Changes between Version 5 and Version 6 of glass


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Timestamp:
05/29/12 13:04:55 (8 years ago)
Author:
branden
Comment:

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  • glass

    v5 v6  
    7373!TimeStep 5.0 
    7474 
    75 appears in the glass_assoc.d config file. The Nucleator iterates through a set of trial origin times within the potential origin time window. The time delta between iterations in seconds is defined by the !TimeStep command. So if !TimeStep is 5.0, then the Nucleator will iterate between origins that are 5 seconds apart. The smaller the !TimeStep value, the closer the Nucleator should be to the actual origin time and the more processing iterations that will have to be done, so there is a tradeoff between accuracy and processing effort. There are two factors that affect what the TimeStep value should be set to: residual distance limits and locator ability. Because the Nucleator fixes the origin time and depth, any residuals are distance based. If the TimeStep value is set too high, then it increases the artificial distance residual that may be imposed on an origin because the actual event time lay between two iterative steps. So if an event occurs at time 1232.5, !TimeStep is set to 5, and the closest two origin time iterations are 1230.0 and 1235.0, then an artificial time residual of 2.5 seconds is being imposed on the nucleated origin. Because the Nucleator deals only in distance residuals, that 2.5 seconds becomes converted to a distance value. When that residual distance value gets to be too great then the Nucleator will no longer be able to associate the origin. The Nucleator is a tool to associate picks into an Origin, its association is not meant to be the Glass end-all final location answer. Within Glass there is a Locator that will refine solutions after they come out of the Nucleator. So a TimeStep value must be chosen that is not too processing intensive but is also not so wide as to preclude origins based on the artificial residuals between time iterations and actual event time. A !TimeStep of 5.0, results in a maximum artificial window of 2.5 seconds, with a maximum P velocity of about 13km/sec, that ends up at a worst case artificial distance residual of 32km. If the distance Cut is set to 50km, this leaves only 18km available for anomalies due to actual vs. theoretical 1-d travel times, and depth iteration intervals. 
     75appears in the glass_assoc.d config file. The Nucleator iterates through a set of trial origin times within the potential origin time window. The time delta between iterations in seconds is defined by the !TimeStep command. So if !TimeStep is 5.0, then the Nucleator will iterate between origins that are 5 seconds apart. The smaller the !TimeStep value, the closer the Nucleator should be to the actual origin time and the more processing iterations that will have to be done, so there is a tradeoff between accuracy and processing effort. There are two factors that affect what the !TimeStep value should be set to: residual distance limits and locator ability. Because the Nucleator fixes the origin time and depth, any residuals are distance based. If the !TimeStep value is set too high, then it increases the artificial distance residual that may be imposed on an origin because the actual event time lay between two iterative steps. So if an event occurs at time 1232.5, !TimeStep is set to 5, and the closest two origin time iterations are 1230.0 and 1235.0, then an artificial time residual of 2.5 seconds is being imposed on the nucleated origin. Because the Nucleator deals only in distance residuals, that 2.5 seconds becomes converted to a distance value. When that residual distance value gets to be too great then the Nucleator will no longer be able to associate the origin. The Nucleator is a tool to associate picks into an Origin, its association is not meant to be the Glass end-all final location answer. Within Glass there is a Locator that will refine solutions after they come out of the Nucleator. So a !TimeStep value must be chosen that is not too processing intensive but is also not so wide as to preclude origins based on the artificial residuals between time iterations and actual event time. A !TimeStep of 5.0, results in a maximum artificial window of 2.5 seconds, with a maximum P velocity of about 13km/sec, that ends up at a worst case artificial distance residual of 32km. If the distance Cut is set to 50km, this leaves only 18km available for anomalies due to actual vs. theoretical 1-d travel times, and depth iteration intervals. 
    7676 
    7777 
     
    118118The Nucleator is fairly sensitive to the affects of noisy stations. If you have stations that consistently generate non-relative picks, you may wish to remove them from the station list. Noisy stations will often generate picks that are ripe for coincidental associations which can corrupt origin parameters, causing false or mislocated earthquakes. 
    119119 
    120 Glass currently uses the list of stations specified in the Glass_data\stalist.hinv file (a list of stations in HypoInverse station list format). The lower the number of Cut points, the more sensitive the Nucleator will be to noise picks. Glass must be restarted in order for station list file changes to take effect. There is no way to adjust the station list on the fly during runtime. Glass will ignore all picks received from channels that are not in the station list 
     120Glass currently uses the list of stations specified in the Glass_data\stalist.hinv file (a list of stations in !HypoInverse station list format). The lower the number of Cut points, the more sensitive the Nucleator will be to noise picks. Glass must be restarted in order for station list file changes to take effect. There is no way to adjust the station list on the fly during runtime. Glass will ignore all picks received from channels that are not in the station list 
    121121 
    122122===== Parameters Untunable =====  
     
    179179ResWinWidth      15.0 
    180180}}} 
    181 The above paragraph tells the program that generates the traveltime tables to generate one for the phase PKKP, to be named PKKPbc, to generate it over the distance range of 85 to 125 degrees with an entry every 2.5 degrees, for a depth range of 0 to 800 with an entry every 25km; it also tells it to generate a reverse lookup table based on time/depth, with entries every 10 seconds / 25km. It tells it to only use PKKP phases with ray params between 2 and 4.112 (the bc branch but not the ab). The LocWeight entry is not important to the Associator but effects the weight given to this phase by the Glass Locator. The last entry is SIGNIFICANT with respect to the Residual affinity statistic. It tells the Associator to use a 15 second residual window (half-width) for this phase, instead of the default of 10. The residual affinity statistic is calculated based on the ratio of the residual to the allowable residual window. 
     181The above paragraph tells the program that generates the traveltime tables to generate one for the phase PKKP, to be named PKKPbc, to generate it over the distance range of 85 to 125 degrees with an entry every 2.5 degrees, for a depth range of 0 to 800 with an entry every 25km; it also tells it to generate a reverse lookup table based on time/depth, with entries every 10 seconds / 25km. It tells it to only use PKKP phases with ray params between 2 and 4.112 (the bc branch but not the ab). The !LocWeight entry is not important to the Associator but effects the weight given to this phase by the Glass Locator. The last entry is SIGNIFICANT with respect to the Residual affinity statistic. It tells the Associator to use a 15 second residual window (half-width) for this phase, instead of the default of 10. The residual affinity statistic is calculated based on the ratio of the residual to the allowable residual window. 
    182182 
    183183The generation program will generate a table for each configuration paragraph. Actually two tables get generated: one based on time/depth and one on distance/depth. Each entry in these tables will contain the following information: 
     
    420420The Location Weight is set in the traveltime tables.  See Tunable Affinity 
    421421Statistics Traveltime Tables under the Associator section for a description 
    422 of traveltime table parameters.  Setting LocWeight to a value will cause the 
     422of traveltime table parameters.  Setting !LocWeight to a value will cause the 
    423423Locator to apply that weight to picks of that phase.  The default weight 
    424424is 1.0.