Changes between Version 3 and Version 4 of pick_ew


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Timestamp:
05/06/12 10:45:15 (8 years ago)
Author:
branden
Comment:

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  • pick_ew

    v3 v4  
    111111Function: output 
    112112 
    113 Sets maxgap, the maximum length (in samples) of a data gap which pick_ew will allow without restarting the picking algorithm. When pick_ew detects a data gap less than or equal to maxgap samples on a given channel, it will do a simple linear interpolation across the gap and continue in the picking algorithm as if there were no data gap. If a gap is longer than maxgap samples, then pick_ew will drop all active pick and coda calculations for that channel and will enter the "restart" phase (see RestartLength command) of the algorithm. 
     113Sets maxgap, the maximum length (in samples) of a data gap which pick_ew will allow without restarting the picking algorithm. When pick_ew detects a data gap less than or equal to maxgap samples on a given channel, it will do a simple linear interpolation across the gap and continue in the picking algorithm as if there were no data gap. If a gap is longer than maxgap samples, then pick_ew will drop all active pick and coda calculations for that channel and will enter the "restart" phase (see !RestartLength command) of the algorithm. 
    114114{{{ 
    115115Default:  none 
     
    130130 
    131131'''!NoCoda [flag]'''[[BR]] 
    132 Processed by: GetConfig[[BR]] 
     132Processed by: !GetConfig[[BR]] 
    133133Function: picking params 
    134134 
     
    205205'''Channel Identification:''' 
    206206 
    207  1. Pick Flag: if Pick Flag is 0, pick_ew will not try to pick P-wave arrivals from this trace.  If Pick Flag is 1, the trace will be picked. 
    208  
    209  2. Pin Numb: this field is not used by pick_ew, but exists for posterity and for potential use by other programs.  Each input signal in a given Earthworm system should have a pin number Pin Numb (2-byte integer) that is unique across all data sources within the system. For example,  
    210 if we use two digitizers with 256 channels each, our pin numbers would range from 0 to 511. 
    211  
    212  3. Station: the first of 3 fields (Station-Comp-Net) that will uniquely identify each trace of seismic data.  Station is a string, up to 5 characters, that identifies the physical site of the seismic instrument. This label must be unique within a given network. 
    213     
    214  4. Comp: a 3-character string to identify the component of motion recorded by this seismic trace. 
    215     
    216  5. Net: a 2-character string that identifies the network that operates the seismic instrument. 
    217  
    218  6. Loc: a 2-character string that identifies the location code that describes the sensor location. 
     2071. Pick Flag: if Pick Flag is 0, pick_ew will not try to pick P-wave arrivals from this trace.  If Pick Flag is 1, the trace will be picked. 
     208 
     2092. Pin Numb: this field is not used by pick_ew, but exists for posterity and for potential use by other programs.  Each input signal in a given Earthworm system should have a pin number Pin Numb (2-byte integer) that is unique across all data sources within the system. For example, if we use two digitizers with 256 channels each, our pin numbers would range from 0 to 511. 
     210 
     2113. Station: the first of 3 fields (Station-Comp-Net) that will uniquely identify each trace of seismic data.  Station is a string, up to 5 characters, that identifies the physical site of the seismic instrument. This label must be unique within a given network. 
     212    
     2134. Comp: a 3-character string to identify the component of motion recorded by this seismic trace. 
     214    
     2155. Net: a 2-character string that identifies the network that operates the seismic instrument. 
     216 
     2176. Loc: a 2-character string that identifies the location code that describes the sensor location. 
    219218 
    220219'''Event Termination/ Evaluation Criteria:''' 
    221220 
    222  7. Itr1: (i5 in earlier code) Sets Itr1 which is used to calculate the zero-crossing termination count.  The pick_ew calculates itrm, the number of consecutive small-zero crossings (zero-crossings where the short-term average is less than the critical termination level) to be allowed before declaring the event over. itrm = Itr1 + m / Itr1 where m is the zero-crossing counter. itrm will start out quite small at the beginning of an event and will increase during an event to a maximum of 50. 
    223     
    224  8. MinSmallZC: (i6 in earlier code) Defines the minimum number of zero-crossings for a valid pick.  An event is declared over and potentially valid after MinSmallZC zero-crossings. Pick_ew then evaluates the event to determine if it was a seismic event or noise. 
    225   
    226  9. MinBigZC: (i7 in earlier code) Defines the minimum number of "big zero-crossings" for a valid pick. No pick is reported unless at least MinBigZC big zero-crossings occurred while the event was active.  [A "big zero-crossing" amplitude must exceed rbig, where rbig is (the largest amplitude of first 3 half-cycles after event activation)/3.  A "big zero crossing" must also represent a crossing of opposite polarity to the previous crossing]. 
    227  
    228  10. MinPeakSize: (i8 in earlier code) Defines the minimum amplitude (digital counts) for a valid pick. No pick is reported unless one of the first three peaks of an event has an amplitude larger than MinPeakSize digital counts. 
    229   
    230  11. MaxMint: (hard-wired at 500 in earlier code) Maximum interval (in samples) between zero crossings. If no zero crossings occur within MaxMint data samples, the pick event is terminated. 
    231   
    232  12. i9:        (i9 in earlier code) Defines the minimum coda length (seconds) for a valid pick.  No pick is reported unless its coda is at least i9 seconds long. 
     2217. Itr1: (i5 in earlier code) Sets Itr1 which is used to calculate the zero-crossing termination count.  The pick_ew calculates itrm, the number of consecutive small-zero crossings (zero-crossings where the short-term average is less than the critical termination level) to be allowed before declaring the event over. itrm = Itr1 + m / Itr1 where m is the zero-crossing counter. itrm will start out quite small at the beginning of an event and will increase during an event to a maximum of 50. 
     222    
     2238. MinSmallZC:  (i6 in earlier code) Defines the minimum number of zero-crossings for a valid pick.  An event is declared over and potentially valid after MinSmallZC zero-crossings. Pick_ew then evaluates the event to determine if it was a seismic event or noise. 
     224  
     2259. MinBigZC: (i7 in earlier code) Defines the minimum number of "big zero-crossings" for a valid pick. No pick is reported unless at least MinBigZC big zero-crossings occurred while the event was active.  [A "big zero-crossing" amplitude must exceed rbig, where rbig is (the largest amplitude of first 3 half-cycles after event activation)/3.  A "big zero crossing" must also represent a crossing of opposite polarity to the previous crossing]. 
     226 
     22710. !MinPeakSize: (i8 in earlier code) Defines the minimum amplitude (digital counts) for a valid pick. No pick is reported unless one of the first three peaks of an event has an amplitude larger than !MinPeakSize digital counts. 
     228  
     22911. !MaxMint: (hard-wired at 500 in earlier code) Maximum interval (in samples) between zero crossings. If no zero crossings occur within !MaxMint data samples, the pick event is terminated. 
     230  
     23112. i9: (i9 in earlier code) Defines the minimum coda length (seconds) for a valid pick.  No pick is reported unless its coda is at least i9 seconds long. 
    233232 
    234233'''Waveform Filtering Parameters:''' 
    235234 
    236  13. RawDataFilt: (c1 in earlier code) Sets the filter parameter RawDataFilt that is applied to the raw trace data.  This is essentially a recursive highpass filter that removes the DC offset from the data. 
    237  
    238  14. CharFuncFilt: (c2 in earlier code) Sets the filter parameter CharFuncFilt that is applied in the calculation of the characteristic function of the waveform data. 
    239   
    240  15. StaFilt: (c3 in earlier code) Sets the filter parameter (time constant) StaFilt that is used in the calculation of the short-term average (STA) of the characteristic function of the trace. 
    241   
    242  16. LtaFilt: (c4 in earlier code) Sets the filter parameter (time constant) LtaFilt that is used in the calculation of the long-term average (LTA) of the characteristic function of the trace. 
    243     
