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.)]
2007/04/12 18:24:47 -61.85 160.66 28
The following compares this source inversion to the USGS Rapid Moment Tensor Solution and to the Harvard CMT solutions, if they are available.
SLU Moment Tensor Solution
2007/04/12 18:24:47
Best Fitting Double Couple
Mo = 2.11e+25 dyne-cm
Mw = 6.15
Z = 220 km
Plane Strike Dip Rake
NP1 130 90 30
NP2 40 60 180
Principal Axes:
Axis Value Plunge Azimuth
T 2.11e+25 21 359
N 0.00e+00 60 130
P -2.11e+25 21 261
Moment Tensor: (dyne-cm)
Component Value
Mxx 1.80e+25
Mxy -3.18e+24
Mxz 8.10e+24
Myy -1.80e+25
Myz 6.79e+24
Mzz 2.57e+17
##### ######
######### T ##########
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Harvard Convention
Moment Tensor:
R T F
2.57e+17 8.10e+24 -6.79e+24
8.10e+24 1.80e+25 3.18e+24
-6.79e+24 3.18e+24 -1.80e+25
|
07/04/12 18:24:47.78
BALLENY ISLANDS REGION
Epicenter: -61.846 160.663
MW 6.0
USGS MOMENT TENSOR SOLUTION
Depth 28 No. of sta: 8
Moment Tensor; Scale 10**18 Nm
Mrr= 0.02 Mtt= 1.30
Mpp=-1.32 Mrt= 0.18
Mrp=-0.27 Mtp=-0.04
Principal axes:
T Val= 1.33 Plg= 8 Azm= 2
N 0.04 76 127
P -1.37 11 270
Best Double Couple:Mo=1.3*10**18
NP1:Strike= 46 Dip=77 Slip=-178
NP2: 316 88 -13
## ##
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|
April 12, 2007, BALLENY ISLANDS REGION, MW=6.0
Goran Ekstrom
CENTROID-MOMENT-TENSOR SOLUTION
GCMT EVENT: C200704121824A
DATA: IU II CU IC
L.P.BODY WAVES: 78S, 151C, T= 40
MANTLE WAVES: 66S, 99C, T=125
SURFACE WAVES: 71S, 144C, T= 50
TIMESTAMP: Q-20070412231442
CENTROID LOCATION:
ORIGIN TIME: 18:24:53.6 0.1
LAT:61.73S 0.01;LON:161.19E 0.01
DEP: 12.0 FIX;TRIANG HDUR: 2.4
MOMENT TENSOR: SCALE 10**25 D-CM
RR= 0.030 0.008; TT= 1.140 0.008
PP=-1.170 0.009; RT=-0.187 0.021
RP= 0.055 0.023; TP=-0.226 0.008
PRINCIPAL AXES:
1.(T) VAL= 1.193;PLG= 9;AZM=186
2.(N) 0.000; 80; 355
3.(P) -1.193; 2; 95
BEST DBLE.COUPLE:M0= 1.19*10**25
NP1: STRIKE=230;DIP=82;SLIP= 175
NP2: STRIKE=321;DIP=85;SLIP= 8
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|
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.
--------------------------------------------------------
General region : 2007bcbm SOUTHERN EAST PACIFIC RIS
surface waves (3.0,3.5,7,7.5 mHz)
Stations used : CCM HKT KIP NNA PMSA SDV SJG TUC
Origin time: 2007 103 18 24 19
Original location (lat,lon,depth) : -35.0000 -108.800 10
Moment tensor (x1.e26 dyncm) :
Mrr : 0.015622 Mtt : 0.076702
Mff : -0.092324 Mrt : 0.167017
Mrf : 0.089501 Mtf : -0.147936
T-axis: moment= 0.229 plunge= 32.790 azimuth= 15.346
N-axis: moment= 0.046 plunge= 41.827 azimuth= 250.139
P-axis: moment= -0.275 plunge= 30.786 azimuth= 127.916
best double couple: Mo= 0.252(x1.e26 dyncm) Mw=6.2 tau= 3.5
nodal planes (strike/dip/slip): 162.56/ 41.85/ 1.80 71.22/ 88.80/131.84
Centroid location : -34.965 -107.735 10.000
Centroid time : 20.593
Variance reduction (%) : 20
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|
The following broadband stations passed the QC and were used for the source inversion. AFI BBOO CHTO CTAO EIDS FITZ GUMO HNR KIP MBWA NNA NWAO POHA RPN WRAB
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 grid search, the observed traces and Green's functions are read in an cut using the following commands
Phase Gsac Command Comment P cut A -30 A CUTH = 95+0.3*DEPTH SH cut T1 -60 T1 CUTH = 95+0.6*DEPTH SV cut T0 -60 T0 CUTH = 95+0.6*DEPTH where the 95 is a maximum filter duration, DEPTH is in km, and the CUTH in secThe 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 0.0100 2 lp c 0.0400 2 int br c 0.12 0.2 n 4 p 2The 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.
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
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 270.0 124. 69. 49. 6.33 0.414 0.168E-05 0.465 0.649 0.715E-06 47.9
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
|
| 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. |
| 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 |
|
| 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. |
| SV-wave R 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. |
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 grid search, the observed traces and Green's functions are read in an cut using the following commands
Phase Gsac Command Comment P cut A -30 A CUTH = 95+0.3*DEPTH SH cut T1 -60 T1 CUTH = 95+0.6*DEPTH SV cut T0 -60 T0 CUTH = 95+0.6*DEPTH where the 95 is a maximum filter duration, DEPTH is in km, and the CUTH in secThe 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 0.0100 2 lp c 0.0400 2 int br c 0.12 0.2 n 4 p 2The 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.
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
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
WVFGRD96 220.0 130 90 30 6.15 0.4647
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
|
| 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. |
| 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 |
|
| 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. |
| SV-wave R 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. |
Starting Processing : Fri Apr 13 16:33:32 UTC 2007 Starting Processing : Fri Apr 13 16:33:32 UTC 2007 Starting stareq for response: Fri Apr 13 16:39:24 UTC 2007 Starting deconvolution : Fri Apr 13 16:41:49 UTC 2007 Starting trace rotation : Fri Apr 13 16:42:52 UTC 2007 Starting distance selection : Fri Apr 13 16:43:08 UTC 2007 Starting trace QC : Fri Apr 13 16:43:12 UTC 2007