Location

2006/02/04 09:17:04 0.99 -90.56 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 Moment Tensor Solution 2006/02/04 09:17:04 Best Fitting Double Couple Mo = 5.82e+24 dyne-cm Mw = 5.81 Z = 15 km Plane Strike Dip Rake NP1 344 80 20 NP2 250 70 169 Principal Axes: Axis Value Plunge Azimuth T 5.82e+24 21 209 N 0.00e+00 68 9 P -5.82e+24 7 116 Moment Tensor: (dyne-cm) Component Value Mxx 2.80e+24 Mxy 4.39e+24 Mxz -1.43e+24 Myy -3.48e+24 Myz -1.54e+24 Mzz 6.81e+23 --############ -------############### -----------################# -------------################# ----------------################## -----------------################### -------------------################### ---------------------###---------------- ------------------###------------------- ---------------########------------------- -----------############------------------- --------################------------------ -----###################------------------ --######################---------------- -#######################------------ - ########################----------- P #######################----------- ######## ###########------------ ###### T ###########---------- ##### ############-------- #################----- #############- Harvard Convention Moment Tensor: R T F 6.81e+23 -1.43e+24 1.54e+24 -1.43e+24 2.80e+24 -4.39e+24 1.54e+24 -4.39e+24 -3.48e+24

AUTOMATIC moment tensor based on an AUTOMATIC NEIC location Mw=5.5 GALAPAGOS ISLANDS REGION 2006/02/04 09:17: 4.24 EVID: ITAF LAT: 1.01N, LON: 90.62W, DEPTH: 10 Mw: 5.5, mb: 6.0, Ms: 6.0 Mo= 0.197E+25 (dyne-cm) No. of Stations: 5, GAP: 205 Error (clvd/dc)*100= 29.25 Nodal plane parameters strike dip rake NP1: 133 84 264 NP2: 359 9 -44 ---------# ------------------## ------------------------## ----------------------------## ###----------------------------# #####----------------------------# ########---------------------------# ##########--------------------------## ############-------------------------# ###############-----------------------## #################---------------------## ###################-------------------## #####################-----------------## ######################---------------# ########################------------## #########################----------# ###########################------# ############################---# ############################-- ########################-- ##################-- #########- Stat Dist Az Misfit Stat Dist Az Misfit CPUP 42 132 0.79 LRAL 32 5 0.93 PLCA 45 158 2.23 RCBR 55 97 1.01 WVT 35 3 0.82 Median of misfit: 0.93 Average misfit: 1.16

Event name: 020406A Region name: GALAPAGOS ISLANDS REGION Date (y/m/d): 2006/2/4 ----########## ---------############# ------------################ -------------################ P --------------################# - --------------################## --------------------################## ---------------------################### ---------------------################### -----------------------###############---- -----------------------#####-------------- -----------------######------------------- ------##################------------------ #######################----------------- #######################----------------- ######################---------------- ######################-------------- #####################------------- ## ##############----------- # T ##############---------- ##############------- ###########--- Information on data used in inversion Wave nsta nrec cutoff Body 72 154 40 Mantle 0 0 0 Surface 75 164 50 Timing and location information hr min sec lat lon depth mb Ms PDE 9 17 3.00 1.04 -90.52 10.0 5.9 5.9 CMT 9 17 7.80 1.08 -90.73 12.0 Error 0.10 0.01 0.01 0.0 Assumed half duration: 2.2 Mechanism information Exponent for moment tensor: 24 units: dyne-cm Mrr Mtt Mpp Mrt Mrp Mtp CMT -0.680 3.160 -2.480 -1.270 -0.260 -7.530 Error 0.060 0.060 0.080 0.150 0.180 0.060 Mw = 5.9 Scalar Moment = 8.15e+24 Fault plane: strike=350 dip=81 slip=-1 Fault plane: strike=80 dip=89 slip=-171 Eigenvector: eigenvalue: 8.47 plunge: 6 azimuth: 214 Eigenvector: eigenvalue: -0.65 plunge: 81 azimuth: 88 Eigenvector: eigenvalue: -7.83 plunge: 8 azimuth: 305

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: AAM ACSO BBSR BLA CBN CPUP ERPA FDF JCT LBNH LRAL LVC MCWV NHSC OXF PLCA RCBR TZTN WVT

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   20.0  347.   87.   16.   5.82     0.349 0.223E-06     0.389     0.591 0.133E-06  12.5

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