27.3 Program CODAQ_POLYGON

Using EPIMAP, it is possible to select out events in a polygon when plotting the codaQ midpoints (or other epicentres). It is then possible to calculate the average Q in that area using the program CODAQ_POLYGON. The input polygon coordinates are assumed to be present in file epimap.cor, the one created by EPIMAP when selecting in a polygon. The codaQ values in the midpoints are supposed to be present in file codaq.area and no questions are asked. File coda1.out is also used as input and must be present. A depth range can be specified. The data in the polygon file is written out in a file POLYGON.MAP so it can be plotted again with EPIMAP. The POLYGON.MAP file is appended to so if CODAQ_AREA is used several times with different polygon areas, they will all be stored in POLYGON.MAP read for plotting with EPIMAP. It is up to the user to ensure the POLYGON.MAP is empty if a new series of polygons are stored.

The section of the codaq.area corresponding to the polygon area is output in codaq_polygon.area and it can be used with QSTAT for statistics of the data in the polygon area.

Example run

codaq_polygon c:\jens\Q-port\ALL>codaq_polygon Frequencies 1.00 2.00 4.00 8.00 16.00 Depth range to use, enter to use all Number of points defining polygon: 7 f= 1.00000000 f= 2.00000000 216. 269. 308. f= 4.00000000 696. 450. 602. 776. 677. 494. 614. 489. 707. 643. 764. 687. 649. 573. 816. 841. 834. 518. 536. 524. 786. f= 8.00000000 1366. 878. 968. 1295. 803. 999. 979. 967. 1155. 1080. 940. 1110. 1042. 994. 992. 999. 1023. 1020. 1009. 853. 1177. 1007. 1316. 1186. 777. 898. 959. 1052. 1097. 945. 1030. 1206. 1123. 1008. 1140. 1062. 1455. 1029. 1125. 809. 1298. 871. 1386. 1231. 1175. 1100. 771. 1171. 891. 897. 740. 1286. 1352. 1108. 1037. 1240. f= 16.0000000 1667. 1514. 1648. 1638. 1898. 1777. 1381. 1667. 1620. 1810. 1220. 1251. 1543. 1344. 1436. 1520. 1772. 1575. 1586. 1455. 1666. 1534. 1491. 1696. 1514. 1575. 1690. 1597. 1352. 1450. 1358. 1672. 1674. 1514. 1633. 1543. 1392. 1552. 1619. 1474. 1647. 1425. 1510. 1456. 1374. 1391. 1389. 1366. 1657. 1449. 1342. 1689. 1238. 1667. 2297. 1573. 1972. 1463. 1405. 1449. Number of Q-midpoints within polygon: 140 f= 2.0 av= 259.0 sd= 46.9 n= 3 f= 4.0 av= 628.9 sd= 119.7 n= 21 f= 8.0 av=1035.7 sd= 163.2 n= 56 f=16.0 av=1531.8 sd= 167.4 n= 60 q0= 172.7 sd 38.8 qalpha= 0.81 sd 0.10 q10=1107.8 sd=182.1 corr= 0.98 rms= 0.00 nf= 4 Use all data, no weight q0= 166.0 sd 36.8 qalpha= 0.84 sd 0.12 q10=1151.4 sd=188.4 corr= 0.98 rms= 0.00 nf= 4 Append to POLYGON.MAP (n/y=default) Accumulated polygon coordinates in POLYGON.MAP Area file selected is codaq_polygon.area oUput file is codaq_polygon.out

For each frequency, all the Q-values are printed so it is possible to get an idea of the variation of the values. The averages are calculated for each frequency if 2 or more values are available. The Q-realtion is then

calculated if averages are available for at least 3 frequecies. Finally, a Q-relation is calculated if also one value is available, but then there is no weighting with the standard deviations of the averages.

How to calculate coda Q in polygon areas

Calculate coda Q in large area of interest.

indexCoda Q in a polygon Plot all the midpoints between station end events with EPIMAP using command map codaq.area.nor . The input epicentre file is codaq.area.nor which is output from CODAQ.

Do the following for each polygon area:

With EPIMAP, use polygon function to select an area. Terminate EPIMAP.

Run codaq_polygon to calculate coda Q for that area, the polygon outline is stored in file

POLYGON.MAP for later plotting.

After e.g. 5 runs, the 5 areas are stored in POLYGON.MAP and the Q-relations have been printed out.

Peter Voss 2022-08-29T10:10Z | Please contact pv@geus.dk regarding the webpage, it is hosted by The Geological Survey of Denmark and Greenland (GEUS) | xxxxxxxxxxxyyyyyyyyyyyy