Location

2006/04/19 20:36:46 2.72 93.13 10

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=6.2 2006/04/19 20:36:46 EVID: LAT: 2.72N, LON: 93.13E, DEPTH: 10 Mw: 6.2, mb: 0.0, Ms: 0.0 Mo= 0.196E+26 (dyne-cm) No. of Stations: 67, GAP: 91 Error (clvd/dc)*100= 9.82 Bandpass: 12 - 60 sec Nodal plane parameters strike dip rake NP1: 178 82 -18 NP2: 270 72 -171 ------######### ---------############ ------------############### --------------################# ---------------################## ---------------#################### ----------------##################### -----------------###################### ----------#######-----------########### ---##############------------------#### ##################--------------------- ##################--------------------- ##################--------------------- ##################--------------------- #################-------------------- ################------------ ---- ## ##########------------ P --- # T ###########----------- -- ###########-------------- ##########----------- ########------- Stat Dist Az Misfit Stat Dist Az Misfit AAK 43 339 0.49 AML 42 338 0.51 ANTO 65 312 4.13 AQU 80 312 3.17 ARU 60 338 1.52 BFO 84 318 2.01 BILL 81 21 1.23 BJT 42 26 0.61 BNI 85 314 2.05 BOSA 72 238 0.64 BRVK 53 343 0.92 CASY 69 172 0.56 CHM 43 340 0.52 CSS 63 307 4.93 DAV 32 81 0.84 DIVS 76 314 3.98 DPC 79 320 1.90 EIL 61 302 0.92 EKS2 43 339 0.55 ENH 31 27 2.21 GNI 57 317 3.52 GRFO 82 319 1.95 GUMO 52 74 1.00 HGN 86 320 2.32 HIA 51 21 1.39 IBBN 85 322 1.92 ISP 66 310 3.57 KHC 81 319 0.87 KIV 60 320 3.16 KONO 84 329 1.71 KSDI 61 306 1.96 KURK 49 347 1.03 KWP 75 320 1.57 KZA 42 340 0.41 LBTB 70 242 0.59 LSZ 66 252 0.67 MA2 71 26 1.18 MALT 61 312 3.02 MBAR 62 267 1.52 MORC 78 320 1.81 MSEY 38 259 2.08 NACB 34 49 0.57 OBN 69 329 1.79 PSZ 76 318 2.48 RGN 81 324 1.67 RUE 81 322 1.84 SSB 87 315 2.27 STU 83 318 2.21 SUW 76 325 1.76 TATO 35 48 0.74 TIRR 70 316 3.24 TIXI 72 11 1.17 TKM2 42 341 0.44 TLY 49 8 1.32 TRI 80 315 2.18 TUE 83 316 2.32 UCH 42 339 0.45 ULHL 42 341 0.45 USP 43 340 0.44 VLC 82 313 2.81 VOS 53 343 1.22 VSU 75 330 1.67 VTS 73 313 4.36 WLF 85 319 1.83 YHNB 34 48 0.73 YSS 61 36 0.50 YULB 34 50 0.82 Misfit > 1 heavily downweighted	OFF W COAST OF NORTHERN SUMATRA Epicenter: 2.722 93.133 MW 6.0 USGS MOMENT TENSOR SOLUTION Depth 25 No. of sta: 21 Moment Tensor; Scale 10**18 Nm Mrr= 0.18 Mtt=-0.95 Mff= 0.77 Mrt=-0.02 Mrf=-0.58 Mtf=-1.01 Principal axes: T Val= 1.45 Plg=22 Azm= 67 N 0.01 65 222 P -1.46 9 333 Best Double Couple:Mo=1.5*10**18 NP1:Strike=108 Dip=67 Slip= 170 NP2: 202 81 23 ------- -----------### -- P ----------###### ---- ---------######### -----------------############ -----------------######### ## ----------------########## T ## ##--------------########### ### ####-----------################## #######--------################## ##########----################### #############-################### ############--------########### ###########-------------------- ##########------------------- #######------------------ #####---------------- ##--------------- -------	April 19, 2006, OFF W COAST OF NORTHERN SUMATRA, MW=6.2 Natasha Maternovskaya CENTROID, MOMENT TENSOR SOLUTION HARVARD EVENT-FILE NAME C041906A DATA USED: GSN L.P. BODY WAVES: 76S,181C, T= 40 MANTLE WAVES: 74S,136C, T=125 CENTROID LOCATION: ORIGIN TIME 20:36:50.4 0.1 LAT 2.85N 0.01;LON 93.19E 0.01 DEP 15.5 1.2;HALF-DURATION 3.1 MOMENT TENSOR; SCALE 10**25 D-CM MRR=-0.34 0.02; MTT=-1.28 0.02 MPP= 1.61 0.02; MRT=-0.08 0.04 MRP=-0.15 0.05; MTP=-1.72 0.02 PRINCIPAL AXES: 1.(T) VAL= 2.42;PLG= 2;AZM= 65 2.(N) -0.33; 85; 180 3.(P) -2.09; 5; 335 BEST DOUBLE COUPLE:M0=2.3*10**25 NP1:STRIKE=110;DIP=85;SLIP=-178 NP2:STRIKE= 20;DIP=88;SLIP= -5 ----------- - P -----------#### --- ----------####### -----------------########## ------------------########## ------------------########### T ##----------------########### #######-----------############### ###########------################ ################-################ ################-----############ ##############------------##### #############------------------ ############----------------- ##########----------------- #######---------------- #####-------------- -----------

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: AAK AML ANTO AQU ARU BFO BILL BJT BNI BOSA BRVK CASY CHM CSS DAV DIVS DPC EIL EKS2 ENH GNI GRFO GUMO HGN HIA IBBN ISP KHC KIV KONO KSDI KURK KWP KZA LBTB LSZ MA2 MALT MBAR MORC MSEY NACB OBN PSZ RGN RUE SSB STU SUW TATO TIRR TIXI TKM2 TLY TRI TUE UCH ULHL USP VLC VOS VSU VTS WLF YHNB YSS YULB

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

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   10.0  178.   82.  -18.   6.16     0.208 0.452E-06     0.285     0.468 0.356E-06   9.8

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