    244  17. EventThresh: (c5 in earlier code) Sets the STA/LTA event threshold.  An event (a pick) is declared when STA is larger than EventThresh*LTA.  Once an event is declared, pick_ew enters an event evaluation mode to determine if the event is a P-wave arrival or noise. 
    245     
    246  18. RmavFilt: Filter parameter (time constant) used to calculate the running mean of the absolute value of the waveform data. Usually set to 0.9961. 
    247  
    248  19. DeadSta: (c6 in earlier code) Sets the dead station threshold (counts). If the running average of the absolute value (AAV) of a trace is           greater than DeadSta digital counts, the channel is considered dead and the pick_ew does not attempt to pick arrivals. 
     23513. !RawDataFilt: (c1 in earlier code) Sets the filter parameter !RawDataFilt that is applied to the raw trace data.  This is essentially a recursive highpass filter that removes the DC offset from the data. 
     236 
     23714. !CharFuncFilt: (c2 in earlier code) Sets the filter parameter !CharFuncFilt that is applied in the calculation of the characteristic function of the waveform data. 
     238  
     23915. !StaFilt: (c3 in earlier code) Sets the filter parameter (time constant) !StaFilt that is used in the calculation of the short-term average (STA) of the characteristic function of the trace. 
     240  
     24116. !LtaFilt: (c4 in earlier code) Sets the filter parameter (time constant) !LtaFilt that is used in the calculation of the long-term average (LTA) of the characteristic function of the trace. 
     242    
     24317. !EventThresh: (c5 in earlier code) Sets the STA/LTA event threshold.  An event (a pick) is declared when STA is larger than !EventThresh*LTA.  Once an event is declared, pick_ew enters an event evaluation mode to determine if the event is a P-wave arrival or noise. 
     244    
     24518. !RmavFilt: Filter parameter (time constant) used to calculate the running mean of the absolute value of the waveform data. Usually set to 0.9961. 
     246 
     24719. !DeadSta: (c6 in earlier code) Sets the dead station threshold (counts). If the running average of the absolute value (AAV) of a trace is           greater than !DeadSta digital counts, the channel is considered dead and the pick_ew does not attempt to pick arrivals. 
    249248 
    250249'''Coda Termination Parameters:''' 
    251250 
    252  20. CodaTerm: (c7 in earlier code) Sets the "normal" coda termination threshold (counts). Two methods are used to determine if the coda length calculation is over.  For quiet stations, the coda is "normally" terminated when the AAV of a 2-second waveform window drops below CodaTerm digital counts.  For noisy stations, an alternate termination method is used (see AltCoda & PreEvent, below).  Pick_ew stops all coda calculations 144 seconds after event activation, even if the coda AAV hasn't reached the termination value.  In the Northern California Seismic Network's convention, CodaTerm is the number of digital counts produced by a discriminator output signal (input to the Earthworm A/D) of 60 mV. The 2-bit Earthworm A/D has an input range of +/- 2.5 volts and an output range of 0 to 4095 counts (-2048 to 2047 counts).  For such a system, a 60 mV input will produce a sample of 49.1 counts. 
    253  
    254  21. AltCoda: (c8 in earlier code) Defines the "noisy station level" at which pick_ew should use the alternate coda termination method.  If the                 AAV of a channel is greater than CodaTerm*AltCoda digital counts when an event is declared, pick_ew uses the alternate coda termination method. 
    255     
    256  22. PreEvent: (c9 in earlier code) Defines the alternate coda termination threshold for noisy stations. If the AAV of a channel is greater than                CodaTerm*AltCoda digital counts when an event is declared, the coda is considered over when the AAV of a 2-second waveform window drops to              less than PreEvent*(pre-event signal amplitude).  Pick_ew stops all coda calculations 144 seconds after event activation, even if the coda AAV hasn't reached the termination value. 
    257  
    258  23. Erefs: (hard-wired at 50000. in earlier code) Used in calculating the increment (crtinc) to be added to the criterion level (ecrit) at each zero crossing. The criterion level is used to determine if the event is over. crtinc = eref / Erefs where eref is the current STA/LTA reference level. The smaller Erefs is, the faster ecrit will increase, and the sooner the event will terminate. 
     25120. !CodaTerm: (c7 in earlier code) Sets the "normal" coda termination threshold (counts). Two methods are used to determine if the coda length calculation is over.  For quiet stations, the coda is "normally" terminated when the AAV of a 2-second waveform window drops below !CodaTerm digital counts.  For noisy stations, an alternate termination method is used (see !AltCoda & !PreEvent, below).  Pick_ew stops all coda calculations 144 seconds after event activation, even if the coda AAV hasn't reached the termination value.  In the Northern California Seismic Network's convention, !CodaTerm is the number of digital counts produced by a discriminator output signal (input to the Earthworm A/D) of 60 mV. The 2-bit Earthworm A/D has an input range of +/- 2.5 volts and an output range of 0 to 4095 counts (-2048 to 2047 counts).  For such a system, a 60 mV input will produce a sample of 49.1 counts. 
     252 
     25321. !AltCoda: (c8 in earlier code) Defines the "noisy station level" at which pick_ew should use the alternate coda termination method.  If the                 AAV of a channel is greater than !CodaTerm*!AltCoda digital counts when an event is declared, pick_ew uses the alternate coda termination method. 
     254    
     25522. !PreEvent: (c9 in earlier code) Defines the alternate coda termination threshold for noisy stations. If the AAV of a channel is greater than                !CodaTerm*!AltCoda digital counts when an event is declared, the coda is considered over when the AAV of a 2-second waveform window drops to            less than !PreEvent*(pre-event signal amplitude).  Pick_ew stops all coda calculations 144 seconds after event activation, even if the coda AAV hasn't reached the termination value. 
     256 
     25723. Erefs: (hard-wired at 50000. in earlier code) Used in calculating the increment (crtinc) to be added to the criterion level (ecrit) at each zero crossing. The criterion level is used to determine if the event is over. crtinc = eref / Erefs where eref is the current STA/LTA reference level. The smaller Erefs is, the faster ecrit will increase, and the sooner the event will terminate. 
    259258 
    260259'''Optional Parameters:''' 
    261260 
    262  24. ClipCount: (added in v5.1 for use by eqcoda, ignored by pick_ew) Specifies the maximum absolute amplitude (in counts zero-to-peak) that can be expected for this channel. Eqcoda calculates clipping thresholds for P-amplitudes and coda-window average absolute amplitudes as a fraction of ClipCount.    
     26124. !ClipCount: (added in v5.1 for use by eqcoda, ignored by pick_ew) Specifies the maximum absolute amplitude (in counts zero-to-peak) that can be expected for this channel. Eqcoda calculates clipping thresholds for P-amplitudes and coda-window average absolute amplitudes as a fraction of !ClipCount.    
    263262 
    264263=== ADDITIONAL REFERENCES ON THE PICKER ALGORITHM ===