dbdetect

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Min-Hung Shih
1/22/2015 Ver. 0.4
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Run dbdetect to execute STA/LTA
detectors on the waveforms
 Run dbpick on the database to modify
picks
 Run ttgrid to make a grid file
 Run dbgrassoc to produce origin and
event tables
 Run dbloc2 on the database to modify
picks and calculate earthquake locations

dbdetect
 dbdetect
runs STA/LTA algorithm on
seismic data to determine the arrival
times of seismic energy.
step1
Copy parameter file
on local directory
>pfcp dbdetect
your_directory
step2
Edit dbdetect.pf
>vi dbdetect.pf
step3
Execute dbdetect
>dbdetect -arrivals
-pf pffile dbin dbout
STA/LTA algorithm
STA/LTA 運算程序,就是利用所謂的
「短時窗信號平均值」與「長時窗信號平
均值」的比值,判讀地震訊號
 STA為Short Time Average之縮寫,也就
是短時窗信號平均值,另一要素為LTA,
是Long Time Average之縮寫,也就是長
時窗信號平均值,當STA除以LTA之值大
於設定值(threshold)時,即視為地震訊號

STA window
LTA window
Globel parameters
dbdetect.pf
reject station & channel
Design multi-filters
Assign station & channel
Design multi-filter for
individual station & channel
dbpick - check arrivels
ttgrid

Compute a travel time grid file
step1
Copy paraneter file
on local directory
>pfcp ttgrid
your_directory
step2
Edit ttgrid.pf
>vi ttgrid.pf
step3
Execute ttgrid
>ttgrid -pf ttgrid.pf
-time all db > grid_file
step4
Display the grid
>displayttgrid grid_file
grid_name
grid name ( remember the
grid names and how many
grids you have !! )
ttgrid.pf
Design grid 2
Deisgn grid 3
Design grid 1
Design grid 4
displayttgrid (check your grid)
dbgrassoc
 dbgrassoc
spatial grid search based
associator/locator
step1
Copy paraneter file
on local directory
>pfcp dbgrassoc
your_directory
step2
Edit dbgrassoc.pf
>vi dbgrassoc.pf
Execute dbgrassoc
>dbgrassoc -pf
dbgrassoc.pf dbin
dbout grid_file
step3
dbgrassoc.pf
Put your grid name here !!
define the parameters for each grids
in grid_file
Output files of dbgrassoc
db.origin - hypocenter parameters
 db.event - the preferred origin for an event
 db.arrival - phase, time of the seismic arrivals
 db.assoc - connects arrival to origin, list travel
time residuals, etc.

dbloc2 - Interactive hypocenter location

>dbloc2 dbname
Practice !!!

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