16
36  PB01 BN IS   3A   8 5  9.81
37  PB06 BN IS   3A   8 5  7. 6
38  PB15 BN IS   3A   8 5  9.31
#   13  9 Dec 2015 08:03 54  LM-22.259 -66.832  0.0  N 1.2 2.3WBER   11  ?


next up previous contents index
Next: 21.3 AUTOSIG Up: 21. Automatic routines in Previous: 21.1 AUTOPIC and AUTO   Contents   Index
Peter Voss : Wed Aug 9 08:16:56 UTC 2017