Moment Tensor 20070429124158

Location

2007/04/29 12:41:58 52.08 -179.98 123

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 POLET

SLU Moment Tensor Solution 2007/04/29 12:41:58 Best Fitting Double Couple Mo = 2.04e+25 dyne-cm Mw = 6.14 Z = 120 km Plane Strike Dip Rake NP1 329 77 -98 NP2 180 15 -60 Principal Axes: Axis Value Plunge Azimuth T 2.04e+25 32 65 N 0.00e+00 7 331 P -2.04e+25 57 229 Moment Tensor: (dyne-cm) Component Value Mxx 1.29e+17 Mxy 2.64e+24 Mxz 9.86e+24 Myy 8.84e+24 Myz 1.53e+25 Mzz -8.84e+24 --############ #-#################### ###---###################### ##-------##################### ###----------##################### ###------------##################### ###--------------############# ##### ###-----------------########### T ###### ###------------------########## ###### ###--------------------################### ###---------------------################## ###----------------------################# ###----------- ---------################ ###---------- P ----------############## ###---------- -----------############# ###------------------------########### ###------------------------######### ###-----------------------######## ##-----------------------##### ###---------------------#### ##-------------------- ##------------ Harvard Convention Moment Tensor: R T F -8.84e+24 9.86e+24 -1.53e+25 9.86e+24 1.29e+17 -2.64e+24 -1.53e+25 -2.64e+24 8.84e+24

07/04/29 12:41:58.23 ANDREANOF ISLANDS, ALEUTIAN IS. Epicenter: 52.081 -179.979 MW 6.2 USGS MOMENT TENSOR SOLUTION Depth 117 No. of sta: 93 Moment Tensor; Scale 10**18 Nm Mrr=-1.10 Mtt=-0.83 Mpp= 1.93 Mrt= 0.87 Mrp=-1.87 Mtp=-0.73 Principal axes: T Val= 3.10 Plg=26 Azm= 73 N -0.91 14 336 P -2.19 60 220 Best Double Couple:Mo=2.6*10**18 NP1:Strike=193 Dip=23 Slip= -51 NP2: 332 72 -105 ------- #-----########### ##################### #####----################ #####-------################# #####----------################ ####------------########## ## ####--------------######### T ### ####---------------######## ### ####----------------############# ####------- -------############ ####------- P --------########### ###------- ---------######### ####------------------######### ####------------------####### ###-----------------##### ##----------------### ##--------------- -------

USGS research CMT: maintained and developed by Jascha Polet at UC Santa Barbara. This is a research system and solutions are *not* official USGS earthquake magnitudes. AUTOMATIC solution, not reviewed by a seismologist -------------------------------------------------- General region : 2007bta3 ANDREANOF ISLANDS, ALEUTI surface waves (3.0,3.5,7,7.5 mHz) Stations used : COR FFC INCN KIP MAJO TIXI YAK Origin time: 2007 119 12 41 58 Original location (lat,lon,depth) : 52.1000 -180.000 123 Moment tensor (x1.e26 dyncm) : Mrr : -0.125836 Mtt : 0.010471 Mff : 0.115365 Mrt : 0.067847 Mrf : -0.165560 Mtf : -0.040821 T-axis: moment= 0.221 plunge= 27.248 azimuth= 69.686 N-axis: moment= -0.003 plunge= 1.641 azimuth= 338.841 P-axis: moment= -0.218 plunge= 62.694 azimuth= 245.659 best double couple: Mo= 0.220(x1.e26 dyncm) Mw=6.2 tau= 3.3 nodal planes (strike/dip/slip): 338.32/ 72.27/-91.72 163.96/ 17.81/-84.63 Centroid location : 51.732 -179.905 119.359 Centroid time : 1.834 Variance reduction (%) : 56 *********** ****o ---------**** ***o ooo------------*** **oo oo--------------** **oo oo--------------** * oo oo---------------* * oo oo---------------* ** o o----------T---** * o oo--------------* ** oo oo-------------** ** oo + oo------------** ** o P o------------** * o oo-----------* ** oo o----------** * oo oo---------* * oo o--------* ** ooo o------** ** ooo o ----** *** ooo o -*** ****ooooo **** *********** 0- 30- 60- 90- 120- 150- 180- 210- 240- 270- 300- 330- z-comp: 0 1 0 1 1 0 0 1 1 1 0 0 r-comp: 0 0 0 0 0 0 1 1 1 1 0 0 t-comp: 0 0 0 0 1 0 1 1 1 1 0 0 Total number of traces used = 15 number of runs = 6 starttime = Sun Apr 29 07:00:56 MDT 2007 endtime = Sun Apr 29 07:12:31 MDT 2007 inversion time = Sun Apr 29 07:12:29 MDT 2007 - Sun Apr 29 07:12:31 MDT 2007 Solution produced by inversion of channels with var red > 2%

