Location

2006/05/03 15:26:35 -20.04 -174.23 16

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=7.8 2006/05/03 15:26:35 EVID: LAT: 20.04S, LON: 174.23W, DEPTH: 80 Mw: 7.8, mb: 0.0, Ms: 0.0 Mo= 0.519E+28 (dyne-cm) No. of Stations: 55, GAP: 52 Error (clvd/dc)*100= 44.38 Bandpass: 40 - 100 sec Nodal plane parameters strike dip rake NP1: 18 77 70 NP2: 257 23 146 --------------# -----------------#### ---------###########-###### ------################-----#### -----#################---------## ----###################-----------# ---#####################------------# ---#####################--------------# --######################--------------- -######## ###########---------------- -######## T ###########---------------- ######### ##########----------------- ######################----------------- #####################--------- ------ ###################---------- P ----- #################----------- ---- ###############------------------ #############------------------ ##########----------------- ######--------------- ##------------- Stat Dist Az Misfit Stat Dist Az Misfit 116A 79 49 0.96 A05A 82 31 2.59 ARMA 32 244 6.25 ATKA 71 0 0.30 BBOO 45 243 0.53 BC3 77 46 1.14 BILL 88 352 0.30 BJT 88 313 0.44 BLDU 62 245 0.52 BW06 86 41 1.38 C05A 82 32 2.42 CASY 65 205 0.39 CHTO 93 288 0.32 CTAO 37 262 0.25 D04A 81 32 2.89 D05A 81 33 2.46 EIDS 32 254 0.62 FITZ 56 261 0.41 FORT 52 246 25.24 HATC 77 38 2.45 HIA 90 323 0.36 I03A 78 34 3.13 KIP 44 21 1.20 KMBL 57 244 0.48 KSM 76 276 0.35 KUM 87 276 0.39 L09A 80 39 2.24 MAUI 44 24 2.06 MBWA 61 256 0.30 MCK 85 10 0.37 MIDW 48 356 0.39 NEW 84 34 2.34 NIKO 72 3 0.27 NNA 92 103 0.45 NWAO 61 242 0.29 PMG 38 280 0.25 POHA 43 25 2.11 PPLA 84 9 0.30 PTCN 40 105 0.82 QIZ 83 292 0.39 SBA 58 184 0.42 SNCC 74 45 1.34 STKA 41 244 0.28 TNA 85 2 0.28 TOO 39 234 12.65 TOV 75 44 1.30 TRQA 94 132 0.42 TUC 79 50 1.18 U05C 75 42 1.51 UNV 73 4 0.27 VNDA 58 185 0.41 W15A 80 47 0.98 WMOK 89 52 0.71 WRAB 48 260 0.31 YNG 35 238 0.30 Misfit > 1 heavily downweighted	Epicenter: -20.035 -174.227 MW 8.1 USGS MOMENT TENSOR SOLUTION Depth 5 No. of sta: 44 Moment Tensor; Scale 10**21 Nm Mrr= 0.16 Mtt=-0.46 Mff= 0.30 Mrt= 0.50 Mrf= 1.67 Mtf=-0.05 Principal axes: T Val= 1.94 Plg=44 Azm=281 N -0.36 9 19 P -1.58 44 118 Best Double Couple:Mo=1.8*10**21 NP1:Strike=290 Dip= 9 Slip=-180 NP2: 199 90 -81 ------- ---#########--### -##############----## -###############-------## -#################---------## ##################-----------## #################-------------# ####### ########--------------# ####### T #######---------------- ####### ######----------------- ################------- ------- ###############-------- P ------- ##############-------- ------ #############------------------ ###########------------------ #########---------------- ######--------------- ###-------------- -------	May 3, 2006, TONGA, MW=7.9 Natasha Maternovskaya Goran Ekstrom CENTROID, MOMENT TENSOR SOLUTION HARVARD EVENT-FILE NAME M050306A DATA USED: GSN MANTLE WAVES: 48S, 85C, T=150 CENTROID LOCATION: ORIGIN TIME 15:27: 8.7 0.5 LAT 20.33S 0.04;LON 174.03W 0.05 DEP 65.5 1.7;HALF-DURATION 24.6 MOMENT TENSOR; SCALE 10**28 D-CM MRR= 0.59 0.01; MTT=-0.17 0.01 MPP=-0.42 0.01; MRT= 0.11 0.02 MRP= 0.75 0.02; MTP=-0.28 0.01 PRINCIPAL AXES: 1.(T) VAL= 0.99;PLG=62;AZM=266 2.(N) -0.05; 12; 18 3.(P) -0.94; 26; 114 BEST DOUBLE COUPLE:M0=1.0*10**28 NP1:STRIKE=228;DIP=22;SLIP= 122 NP2:STRIKE= 14;DIP=72;SLIP= 78 ----------# ---------#####--### ------##########------# -----#############--------- ----###############---------- ----################----------- ---#################----------- ---##################------------ --####### #########------------ --####### T ########------------- --####### ########------ ---- -#################------- P --- -################-------- --- -###############------------- -#############------------- ###########------------ ########----------- ##---------

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: 116A A05A ARMA ATKA BBOO BC3 BILL BJT BLDU BW06 C05A CASY CHTO CTAO D04A D05A EIDS FITZ FORT HATC HIA I03A KIP KMBL KSM KUM L09A MAUI MBWA MCK MIDW NEW NIKO NNA NWAO PMG POHA PPLA PTCN QIZ SBA SNCC STKA TNA TOO TOV TRQA TUC U05C UNV VNDA W15A WMOK WRAB YNG

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 0.0083 2
lp c 0.0250 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   80.0   18.   77.   70.   7.78     0.534 0.587E-04     0.592     0.731 0.493E-04  44.4

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