Auto-location and manual location in Antelope Min-Hung Shih 10/13/2011 Ver. 0.3

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 step1 step2 step3 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 reject station & channel Design multi-filter for individual station & channel Design multi-filters Assign station & channel

dbpick - check arrivels

ttgrid step1 step2 step3 step4 Compute a travel time grid file 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 step1 step2 step3 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 !! 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 !!!