Min-Hung Shih 1/22/2015 Ver. 0.4
Quick View 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
dbdetect.pf Globel parameters Design multi-filters Assign station & channel reject 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
ttgrid.pf Design grid 1 Design grid 2 Deisgn grid 3 Design grid 4 grid name ( remember the grid names and how many grids you have !! )
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 step3 Execute dbgrassoc >dbgrassoc -pf dbgrassoc.pf dbin dbout grid_file
dbgrassoc.pf define the parameters for each grids in grid_file Put your grid name here !!
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 !!!