Data set

The following broadband stations passed the QC and were used for the source inversion. AAK AAM AFI AGMN ANMO ANTO ARU BBSR BCIP BFO BLA BRAL BRVK CCM CHTO CMB COR COWI CTAO DAV DGMT DUG DWPF ECSD EGMT ESK EYMN FFC GRFO GUMO HAWA HKT HLID HNR INCN ISCO JCT JFWS KBL KBS KEV KIP KIV KSU1 KURK KVTX MAJO MVCO NEW NLWA OBN PAB PALK PFO PKME POHA RAR RSSD SCIA SFJD SJG SNZO SSPA TARA TATO TEIG TGUH TLY TUC TZTN ULN WMOK WRAB WUAZ WVOR WVT

Deviatoric Moment Tensor Inversion

All observed and Greens function waveforms are corrected to instrument response to ground velocity in meters/sec for the passband of 0.004 - 5 Hz. The traces were then lowpass filtered at 0.25 Hz and interpolated to a sample rate of 1 second.

For the deviatoric moment tensor inversion, the observed traces and Green's functions are read in an cut using the following commands

Processing parameters

#####
#	Driver script for the teleseismic waveform inversion
#
#	The depth HS must be of the form 0010 for a depth of 1.0 km
#       of 6700 for a depth of 670.0 km
#
#	The Filter_Band is an integer with the following meansing
#
#	FILTER_BAND	1/FH	1/FL
#	1		60	12	for Mw < 6.4
#	2		100	20	6.4 =< Mw < 6.8 
#	3		120	40	6.8 =< Mw < 7.2 
#	4		143	80	7.2 =< Mw < 9.3 
#####
#	Source duration - halfwidth of triangular function
#	this filters only the Green functions
#
#	halfwidth = 1.05 * 10-8 * M0^1/3 (M0 is dyne-cm)
#
#	MW	   half-width (sec)
#	5.0         0.75
#	6.0         2.45
#	7.0         7.7
#	8.0        24.5
#	9.0        74.3
#                       0.5*(MW - 9)
#  or half-width=74.3*10
#  or echo 5.83 |  awk '{print 74.3*exp(0.5*log(10.0)*(0350 - 9.0)) }'
#####
#  Processing window for P (use SAC variable A for P arrival
#  	Start   A  - 30
#  	End     A  + 2*HALFWIDTH + 0.03*HS + 30 + 1/FH
#  Processing window for SH (use SAC variable T0 for SH arrival
#  	Start   T0 - 60
#  	End     T0 + 2*HALFWIDTH + 0.06*HS + 30 + 1/FH
#  Processing window for SV (use SAC variable T1 for SV arrival
#  	Start   T1 - 60
#  	End     T1 + 2*HALFWIDTH + 0.06*HS + 30 + 1/FH
#	
#	The term involving HS serves to include the depth phases and
#	to exclude the PP or SS at most distanace
#####

The cut windows attempt to include the P, pP, sP, pS, S and sS arrivals. However, oen must be very careful about the fact that PP may be included in some distance ranges.

The waveforms are then bandpass filtered by the application of the following high- and low-pass stages (an optional microseism filter):

hp c 0.0167 2
lp c 0.0833 2
int
br c 0.12 0.25 n 4 p 2

The traces were next integrated to ground displacment in meters. Finally the observed data are interpolated to ahve the same sampling at the Green's functions.
NOTE: this was done for speed. The proper sequence is to read traces, filter and then cut - gsac will be modified to introduce a command CUTWR to define the cut upon a write.

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

The map displays the distribution of stations used for this source inversion.

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.)]

For this data set the favored solution is

WVFMTD96   35.0  286.   86. -148.   5.82     0.289 0.116E-05     0.281     0.549 0.530E-06  67.6

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.

Detailed Waveform Comparison

P-wave Z component

Comparison of the observed traces (red) and solution predicted traces (blue) ordered in terms of increasing epicentral distance. Each pair of traces is annotated with the station name, epicentral distance in degrees, source to station azimuth in degrees. Each pair of traces is plotted with the same scale and the peak amplitudes are indicated at the lect of each trace. Finally the time shift between the P-wave first arrival picked and the the theoretical P-wave first arrival in the predicted trace is indicated, with a positive sign indicating that the predicted trace has been shifted to the right by the given number of seconds. 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.

SH-wave T component

SV-wave R component

Inversion Details

Output of wvfmtd96 for the best depth..

Grid Search

For the grid search, the observed traces and Green's functions are read in an cut using the following commands