Location

2006/07/07 07:26:12 -15.26 -173.60 35

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.

SLU	USGS	HARVARD CMT
Mw=5.9 2006/07/07 07:26:12 EVID: LAT: 15.26S, LON: 173.60W, DEPTH: 35 Mw: 5.9, mb: 0.0, Ms: 0.0 Mo= 0.717E+25 (dyne-cm) No. of Stations: 33, GAP: 115 Error (clvd/dc)*100= 34.18 Bandpass: 12 - 60 sec Nodal plane parameters strike dip rake NP1: 95 87 -83 NP2: 212 7 -153 ###-----------# ##------------------- ##------------------------- ##----------------------------- ##--------------- ------------- #----------------- P -------------- ##----------------- --------------- ##------------------------------------- #-------------------------------------- #-------------------------------------- -##########---------------------------- -###################################### -###################################### -###################################### -#################################### -############### ################ -############## T ############### -############# ############## -########################## ##################### ############### Stat Dist Az Misfit Stat Dist Az Misfit BBOO 48 239 0.61 BERG 79 14 0.37 BJT 85 313 0.71 CCM 93 51 0.44 COLA 82 10 0.42 CTAO 38 256 0.93 FFC 92 33 0.42 FITZ 58 257 0.84 FORT 55 242 7.41 FUR 74 44 0.44 HOPS 71 39 0.36 JCT 84 56 3.08 JRSC 71 41 0.35 KMBL 60 242 0.65 KOM 83 273 0.89 LDM 70 281 0.78 LTY 78 33 0.71 M10A 77 40 0.44 MBWA 63 253 0.80 MCK 81 10 0.34 N09A 76 40 0.45 PET 72 342 0.39 SBA 63 184 0.69 SDPT 71 7 0.38 SIUC 94 52 0.73 SPIA 72 1 0.44 TEIG 90 69 0.73 TRF 80 10 0.54 UNV 69 4 0.53 VNDA 63 185 0.68 WRAB 49 256 0.73 Y22C 80 50 0.48 YSS 73 330 0.50 Misfit > 1 heavily downweighted	06/07/07 07:26:12.31 TONGA Epicenter: -15.258 -173.605 MW 6.0 USGS MOMENT TENSOR SOLUTION Depth 34 No. of sta: 66 Moment Tensor; Scale 10**18 Nm Mrr= 0.05 Mtt=-0.09 Mpp= 0.04 Mrt=-1.06 Mrp= 0.27 Mtp= 0.03 Principal axes: T Val= 1.07 Plg=47 Azm=195 N 0.04 0 104 P -1.11 43 14 Best Double Couple:Mo=1.1*10**18 NP1:Strike= 96 Dip= 2 Slip= 81 NP2: 284 88 90 ------- ----------------- --------------------- ------------- --------- --------------- P ----------- ---------------- ------------ ------------------------------- ##------------------------------- ##########----------------------- ##################--------------- #########################-------- ###############################-- ############ ################ ############ T ################ -########## ##############- ######################### ##################### -###############- -------	July 7, 2006, TONGA, MW=6.0 Goran Ekstrom CENTROID, MOMENT TENSOR SOLUTION HARVARD EVENT-FILE NAME C070706A DATA USED: GSN L.P. BODY WAVES: 78S,178C, T= 40 MANTLE WAVES: 55S, 68C, T=125 CENTROID LOCATION: ORIGIN TIME 07:26:18.4 0.1 LAT 15.07S 0.01;LON 173.49W 0.01 DEP 57.7 1.6;HALF-DURATION 2.5 MOMENT TENSOR; SCALE 10**25 D-CM MRR=-0.09 0.01; MTT= 0.19 0.02 MPP=-0.10 0.02; MRT=-1.17 0.02 MRP= 0.11 0.01; MTP= 0.06 0.01 PRINCIPAL AXES: 1.(T) VAL= 1.23;PLG=42;AZM=182 2.(N) -0.08; 4; 276 3.(P) -1.14; 48; 10 BEST DOUBLE COUPLE:M0=1.2*10**25 NP1:STRIKE=222;DIP= 6;SLIP=-143 NP2:STRIKE= 96;DIP=87;SLIP= -86 ###-------# ##----------------# #---------------------- #------------- ---------- #-------------- P ----------- #--------------- ------------ ------------------------------- #-------------------------------- -###----------------------------- -##################-------------- -################################ ############################### -############################## ############# ############# -########### T ############ ########## ########## ################### ###########

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: BBOO BERG BJT CCM COLA CTAO FFC FITZ FORT FUR HOPS JCT JRSC KMBL KOM LDM LTY M10A MBWA MCK N09A PET SBA SDPT SIUC SPIA TEIG TRF UNV VNDA WRAB Y22C 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.)]

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 0.0167 2
lp c 0.0833 2
int

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   35.0   95.   87.  -83.   5.87     0.380 0.232E-06     0.470     0.617 0.142E-06  34.2

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