Location

2006/01/02 22:13:40 -19.88 -178.23 579

Moment Tensor Comparison

The following compares this source inversion to the USGS Rapid Moment Tensor Solution and to the Harvard CMT solutions, if they are available.

Mw=7.3 2006/01/02 22:13:40 EVID: LAT: 19.88S, LON: 178.23E, DEPTH: 620 Mw: 7.3, mb: 0.0, Ms: 0.0 Mo= 0.850E+27 (dyne-cm) No. of Stations: 26, GAP: 96 Error (clvd/dc)*100= 49.54 Nodal plane parameters strike dip rake NP1: 47 74 -100 NP2: 261 19 -58 ########## #################### #######-------------###### #####---------------------#### ####---------------------------- ###---------------------------###- ##----------------------------#####- ##----------------------------#######- #---------------------------########## #---------------------------############ #-------------------------############## -------------------------############### -----------------------################# --------------------################## -----------------##################### --------------###################### ----------######################## ------########################## ############################## ########################## #################### ########## Stat Dist Az Misfit Stat Dist Az Misfit ANMO 87 51 0.54 BILL 88 354 0.38 BOZ 88 40 0.56 CMB 79 42 0.47 COCO 81 260 0.18 COLA 87 12 0.31 CTAO 33 263 0.24 EFI 91 147 0.46 GUMO 49 309 0.25 HLID 86 40 0.61 INCN 77 317 0.30 INK 93 15 0.40 KWAJ 31 332 0.48 MA2 83 344 0.47 MAJO 69 323 0.22 MOD 81 39 0.47 MSO 88 38 0.48 NWAO 58 242 0.49 PET 75 345 0.34 SIT 84 21 0.50 TATO 73 304 0.32 TUC 82 52 0.46 WDC 79 39 0.48 WMOK 92 54 0.65 YAK 91 338 0.31 YSS 75 333 0.33 Misfit > 1 heavily downweighted

Mw=7.1 FIJI REGION 2006/01/02 22:13:40.30 EVID: HKAX LAT: 19.88S, LON: 178.23W, DEPTH: 580 Mw: 7.1, mb: 7.1, Ms: 7.1 Mo= 0.479E+27 (dyne-cm) No. of Stations: 26, GAP: 96 Error (clvd/dc)*100= 47.18 Nodal plane parameters strike dip rake NP1: 61 75 248 NP2: 298 26 -36 ########## #################### ########----############## ###------------------######### #------------------------####### ----------------------------###### -------------------------------###-- -------------------------------------- --------------------------------###--- -------------------------------######--- ----------------------------#########--- --------------------------############-- -----------------------###############-- ------------------###################- --------------#######################- --------############################ ################################## ################################ ############################## ########################## #################### ########## Stat Dist Az Misfit Stat Dist Az Misfit ANMO 87 51 0.57 BILL 88 354 0.16 BOZ 88 40 0.57 CMB 79 42 0.33 COCO 81 260 0.29 COLA 87 12 0.14 CTAO 33 263 0.40 EFI 91 147 0.44 GUMO 49 309 0.37 HLID 86 40 0.69 INCN 77 317 0.21 INK 93 15 0.21 KWAJ 31 332 0.64 MA2 83 344 0.23 MAJO 69 323 0.27 MOD 81 39 0.38 MSO 88 38 0.36 NWAO 58 242 0.17 PET 75 345 0.26 SIT 84 21 0.53 TATO 73 304 0.24 TUC 82 52 0.43 WDC 79 39 0.37 WMOK 92 54 0.63 YAK 91 338 0.18 YSS 75 333 0.25 Median of misfit: 0.35 Average misfit: 0.36

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: ANMO BILL BOZ CMB COCO COLA CTAO EFI GUMO HLID INCN INK KWAJ MA2 MAJO MOD MSO NWAO PET SIT TATO TUC WDC WMOK YAK YSS

Location of the earthquake (yellow star) and great circle path from the epicenter to each station (red) [created using GMT (Wessel, P., and W. H. F. Smith, New version of Generic Mapping Tools released, EOS Trans. AGU, 76 329, 1995.)]

The traces were next integrated to ground displacment in meters. Finally waveforms were cut from 30 seconds before to 140 seconds after the P arrival so that the direct P wave, pP and perhaps the sP are included.

The source inversion is a multipass operation since a lower frequency filter band is used for larger earthquakes and since a search is made over depth. Up to three passed of the outer loop are made, after which the moment magnitude is determined and filter settings readjusted. The inner loop over depth samples all depths from 0 to 800 km with 5 km increments in depth to 50 km, followed by 10 km depth sampling for the remaining range.

The following filter ranges are used according to the moment magnitude Mw:

   FILTER_BAND   FH(s)  FL(s)
       1           60     12      Mw < 6.4
       2          100     20      6.4 < Mw <= 6.9
       3          120     40      Mw > 6.9

For this data set the favored solution is

WVFMTD96  620.0   47.   74. -100.   7.25     0.647 0.238E-05     0.647     0.831 0.238E-05  49.5

The following figures show the sensitivity of the goodness of fit parameter so source depth, the waveform comparison as a function of epicentral distance in degrees and the source to station azimuth

Depth Sensitivity

Goodness of fit as a function of source depth. The measure is 1 - SUM (o -p)2 / SUM o2. A value of 1.0 is the best fit. The best double couple mechanism for the solution depth is plotted above goodness of fit value to indicate how the mefhanism may change with depth.

Fit with Distance

Fit with Azimuth

Comparison of the observed traces (red) and solution predicted traces (blue) as a function of source to station azimuth in degrees (D). The purpose of this display is to highlight the azimuthal dependence on the first motion. The traces are annotated with the station name at the top.

Inversion Details