Location

2006/04/07 08:30:43 -16.62 177.00 7

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=6.5 2006/04/07 08:30:43 EVID: LAT: 16.62S, LON: 177.00E, DEPTH: 15 Mw: 6.5, mb: 0.0, Ms: 0.0 Mo= 0.559E+26 (dyne-cm) No. of Stations: 11, GAP: 272 Error (clvd/dc)*100= 3.52 Bandpass: 20 - 100 sec Nodal plane parameters strike dip rake NP1: 81 83 7 NP2: 351 83 173 ##--------- #######------------ ###########-------------- #############---------------- #############----------------- # T #############------------------ ## ##############------------------ ####################------------------- #####################-------------------- ######################------------------- ######################---------------#### ######################--------########### ####################---################## -----------------------################## -----------------------################## ----------------------################# ----------------------############### ---------------------############## --------------------############# - --------------########### P --------------######### -------------###### ---------## Stat Dist Az Misfit Stat Dist Az Misfit BW06 89 44 0.50 CMB 79 45 0.41 HLID 86 42 0.56 ISCO 91 48 0.47 MA2 78 346 0.53 MAJO 64 325 0.41 MOD 82 42 0.51 NEW 87 37 0.44 TPNV 82 47 0.49 TUC 84 54 0.49 WDC 79 42 0.45 Misfit > 1 heavily downweighted

2006/04/07 08:30:43.26 EVID: LFAL LAT: 16.62S, LON: 177.00E, DEPTH: 10 Mw: 6.3, mb: 6.3, Ms: 6.3 Mo= 0.373E+26 (dyne-cm) No. of Stations: 11, GAP: 272 Error (clvd/dc)*100= 13.92 Nodal plane parameters strike dip rake NP1: 84 84 12 NP2: 353 78 174 ###------- #########----------- ############-------------- ###############--------------- #################--------------- ##################---------------- ###################----------------- #####################----------------- #####################----------------- #######################----------------- #######################-------------#### #######################--############### -----------------------################# ----------------------################ ----------------------################ ---------------------############### ---------------------############# -------------------############# ------------------############ ----------------########## -------------####### --------## Stat Dist Az Misfit Stat Dist Az Misfit BW06 89 44 0.80 CMB 79 45 0.76 HLID 86 42 0.83 ISCO 91 48 0.82 MA2 78 346 0.67 MAJO 64 325 0.72 MOD 82 42 0.86 NEW 87 37 0.81 TPNV 82 47 0.81 TUC 84 54 0.83 WDC 79 42 0.79 Median of misfit: 0.81 Average misfit: 0.79

April 7, 2006, FIJI, MW=6.4 Natasha Maternovskaya CENTROID, MOMENT TENSOR SOLUTION HARVARD EVENT-FILE NAME C040706A DATA USED: GSN L.P. BODY WAVES: 79S,188C, T= 40 MANTLE WAVES: 77S,159C, T=125 CENTROID LOCATION: ORIGIN TIME 08:30:50.9 0.1 LAT 16.51S 0.01;LON 177.08E 0.01 DEP 12.0 FIX;HALF-DURATION 4.1 MOMENT TENSOR; SCALE 10**25 D-CM MRR= 0.07 0.03; MTT=-0.25 0.04 MPP= 0.18 0.05; MRT= 0.34 0.10 MRP= 0.25 0.12; MTP= 5.77 0.03 PRINCIPAL AXES: 1.(T) VAL= 5.77;PLG= 4;AZM=314 2.(N) 0.04; 86; 124 3.(P) -5.81; 1; 224 BEST DOUBLE COUPLE:M0=5.8*10**25 NP1:STRIKE=359;DIP=87;SLIP= 178 NP2:STRIKE= 89;DIP=88;SLIP= 3 #####------ #########---------- T ##########----------- # ##########------------- ###############-------------- ################--------------- ################--------------- #################---------------- #################---------------- -----------------################ -----------------################ ----------------############### ----------------############### ---------------############## - ----------############# P ----------########### ----------######### ------#####

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: BW06 CMB HLID ISCO MA2 MAJO MOD NEW TPNV TUC WDC

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.)]

All observed and Greens function waveforms are corrected to instrument response to ground velocity in meters/sec for the passband of 0.01 - 5 Hz. Next tre traces were bandpass filtered by the application of the following high- and low-pass stages:

hp c 0.0100 2
lp c 0.0500 2

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   15.0   81.   83.    7.   6.46     0.544 0.157E-06     0.547     0.741 0.142E-06   3.5

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