Location

2006/08/26 23:40:44 51.42 -179.46 24

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	GLOBAL CMT
Mw=5.5 2006/08/26 23:40:44 EVID: LAT: 51.42N, LON: 179.46W, DEPTH: 25 Mw: 5.5, mb: 0.0, Ms: 0.0 Mo= 0.225E+25 (dyne-cm) No. of Stations: 20, GAP: 219 Error (clvd/dc)*100= 40.91 Bandpass: 12 - 60 sec Nodal plane parameters strike dip rake NP1: 85 82 84 NP2: 301 10 125 --------------- -#################--- -#######################--- -###########################--- ############# ###############-- ############## T ################-- ############### #################-- #####################################-- ######################################- ######################################- #################################-----# -####################-----------------# --------------------------------------# --------------------------------------# ------------------------------------- ----------------------------------- --------------- --------------- -------------- P -------------- ------------ ------------ --------------------- --------------- Stat Dist Az Misfit Stat Dist Az Misfit AHID 45 72 0.62 ANTO 84 335 0.30 BMO 40 73 0.84 BOZ 43 69 0.83 BR13 84 334 0.25 BW06 46 71 0.56 DUG 46 76 0.63 EGMT 43 65 1.16 ELK 44 77 0.83 HAWA 38 73 85.75 HKT 63 74 0.81 HLID 43 73 0.85 HWUT 46 74 0.56 JCT 60 77 0.71 KONO 69 355 0.77 OBN 69 338 0.19 TLY 45 302 0.46 TUC 52 83 0.99 WALA 40 66 1.01 YAK 29 311 0.45 Misfit > 1 heavily downweighted	06/08/26 23:40:44.10 ANDREANOF ISLANDS, ALEUTIAN IS. Epicenter: 51.419 -179.464 MW 5.6 USGS MOMENT TENSOR SOLUTION Depth 24 No. of sta: 60 Moment Tensor; Scale 10**17 Nm Mrr= 0.48 Mtt=-0.47 Mpp=-0.02 Mrt= 3.38 Mrp= 0.33 Mtp= 0.16 Principal axes: T Val= 3.46 Plg=49 Azm=351 N -0.05 3 85 P -3.41 41 178 Best Double Couple:Mo=3.4*10**17 NP1:Strike=306 Dip= 5 Slip= 131 NP2: 85 86 87 ------- -##############-- ####################- ########################- ############ #############- ############# T ##############- ############# ############### ################################- ################################# #######################---------- --------------------------------- --------------------------------- ------------------------------- -------------- -------------- ------------- P ------------- ----------- ----------- --------------------- ----------------- -------	August 26, 2006, ANDREANOF ISLANDS, ALEUTIAN IS., MW=5.7 Goran Ekstrom CENTROID, MOMENT TENSOR SOLUTION HARVARD EVENT-FILE NAME C082606A DATA USED: GSN L.P. BODY WAVES: 57S,118C, T= 40 SURFACE WAVES: 69S,140C, T= 50 CENTROID LOCATION: ORIGIN TIME 23:40:42.0 0.2 LAT 51.23N 0.01;LON 179.44W 0.02 DEP 24.3 1.2;HALF-DURATION 1.8 MOMENT TENSOR; SCALE 10**24 D-CM MRR= 1.64 0.06; MTT=-1.81 0.05 MPP= 0.16 0.04; MRT= 3.43 0.19 MRP= 0.24 0.07; MTP= 0.34 0.04 PRINCIPAL AXES: 1.(T) VAL= 3.80;PLG=58;AZM=349 2.(N) 0.13; 6; 89 3.(P) -3.93; 32; 183 BEST DOUBLE COUPLE:M0=3.9*10**24 NP1:STRIKE=294;DIP=15;SLIP= 116 NP2:STRIKE= 87;DIP=77;SLIP= 83 ----------- ----#########------ --#################---- -#######################--- ############ ############-- ############# T #############-- ############# ##############- ###############################-- ################################- #############################---# -------------#------------------# ------------------------------- ------------------------------- ----------------------------- ----------- ------------- --------- P ----------- ------- --------- -----------

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: AHID ANTO BMO BOZ BR131 BW06 DUG EGMT ELK HAWA HKT HLID HWUT JCT KONO OBN TLY TUC WALA YAK

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
int

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   85.   82.   84.   5.53     0.328 0.774E-07     0.452     0.578 0.516E-07  40.9

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

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.

Detailed Waveform Comparison

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.

Inversion Details