Location

2006/03/02 23:35:45 19.06 -63.95 17

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 Moment Tensor Solution 2006/03/02 23:35:45 Best Fitting Double Couple Mo = 3.24e+24 dyne-cm Mw = 5.64 Z = 25 km Plane Strike Dip Rake NP1 290 63 44 NP2 176 52 145 Principal Axes: Axis Value Plunge Azimuth T 3.24e+24 49 149 N 0.00e+00 40 315 P -3.24e+24 7 51 Moment Tensor: (dyne-cm) Component Value Mxx -2.73e+23 Mxy -2.17e+24 Mxz -1.60e+24 Myy -1.55e+24 Myz 5.41e+23 Mzz 1.82e+24 ####---------- ######---------------- ########-------------------- ########--------------------- #########---------------------- P ##########---------------------- - ###-------####------------------------ -----------###########------------------ ----------#################------------- -----------####################----------- -----------#######################-------- -----------#########################------ ------------##########################---- -----------###########################-- -----------############# ############- -----------############ T ############ -----------########### ########### ----------######################## ---------##################### ----------################## --------############## ------######## Harvard Convention Moment Tensor: R T F 1.82e+24 -1.60e+24 -5.41e+23 -1.60e+24 -2.73e+23 2.17e+24 -5.41e+23 2.17e+24 -1.55e+24

AUTOMATIC moment tensor based on an AUTOMATIC NEIC location Mw=5.3 LEEWARD ISLANDS 2006/03/02 23:32:18.28 EVID: JUB4 LAT: 19.02N, LON: 63.98W, DEPTH: 20 Mw: 5.3, mb: 5.8, Ms: 5.8 Mo= 0.105E+25 (dyne-cm) No. of Stations: 4, GAP: 143 Error (clvd/dc)*100= 18.94 Nodal plane parameters strike dip rake NP1: 186 31 136 NP2: 316 69 67 #####----- ######-------------- ######-------------------- ----##------------------------ ------###----------------------- ------#######--------------------- ------##########-------------------- ------##############------------------ ------################---------------- ------##################---------------- ------####################-------------- ------######################------------ ------#######################----------- -----########################--------- ------########################-------- -----#########################------ -----#########################---- -----########################--- -----########################- -----##################### ----################ -######### Stat Dist Az Misfit Stat Dist Az Misfit HKT 30 296 0.83 KIV 88 43 0.93 LPAZ 35 186 0.58 WMOK 34 304 0.95 Median of misfit: 0.88 Average misfit: 0.82

March 3, 2006, SOUTHERN MID-ATLANTIC RIDGE, MW=5.9 Meredith Nettles CENTROID, MOMENT TENSOR SOLUTION HARVARD EVENT-FILE NAME C030306A DATA USED: GSN L.P. BODY WAVES: 70S,162C, T= 40 SURFACE WAVES: 67S,152C, T= 50 CENTROID LOCATION: ORIGIN TIME 23:36:36.4 0.1 LAT 55.90S 0.01;LON 3.98W 0.01 DEP 14.7 0.7;HALF-DURATION 2.3 MOMENT TENSOR; SCALE 10**25 D-CM MRR=-0.03 0.01; MTT=-0.22 0.01 MPP= 0.25 0.01; MRT= 0.15 0.02 MRP=-0.07 0.02; MTP= 0.97 0.01 PRINCIPAL AXES: 1.(T) VAL= 1.01;PLG= 2;AZM=308 2.(N) 0.00; 80; 51 3.(P) -1.01; 9; 218 BEST DOUBLE COUPLE:M0=1.0*10**25 NP1:STRIKE=354;DIP=82;SLIP=-175 NP2:STRIKE=263;DIP=85;SLIP= -8 ####------- #########---------- ###########------------ T ############------------- ############-------------- ################--------------- #################-------------- ##################--------------- ###############---############### #####-------------############### ------------------############### ------------------############# ------------------############# -----------------############ --- ----------########### - P ----------######### ----------####### -------####

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: HKT KIV LPAZ

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.)]

The traces were next integrated to ground displacment in meters. Finally waveforms were cut from 30 seconds before to 140 seconds after the P arrival so that the direct P wave, pP and perhaps the sP are included.

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   25.0  290.   63.   44.   5.64     0.435 0.947E-07     0.435     0.666 0.947E-07  55.6

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.

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