Location

2006/06/27 13:03:12 15.04 -94.05 30

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	HARVARD CMT
Mw=5.8 2006/06/27 13:03:12 EVID: LAT: 15.04N, LON: 94.05W, DEPTH: 20 Mw: 5.8, mb: 0.0, Ms: 0.0 Mo= 0.624E+25 (dyne-cm) No. of Stations: 11, GAP: 264 Error (clvd/dc)*100= 30.97 Bandpass: 12 - 60 sec Nodal plane parameters strike dip rake NP1: 135 59 127 NP2: 260 47 46 --------------- --------------------- --------------------------- #------------------------------ ###------------------------------ ####--------#################------ #####---##########################--- #####################################-- ####----############################### ###------############################## ##--------################ ########## #----------############### T ########## -------------############# ########## --------------######################### ---------------###################### -----------------################## -------------------############## ---------------------########## --------------------------- --- --------------- P ------------ Stat Dist Az Misfit Stat Dist Az Misfit BMR 58 333 0.36 BPAW 62 335 0.42 DSB 76 38 0.75 FFC 40 352 0.38 ISA 29 317 0.57 KBS 78 10 0.58 PAB 80 51 0.47 PSZ 94 38 0.48 Q03C 34 318 0.86 SAW 60 333 0.84 V03C 32 315 0.74 Misfit > 1 heavily downweighted	OFFSHORE CHIAPAS, MEXICO Epicenter: 15.039 -94.053 MW 5.8 USGS MOMENT TENSOR SOLUTION Depth 11 No. of sta: 40 Moment Tensor; Scale 10**17 Nm Mrr= 2.53 Mtt=-3.12 Mpp= 0.58 Mrt= 4.72 Mrp=-1.74 Mtp=-0.56 Principal axes: T Val= 5.81 Plg=56 Azm= 35 N 0.00 15 283 P -5.81 30 184 Best Double Couple:Mo=5.8*10**17 NP1:Strike=237 Dip=20 Slip= 43 NP2: 106 77 105 ------- ----------------- -------############-- -----###################- -----######################## ----############## ########## ---############### T ########## ##-################ ########### ##---############################ ##-------######################## #-------------################### #--------------------############ ------------------------------- #------------------------------ ------------ -------------- ---------- P ------------ -------- ---------- ----------------- -------	Subject: quick CMT: 06/27/06, 13:03:12.0, OFFSHORE CHIAPAS, MEXICO, MW=5.8 Here is the solution for the recent event. June 27, 2006, OFFSHORE CHIAPAS, MEXICO, MW=5.8 Natasha Maternovskaya CENTROID, MOMENT TENSOR SOLUTION HARVARD EVENT-FILE NAME C062706E DATA USED: GSN L.P. BODY WAVES: 64S,140C, T= 40 SURFACE WAVES: 66S,165C, T= 50 CENTROID LOCATION: ORIGIN TIME 13:03:13.3 0.1 LAT 14.95N 0.01;LON 94.53W 0.01 DEP 12.0 FIX;HALF-DURATION 2.0 MOMENT TENSOR; SCALE 10**24 D-CM MRR= 4.00 0.05; MTT=-2.46 0.05 MPP=-1.53 0.06; MRT= 3.95 0.14 MRP=-3.42 0.15; MTP= 1.90 0.04 PRINCIPAL AXES: 1.(T) VAL= 6.59;PLG=64;AZM= 43 2.(N) -0.04; 1; 310 3.(P) -6.54; 26; 219 BEST DOUBLE COUPLE:M0=6.6*10**24 NP1:STRIKE=306;DIP=19;SLIP= 86 NP2:STRIKE=130;DIP=71;SLIP= 91 ----------- ---#########------- -#################----- #######################---- ---######################---- -----############# #######--- ------############ T ########-- --------########### #########-- ----------#####################-- ------------###################-- --------------##################- ---------------###############- ------------------############- ----- ------------########- ---- P ----------------#### -- ------------------ ------------------- -----------

Deviatoric Moment Tensor Solution

The following broadband stations were used for the source inversion: BMR BPAW DSB FFC ISA KBS PAB PSZ Q03C SAW V03C

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   20.0  135.   59.  127.   5.83     0.378 0.248E-06     0.408     0.615 0.209E-06  31.0

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