Changes between Version 2 and Version 3 of glass


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Timestamp:
05/29/12 11:56:00 (8 years ago)
Author:
branden
Comment:

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  • glass

    v2 v3  
    2525 * The User section contains minimal information on the interactive use of the Glass GUI displays. 
    2626 
    27 === Seismologist/Network Operator === 
     27=== Seismologist/ Network Operator === 
    2828 
    2929Glass can be thought of as having four(4) major mechanisms for producing earthquake information (origins and associated phases): Nucleator, Associator, Locator, and Filter. The Nucleator creates new earthquake origins, the Associator associates picks with existing origins, the Locator refines origin hypocenters, and the Filter eliminates origins and origin-pick associations. 
     
    5050 6. Station List 
    5151 
    52 ====== Location Points ====== 
     52''Location Points'' 
    5353 
    5454A line similar to the following: 
     
    5858appears in the glass_assoc.d config file. The Cut command takes two arguments: number of location points, and distance threshold. When the Nucleator is evaluating potential origins, it calculates nth-point-distance for each potential origin for each time/depth iteration. The first argument defines n (the number of points), and the second argument defines the distance threshold of acceptable origins. So Cut 9 50.0, would instruct the Nucleator to require 9 points to be within 50km of a perspective origin on The Ring, in order for that origin to be deemed acceptable. Note that the Nucleator counts the central point in the 9, so there are only required to be 8 (n-1) other points within the distance. n in theory controls the number of points required in a proximate distance, but in practice, it can be used to determine the number of P-phases required to associate an origin. 
    5959 
    60 ====== Time Windows ====== 
     60''Time Windows'' 
    6161 
    6262A line similar to the following: 
     
    6767 
    6868 
    69 ====== Time Iterations ====== 
     69''Time Iterations'' 
    7070 
    7171A line similar to the following: 
     
    7676 
    7777 
    78 ====== Depth Iterations ====== 
     78''Depth Iterations'' 
    7979 
    8080Lines similar to the following: 
     
    9292 
    9393 
    94 ====== Travel-time Tables ====== 
     94''Travel-time Tables'' 
    9595 
    9696The Nucleator and the rest of Glass use the Hydra traveltime libraries to access data stored in traveltime tables. At this point Glass uses a special subset of traveltime tables that were generated based on empirical ad-hoc observations regarding the phases being picked by the Hydra picker. The actual traveltime tables used by Glass are defined in the tt_tables.d config file in the Hydra params directory. The individual traveltime files must be generated by a separate program. See Generating Traveltime Tables in the Programmer section of this document, or find a developer to do it for you. 
     
    114114The Nucleator makes use of only P phases from the crust/mantle. The current list includes (Pg, Pb, Pn, p, P, Pdif), and only the Traveltime, Depth, and Distance information. Under the current code, there is probably not much that should/could be altered in the traveltime tables that would affect the Nucleator. 
    115115 
    116 ====== Station List ====== 
     116''Station List'' 
    117117 
    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. 
     
    153153The traveltime tables and station list are currently tunable. The affinity statistic coefficients defined in the traveltime tables are tunable, but the others that are hardcoded within the Glass program are not. 
    154154 
    155 ====== Travel-time Tables ====== 
     155''Travel-time Tables'' 
    156156 
    157157Please see Travel-time Tables under The Nucleator for an overview of the traveltime tables. At this point Glass uses a special subset of traveltime tables that were generated based on empirical ad-hoc observations regarding the phases being picked by the Hydra picker. 
     
    160160 
    161161 
    162 ====== Station List ====== 
     162''Station List'' 
    163163 
    164164The Associator requires two sets of inputs in order to perform an association: a traveltime table for the appropriate distance/time, and a pick. If there are no picks, there will be no associations. So associations can be limited by limiting the available picks. Whether or not to limit legitimate energy picks in order to get better answers out of Glass is a question that's above my position on the seismology scale; however, limiting noisy stations that do not contribute picks that are relative to your end goal is a recommended activity. For example, if you are interested in locating medium to large global earthquakes, then you probably do not want to include stations with faulty electronics, stations with a lot of non-seismic noise (traffic, oceans, ice breaking), or stations that are located close to an active seismic source that constantly releases energy in small magnitudes. Noisy stations will often generate picks that are ripe for coincidental associations. This can corrupt origin parameters, causing false or mislocated earthquakes. 
    165165 
    166166 
    167 ====== Tunable Affinity Statistics Traveltime Tables ====== 
     167''Tunable Affinity Statistics Traveltime Tables'' 
    168168 
    169169Traveltime tables are generated by a separate program, which is not currently setup for seismologist operation. There are a number of configuration files that are used as input to the traveltime table generation program, that can be edited by a seismologist. These input files currently live in hydra_proj\params\resp\seismic\ttt\glass\*.txt. In these files, a configuration paragraph similar to the following appears for each traveltime table. 
     
    196196===== Parameters - Untunable ===== 
    197197 
    198 Affinity Statistic 
     198''Affinity Statistic'' 
    199199 
    200200Most of the components of the affinity statistic generated for an origin-pick association are not tunable. The composite affinity statistic is generated via the following equation: