Location

2007/10/31 03:04:54 37.43 -121.77 9.0 5.6 California

Arrival Times (from USGS)

Arrival time list

Felt Map

USGS Felt map for this earthquake

USGS Felt reports page for

Focal Mechanism

 SLU Moment Tensor Solution
 2007/10/31 03:04:54 37.43 -121.77 9.0 5.6 California
 
 Best Fitting Double Couple
    Mo = 2.09e+24 dyne-cm
    Mw = 5.48 
    Z  = 12 km
     Plane   Strike  Dip  Rake
      NP1      235    85   -15
      NP2      326    75   -175
 Principal Axes:
   Axis    Value   Plunge  Azimuth
     T   2.09e+24      7     282
     N   0.00e+00     74      37
     P  -2.09e+24     14     190



 Moment Tensor: (dyne-cm)
    Component  Value
       Mxx    -1.83e+24
       Mxy    -7.32e+23
       Mxz     5.37e+23
       Myy     1.92e+24
       Myz    -1.61e+23
       Mzz    -9.39e+22
                                                     
                                                     
                                                     
                                                     
                     --------------                  
                 ----------------------              
              #####-----------------------           
             ########----------------------          
           ############----------------------        
          ###############-----------------####       
         ##################-----------#########      
        ####################-------#############     
          ###################----###############     
        T ####################-##################    
          #################-----#################    
       #################---------################    
       ###############------------###############    
        ############---------------#############     
        #########-------------------############     
         ######----------------------##########      
          ###-------------------------########       
           ---------------------------#######        
             --------------------------####          
              ---------   -------------###           
                 ------ P -------------              
                     --   ---------                  
                                                     
                                                     
                                                     

 Harvard Convention
 Moment Tensor:
      R          T          F
 -9.39e+22   5.37e+23   1.61e+23 
  5.37e+23  -1.83e+24   7.32e+23 
  1.61e+23   7.32e+23   1.92e+24 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20071031030454/index.html
        

Preferred Solution

The preferred solution from an analysis of the surface-wave spectral amplitude radiation pattern, waveform inversion and first motion observations is

      STK = 235
      DIP = 85
     RAKE = -15
       MW = 5.48
       HS = 12

The surface-wave is preferred. Rake is least well determined.

Moment Tensor Comparison

The following compares this source inversion to others
SLU
GCMT
UCB
 SLU Moment Tensor Solution
 2007/10/31 03:04:54 37.43 -121.77 9.0 5.6 California
 
 Best Fitting Double Couple
    Mo = 2.09e+24 dyne-cm
    Mw = 5.48 
    Z  = 12 km
     Plane   Strike  Dip  Rake
      NP1      235    85   -15
      NP2      326    75   -175
 Principal Axes:
   Axis    Value   Plunge  Azimuth
     T   2.09e+24      7     282
     N   0.00e+00     74      37
     P  -2.09e+24     14     190



 Moment Tensor: (dyne-cm)
    Component  Value
       Mxx    -1.83e+24
       Mxy    -7.32e+23
       Mxz     5.37e+23
       Myy     1.92e+24
       Myz    -1.61e+23
       Mzz    -9.39e+22
                                                     
                                                     
                                                     
                                                     
                     --------------                  
                 ----------------------              
              #####-----------------------           
             ########----------------------          
           ############----------------------        
          ###############-----------------####       
         ##################-----------#########      
        ####################-------#############     
          ###################----###############     
        T ####################-##################    
          #################-----#################    
       #################---------################    
       ###############------------###############    
        ############---------------#############     
        #########-------------------############     
         ######----------------------##########      
          ###-------------------------########       
           ---------------------------#######        
             --------------------------####          
              ---------   -------------###           
                 ------ P -------------              
                     --   ---------                  
                                                     
                                                     
                                                     

 Harvard Convention
 Moment Tensor:
      R          T          F
 -9.39e+22   5.37e+23   1.61e+23 
  5.37e+23  -1.83e+24   7.32e+23 
  1.61e+23   7.32e+23   1.92e+24 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20071031030454/index.html
	
October 31, 2007, SAN FRANCISCO BAY AREA, CAL, MW=5.6

Goran Ekstrom
Meredith Nettles

CENTROID-MOMENT-TENSOR  SOLUTION
GCMT EVENT:     C200710310304A  
DATA: IU II CU IC GE 
L.P.BODY WAVES: 49S,  85C, T= 40
MANTLE WAVES:   15S,  15C, T=125
SURFACE WAVES:  50S, 104C, T= 50
TIMESTAMP:      Q-20071031072823
CENTROID LOCATION:
ORIGIN TIME:      03:04:59.7 0.2
LAT:37.44N 0.02;LON:121.78W 0.02
DEP: 15.2  1.0;TRIANG HDUR:  1.5
MOMENT TENSOR: SCALE 10**24 D-CM
RR=-0.330 0.054; TT=-2.270 0.053
PP= 2.600 0.059; RT= 0.553 0.183
RP= 0.496 0.160; TP= 0.947 0.050
PRINCIPAL AXES:
1.(T) VAL=  2.887;PLG=11;AZM=282
2.(N)      -0.344;    74;     52
3.(P)      -2.543;    12;    189
BEST DBLE.COUPLE:M0= 2.71*10**24
NP1: STRIKE=326;DIP=74;SLIP=-179
NP2: STRIKE=235;DIP=89;SLIP= -16

            -----------           
        -------------------       
      #####------------------     
    #########------------------   
   ############--------------###  
  ###############----------###### 
    ##############------######### 
  T ################-#############
    ##############---#############
 ###############------############
 ############----------###########
  #########-------------######### 
  ######-----------------######## 
   ##---------------------######  
    ----------------------#####   
      --------   ----------##     
        ------ P ----------       
            --   ------           

        
UCB Seismological Laboratory

Inversion method:   complete waveform
Stations used:      CMB MCCM ORV PKD RO4C SO5C
 
 Berkeley Moment Tensor Solution
 
 Best Fitting Double-Couple:
    Mo = 2.05E+24 Dyne-cm
    Mw = 5.48
    Z  = 14
    Plane   Strike   Rake   Dip
     NP1      146    -178    89
     NP2       56      -1    88
 
 Principal Axes:
    Axis    Value   Plunge   Azimuth
      T     2.049       1      281
      N     0.000      88      173
      P    -2.049       2       11
 
 Event Date/Time: October 31, 2007, 03:04:54.82 UTC
 Event ID:        nc40204628
 Moment Tensor: Scale = 10**24 Dyne-cm
    Component   Value
       Mxx     -1.898
       Mxy     -0.766
       Mxz     -0.070
       Myy      1.900
       Myz     -0.039
       Mzz     -0.002
 
                                               
                                               
                    ------ P                   
              ------------   ----              
           #------------------------           
         ####-------------------------         
       ########-------------------------       
      ##########------------------------#      
     ############--------------------#####     
    ##############-----------------########    
     ###############------------###########    
   T ################---------##############   
     #################-----#################   
   ####################-####################   
   ###################--####################   
   ################-------##################   
    ############-----------################    
    #########---------------###############    
     #####--------------------############     
      #------------------------##########      
       -------------------------########       
         ------------------------#####         
           ------------------------#           
              -------------------              
                    -------                    
                                               
     Lower Hemisphere Equiangle Projection
 

        

Waveform Inversion

The focal mechanism was determined using broadband seismic waveforms. The location of the event and the and stations used for the waveform inversion are shown in the next figure.
Location of broadband stations used for waveform inversion

The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.

The observed and predicted traces are filtered using the following gsac commands:

hp c 0.01 n 3
lp c 0.05 n 3
br c 0.12 0.25 n 4 p 2
The results of this grid search from 0.5 to 19 km depth are as follow:

           DEPTH  STK   DIP  RAKE   MW    FIT
WVFGRD96    0.5    55    80    25   5.25 0.3269
WVFGRD96    1.0    55    80    15   5.26 0.3448
WVFGRD96    2.0   235    70    15   5.33 0.4115
WVFGRD96    3.0   235    60    10   5.38 0.4403
WVFGRD96    4.0   235    90   -25   5.38 0.4609
WVFGRD96    5.0   235    85   -20   5.39 0.4760
WVFGRD96    6.0   235    85   -20   5.41 0.4873
WVFGRD96    7.0   235    80   -20   5.42 0.4974
WVFGRD96    8.0   230    75   -25   5.45 0.5044
WVFGRD96    9.0   235    80   -20   5.45 0.5115
WVFGRD96   10.0   235    80   -20   5.46 0.5152
WVFGRD96   11.0   235    80   -20   5.47 0.5162
WVFGRD96   12.0   235    85   -15   5.48 0.5162
WVFGRD96   13.0   235    85   -15   5.49 0.5147
WVFGRD96   14.0   235    80   -15   5.50 0.5117
WVFGRD96   15.0   235    80   -15   5.50 0.5079
WVFGRD96   16.0   235    80   -15   5.51 0.5038
WVFGRD96   17.0   235    80   -15   5.52 0.4986
WVFGRD96   18.0   235    80   -15   5.53 0.4931
WVFGRD96   19.0   235    80   -15   5.53 0.4866
WVFGRD96   20.0   235    80   -15   5.54 0.4799
WVFGRD96   21.0   235    80   -15   5.55 0.4724
WVFGRD96   22.0   235    80   -15   5.56 0.4642
WVFGRD96   23.0   235    80   -15   5.56 0.4559
WVFGRD96   24.0   235    80   -15   5.57 0.4473
WVFGRD96   25.0   235    80   -15   5.57 0.4388
WVFGRD96   26.0   235    80   -15   5.58 0.4305
WVFGRD96   27.0   235    80   -15   5.59 0.4222
WVFGRD96   28.0   235    80   -15   5.59 0.4138
WVFGRD96   29.0   235    80   -15   5.60 0.4057

The best solution is

WVFGRD96   12.0   235    85   -15   5.48 0.5162

The mechanism correspond to the best fit is
Figure 1. Waveform inversion focal mechanism

The best fit as a function of depth is given in the following figure:

Figure 2. Depth sensitivity for waveform mechanism

The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted. Each observed-predicted componnet is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. The number in black at the rightr of each predicted traces it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed and because the velocity model used in the predictions may not be perfect. A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow. The bandpass filter used in the processing and for the display was

hp c 0.01 n 3
lp c 0.05 n 3
br c 0.12 0.25 n 4 p 2
Figure 3. Waveform comparison for depth of 8 km
Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure.

Surface-Wave Focal Mechanism

The following figure shows the stations used in the grid search for the best focal mechanism to fit the surface-wave spectral amplitudes of the Love and Rayleigh waves.
Location of broadband stations used to obtain focal mechanism from surface-wave spectral amplitudes

The surface-wave determined focal mechanism is shown here.


  NODAL PLANES 

  
  STK=      59.99
  DIP=      80.00
 RAKE=      29.99
  
             OR
  
  STK=     324.26
  DIP=      60.51
 RAKE=     168.49
 
 
DEPTH = 12.0 km
 
Mw = 5.55
Best Fit 0.8661 - P-T axis plot gives solutions with FIT greater than FIT90

First motion data

The P-wave first motion data for focal mechanism studies are as follow:

Sta Az(deg)    Dist(km)   First motion
WENL        3   21 -12345
JRSC      266   42 -12345
BDM       352   59 -12345
PACP      137   63 -12345
SAO       159   79 -12345
FARB      286  113 -12345
CVS       329  118 -12345
R04C       38  118 -12345
MCCM      309  126 -12345
S05C       94  128 -12345
Q03C      351  135 -12345
CMB        61  139 -12345
U04C      143  148 -12345
V03C      163  163 -12345
MNRC      340  171 -12345
LAVA       31  173 -12345
T06C      104  189 -12345
U05C      129  191 -12345
PKD       146  198 -12345
HOPS      327  208 -12345
KCC        92  217 -12345
ORV         6  237 -12345
R06C       59  237 -12345
V05C      136  241 -12345
PHL       154  250 -12345
RCT       118  258 -12345
GASB      342  260 -12345
MLAC       84  260 -12345
WCN        40  272 -12345
SMM       145  284 -12345
O05C       15  291 -12345
BEK        24  297 -12345
P06A       33  298 -12345
VES       125  298 -12345
Q07A       56  309 -12345
TIN        96  317 -12345
O04C       10  326 -12345
MPP       147  332 -12345
R08A       71  338 -12345
P07A       46  344 -12345
CWC       107  347 -12345
O06A       28  347 -12345
O01C      330  350 -12345
ISA       123  354 -12345
WDC       349  356 -12345
ARV       133  367 -12345
Q08A       64  372 -12345
SBC       150  380 -12345
GRA        96  394 -12345
O07A       39  394 -12345
N02C      341  399 -12345
S09A       84  403 -12345
N06A       24  405 -12345
TPH        78  407 -12345
P08A       51  408 -12345
MPM       110  411 -12345
R09A       76  423 -12345
JCC       333  424 -12345
LRL       119  426 -12345
SCZ2      152  427 -12345
M03C      356  428 -12345
Q09A       67  431 -12345
SLA       112  436 -12345
EDW2      129  442 -12345
LGU       146  442 -12345
N07B       32  444 -12345
O08A       44  446 -12345
FUR       102  450 -12345
M02C      348  450 -12345
S10A       82  460 -12345
VCS       134  464 -12345
P09A       58  468 -12345
DEC       138  470 -12345
DJJ       140  475 -12345
CHF       134  482 -12345
YBH       351  484 -12345
PASC      137  485 -12345
PASC      137  485 -12345
N08A       39  487 -12345
MWC       136  489 -12345
R10A       77  490 -12345
TPNV       95  493 -12345
Q10A       70  496 -12345
U10A      101  497 -12345

Surface-wave analysis

Surface wave analysis was performed using codes from Computer Programs in Seismology, specifically the multiple filter analysis program do_mft and the surface-wave radiation pattern search program srfgrd96.

Data preparation

Digital data were collected, instrument response removed and traces converted to Z, R an T components. Multiple filter analysis was applied to the Z and T traces to obtain the Rayleigh- and Love-wave spectral amplitudes, respectively. These were input to the search program which examined all depths between 1 and 25 km and all possible mechanisms.
Best mechanism fit as a function of depth. The preferred depth is given above. Lower hemisphere projection

Pressure-tension axis trends. Since the surface-wave spectra search does not distinguish between P and T axes and since there is a 180 ambiguity in strike, all possible P and T axes are plotted. First motion data and waveforms will be used to select the preferred mechanism. The purpose of this plot is to provide an idea of the possible range of solutions. The P and T-axes for all mechanisms with goodness of fit greater than 0.9 FITMAX (above) are plotted here.


Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the Love and Rayleigh wave radiation patterns. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. Because of the symmetry of the spectral amplitude rediation patterns, only strikes from 0-180 degrees are sampled.

Love-wave radiation patterns

Rayleigh-wave radiation patterns

Broadband station distribution

The distribution of broadband stations with azimuth and distance is

Sta Az(deg)    Dist(km)   
CCM	  309	  126
MCCM	  309	  126
CMB	   61	  139
U04C	  143	  148
V03C	  163	  163
MNRC	  340	  171
LAVA	   31	  173
PKD	  146	  198
HOPS	  327	  208
KCC	   92	  217
ORV	    6	  237
R06C	   58	  237
V05C	  136	  241
PHL	  154	  250
RCT	  118	  258
GASB	  342	  260
MLAC	   84	  260
WCN	   40	  272
SMM	  145	  284
O05C	   14	  291
P06A	   33	  298
VES	  126	  298
Q07A	   56	  309
TIN	   96	  317
O04C	   10	  326
MPP	  147	  332
R08A	   71	  338
P07A	   46	  344
CWC	  107	  347
O06A	   28	  347
O01C	  330	  350
ISA	  123	  354
WDC	  349	  356
Q08A	   64	  372
SBC	  150	  380
GRA	   96	  394
O07A	   39	  394
N02C	  341	  399
S09A	   84	  403
N06A	   24	  405
TPH	   78	  407
P08A	   51	  408
MPM	  110	  411
R09A	   76	  423
LRL	  119	  426
SCZ2	  152	  427
M03C	  356	  428
Q09A	   67	  431
SLA	  112	  436
EDW2	  129	  442
LGU	  146	  442
N07B	   32	  444
O08A	   44	  446
FUR	  102	  450
M02C	  348	  450
S10A	   82	  460
VCS	  134	  464
P09A	   58	  468
DEC	  138	  470
DJJ	  140	  475
CHF	  134	  482
YBH	  351	  484
N08A	   39	  487
MWC	  136	  489
R10A	   77	  490
TPNV	   95	  493
Q10A	   70	  496
U10A	  101	  497
GSC	  116	  504
SNCC	  156	  507
RPV	  142	  510
VTV	  127	  511
MOD	   14	  512
BFS	  132	  513
RRX	  122	  515
BMN	   48	  516
FMP	  142	  519
SHO	  107	  520
P10A	   61	  523
N09A	   43	  528
M01C	  338	  530
M08A	   32	  533
S11A	   86	  533
L02A	  344	  548
L07A	   22	  550
R11A	   78	  553
O10A	   54	  557
Q11A	   72	  559
BBR	  127	  561
SVD	  130	  561
HEC	  119	  568
SDD	  138	  569
TUQ	  111	  569
SCI2	  148	  574
P11A	   64	  575
M09A	   39	  579
U11A	   99	  580
T11A	   90	  581
N10A	   50	  583
HUMO	  350	  584
K05A	    7	  593
MUR	  134	  594
V11A	  105	  594
DGR	  133	  602
L08A	   28	  604
SMER	  135	  607
K02A	  347	  610
K06A	   12	  610
O11A	   59	  610
S12A	   86	  612
RDM	  132	  614
KNW	  130	  616
WVOR	   25	  617
L09A	   33	  619
K07A	   19	  622
GMR	  116	  623
CRY	  132	  626
WMC	  131	  630
T12A	   95	  632
Q12A	   72	  633
PLM	  134	  635
SND	  131	  635
BZN	  132	  637
R12A	   79	  638
M10A	   43	  639
K01A	  340	  640
FRD	  131	  641
PFO	  130	  641
N11A	   52	  643
DBO	  349	  644
BEL	  124	  646
J05A	    4	  652
K08A	   24	  652
DAN	  116	  654
U12A	   98	  654
LVA2	  132	  655
SOL	  140	  655
HWB	  137	  656
109C	  138	  659
J06A	   12	  661
W12A	  109	  663
J03A	  352	  668
BVDA2	  131	  669
ELK	   55	  674
J02A	  348	  677
K09A	   29	  679
M11A	   47	  680
O12A	   60	  686
L10A	   40	  687
J07A	   17	  692
R13A	   81	  692
N12A	   55	  695
Q13A	   74	  699
S13A	   86	  699
T13A	   91	  699
IRM	  119	  700
MONP2	  134	  700
NEE2	  112	  708
BC3	  124	  709
I04A	  356	  709
P13A	   69	  713
PIN	    6	  713
J08A	   22	  715
K10A	   34	  726
TAKO	  345	  728
I06A	   10	  735
L11A	   42	  736
WIFE	  360	  736
M12A	   51	  737
SWS	  131	  737
I03A	  350	  738
DVT	  134	  740
J09A	   26	  740
O13A	   64	  740
EUO	  352	  741
I05A	    3	  749
I02A	  347	  750
W13A	  108	  754
N13A	   58	  756
S14A	   85	  760
I07A	   14	  763
Q14A	   74	  763
K11A	   38	  768
I08A	   20	  769
PDM	  114	  771
T14A	   90	  771
U14A	   96	  773
Y12C	  120	  773
R14A	   80	  776
L12A	   46	  780
J10A	   31	  789
P14A	   70	  796
GLA	  126	  797
V14A	  102	  801
I09A	   24	  802
H05A	    3	  803
COR	  351	  805
H04A	  358	  806
H03A	  352	  815
H07A	   12	  817
W14A	  105	  818
TOLO	  348	  819
H06A	    8	  820
K12A	   43	  823
Y13A	  117	  823
H02A	  348	  826
H08A	   17	  829
S15A	   85	  831
N14A	   60	  833
J11A	   35	  834
T15A	   90	  834
DUG	   66	  836
Q15A	   75	  840
R15A	   81	  840
L13A	   50	  846
I10A	   28	  849
112A	  128	  851
U15A	   95	  851
M14A	   55	  854
J12A	   39	  859
X14A	  110	  865
G04A	  356	  866
O15A	   66	  867
G05A	    2	  868
I11A	   32	  871
G06A	    6	  872
H09A	   22	  874
K13A	   46	  875
HOOD	    1	  876
V15A	   99	  876
Y14A	  113	  882
G03A	  352	  885
N15A	   62	  886
G07A	   11	  888
W15A	  104	  889
L14A	   52	  892
113A	  123	  894
S16A	   85	  899
H10A	   26	  900
I12A	   36	  902
G08A	   14	  904
BMO	   23	  905
R16A	   81	  910
T16A	   90	  912
P16A	   72	  914
M15A	   58	  918
X15A	  108	  919
Z14A	  117	  919
HLID	   40	  923
J13A	   42	  924
K14A	   50	  927
F06A	    5	  930
G09A	   20	  933
Y15A	  112	  937
F05A	    2	  939
H11A	   29	  941
O16A	   68	  943
Q16A	   77	  943
F04A	  357	  946
L15A	   55	  951
F07A	    9	  953
W16A	  103	  955
WUAZ	  100	  955
F03A	  352	  956
G10A	   22	  956
J14A	   44	  958
U16A	   95	  960
F08A	   14	  962
I13A	   40	  967
S17A	   85	  969
N16A	   64	  971
F09A	   18	  974
M16A	   61	  974
T17A	   90	  974
R17A	   80	  978
K15A	   51	  980
H12A	   34	  981
Z15A	  115	  986
P17A	   73	  988
X16A	  107	  990
HWUT	   59	  992
U17A	   92	  992
G11A	   26	  997
SRU	   76	 1001
O17A	   69	 1005
I14A	   42	 1007
HAWA	   10	 1013
E05A	    0	 1014
E06A	    3	 1014
115A	  118	 1015
214A	  124	 1020
E04A	  356	 1021
F10A	   20	 1021
L16A	   57	 1021
N17A	   64	 1021
E07A	    8	 1026
W17A	  101	 1027
E08A	   12	 1031
J15A	   47	 1032
P18A	   73	 1033
Q18A	   76	 1034
S18A	   85	 1040
Z16A	  113	 1043
X17A	  106	 1047
F11A	   25	 1049
R18A	   81	 1049
K16A	   52	 1054
T18A	   88	 1055
G13A	   34	 1059
116A	  118	 1065
H14A	   39	 1065
U18A	   92	 1066
O18A	   69	 1068
I15A	   44	 1070
F12A	   28	 1072
Y17A	  110	 1073
V18A	   97	 1076
E10A	   20	 1077
J16A	   50	 1078
D04A	  356	 1079
AHID	   54	 1084
D05A	  359	 1084
D06A	    4	 1087
D03A	  352	 1088
E11A	   23	 1093
D07A	    7	 1095
D08A	   12	 1095
R19A	   81	 1104
H15A	   41	 1106
D09A	   14	 1107
Q19A	   77	 1108
W18A	  100	 1110
G14A	   36	 1111
X18A	  103	 1113
F13A	   31	 1115
N18A	   66	 1115
S19A	   84	 1116
216A	  120	 1119
E12A	   25	 1122
Z17A	  111	 1123
I16A	   47	 1125
D10A	   18	 1131
T19A	   90	 1134
Y18A	  107	 1137
C05A	    0	 1140
P19A	   74	 1140
117A	  115	 1141
W19A	   99	 1141
O19A	   70	 1142
J17A	   52	 1145
C04A	  356	 1147
N19A	   67	 1153
TUC	  116	 1153
V19A	   96	 1154
G15A	   39	 1157
D11A	   21	 1158
F14A	   34	 1163
C06A	    3	 1168
Z18A	  111	 1170
C08A	   10	 1172
X19A	  103	 1173
M19A	   64	 1174
MVCO	   87	 1176
E13A	   30	 1181
L19A	   60	 1182
217A	  119	 1183
C09A	   13	 1187
I17A	   49	 1188
B04A	  354	 1189
C03A	  350	 1190
D12A	   24	 1192
OPC	  354	 1193
BW06	   56	 1196
H16A	   44	 1196
118A	  113	 1200
G16A	   41	 1201
B05A	  359	 1204
C10A	   16	 1210
E14A	   32	 1210
F15A	   37	 1211
H17A	   47	 1218
Z19A	  108	 1224
I18A	   52	 1227
MSO	   29	 1227
VGZ	  355	 1227
B08A	    8	 1230
D13A	   27	 1230
218A	  116	 1232
B06A	    1	 1232
B07A	    6	 1233
BOZ	   40	 1243
119A	  111	 1248
C12B	   22	 1252
F16A	   39	 1253
PGC	  354	 1254
A04A	  357	 1256
B09A	   12	 1256
PFB	  351	 1257
NEW	   16	 1261
B10A	   16	 1263
SNB	  355	 1266
318A	  118	 1269
D14A	   30	 1269
G17A	   43	 1270
C13A	   25	 1281
A05A	  359	 1285
YOUB	  352	 1290
219A	  114	 1293
A06A	    1	 1296
A07A	    4	 1296
A08A	    8	 1296
B11A	   18	 1299
MGB	  350	 1307
A09A	   10	 1308
D15A	   32	 1310
E16A	   36	 1310
OZB	  348	 1316
F17A	   41	 1318
HNB	  357	 1318
NLLB	  353	 1323
B12A	   20	 1325
A10A	   14	 1328
319A	  117	 1329
HOPB	    1	 1329
PNT	    7	 1332
G18A	   46	 1343
E17A	   38	 1348
RLMT	   47	 1349
A11	   17	 1353
A11A	   17	 1353
B13A	   24	 1353
D16A	   35	 1357
SHB	  354	 1362
A12A	   19	 1370
BTB	  348	 1371
C15A	   30	 1371
F18A	   43	 1373
Y22D	  101	 1392
B14A	   27	 1397
ANMO	   97	 1403
E18A	   40	 1409
D17A	   37	 1412
C16A	   32	 1413
B15A	   29	 1422
CBB	  350	 1429
ISCO	   74	 1429
SDCO	   84	 1436
WALA	   24	 1439
C17A	   35	 1447
EDB	  344	 1447
A14A	   25	 1449
D18A	   38	 1463
LLLB	  360	 1464
B16A	   31	 1468
A15A	   27	 1476
A16	   30	 1521
A16A	   30	 1521
EGMT	   36	 1530
PHC	  345	 1542
SLEB	   10	 1553
FLLB	  357	 1594
TALB	  354	 1632
LAO	   46	 1642
RSSD	   58	 1666
THMB	  354	 1690
ALRB	  352	 1696
CLSB	  358	 1705
BBB	  345	 1713
UBRB	  355	 1728
OGNE	   71	 1745
SULB	  354	 1773
AMTX	   93	 1826
EDM	   18	 1872
DGMT	   44	 1879
MOBC	  339	 1917
CBKS	   79	 1933
DIB	  338	 1939
VIB	  338	 1946
RUBB	  344	 1987
BMBC	  359	 2070
JCT	  104	 2166
KSU1	   77	 2203
ECSD	   64	 2232
FNBB	  358	 2388
DLBC	  348	 2412
AGMN	   52	 2420
KVTX	  109	 2488
SCIA	   70	 2488
ULM	   47	 2502
HKT	  102	 2534
MIAR	   89	 2553
NATX	   96	 2555
EPLO	   50	 2620
UALR	   87	 2655
PLBC	  342	 2663
EYMN	   55	 2719
JFWS	   67	 2736
ATKO	   53	 2737
FVM	   79	 2751
SLM	   78	 2758
HDIL	   73	 2819
PVMO	   82	 2846
COWI	   60	 2855
MPH	   85	 2858
SIUC	   79	 2861
LDIO	   53	 2889
VBMS	   92	 2903
PKLO	   48	 2915
UTMT	   82	 2921
OXF	   86	 2922
MUMO	   45	 2957
USIN	   78	 2991
ROMN	    4	 3001
WVT	   82	 3017
CTLN	    5	 3028
BLO	   75	 3070
FCC	   31	 3098
NSKO	   47	 3098
WCI	   77	 3105
COWN	    9	 3174
DAWY	  344	 3188
GLMI	   63	 3196
JERN	    9	 3250
BRAL	   92	 3258
ARV	  133	 3264
ARVN	   27	 3264
AAM	   68	 3278
ACSO	   72	 3356
KAPO	   54	 3400
BRCO	   64	 3448
ELFO	   66	 3463
OTRO	   53	 3474
TRO	  130	 3474
GOGA	   86	 3483
COLA	  339	 3500
INK	  352	 3512
JOSN	   26	 3514
SEDN	   26	 3533
CLWO	   64	 3538
KLBO	   62	 3543
ACTO	   66	 3562
ALLY	   69	 3574
ERPA	   68	 3581
KILO	   56	 3591
MALO	   54	 3604
BUKO	   62	 3607
ADO	  128	 3629
SADO	   63	 3629
BLA	   78	 3635
MEDO	   66	 3695
BULN	   21	 3705
ALGO	   61	 3711
BANO	   63	 3724
VLDQ	   57	 3735
DELO	   64	 3751
SSPA	   71	 3777
SNQN	   42	 3781
STLN	   20	 3783
NHSC	   85	 3784
WAGN	   23	 3787
PECO	   65	 3806
KGNO	   64	 3843
MPPO	   63	 3856
CBN	   75	 3872
DWPF	   93	 3886
SDMD	   73	 3889
OTT	   62	 3895
INUQ	   39	 3905
BINY	   68	 3908
CNNC	   80	 3911
MVL	   72	 3918
QILN	   23	 3948
ALFO	   62	 3958
PTN	   63	 3960
AKVQ	   35	 3987
LONY	   63	 3991
MRHQ	   61	 4008
NCB	   64	 4026
BRNJ	   70	 4053
MNT	   62	 4057
IVKQ	   33	 4066
FRNY	   63	 4067
ACCN	   65	 4079
CPNY	   70	 4101
PAL	   69	 4101
FOR	   69	 4106
CUNY	   70	 4114
SRLN	   22	 4178
LBNH	   64	 4206
LAIN	   21	 4208
HRV	   66	 4264
ILON	   21	 4280
LMQ	   58	 4292
A61	   58	 4309
GIFN	   21	 4326
RES	   11	 4382
PKME	   62	 4397
ICQ	   55	 4502
FRB	   33	 4561
GGN	   61	 4592
LMN	   60	 4734
GBN	   60	 4995
DRLN	   54	 5208
SJNN	   55	 5598

Waveform comparison for this mechanism

Since the analysis of the surface-wave radiation patterns uses only spectral amplitudes and because the surfave-wave radiation patterns have a 180 degree symmetry, each surface-wave solution consists of four possible focal mechanisms corresponding to the interchange of the P- and T-axes and a roation of the mechanism by 180 degrees. To select one mechanism, P-wave first motion can be used. This was not possible in this case because all the P-wave first motions were emergent ( a feature of the P-wave wave takeoff angle, the station location and the mechanism). The other way to select among the mechanisms is to compute forward synthetics and compare the observed and predicted waveforms.

The fits to the waveforms with the given mechanism are show below:

This figure shows the fit to the three components of motion (Z - vertical, R-radial and T - transverse). For each station and component, the observed traces is shown in red and the model predicted trace in blue. The traces represent filtered ground velocity in units of meters/sec (the peak value is printed adjacent to each trace; each pair of traces to plotted to the same scale to emphasize the difference in levels). Both synthetic and observed traces have been filtered using the SAC commands:

hp c 0.01 n 3
lp c 0.05 n 3
br c 0.12 0.25 n 4 p 2

Discussion

The Future

Should the national backbone of the USGS Advanced National Seismic System (ANSS) be implemented with an interstation separation of 300 km, it is very likely that an earthquake such as this would have been recorded at distances on the order of 100-200 km. This means that the closest station would have information on source depth and mechanism that was lacking here.

Acknowledgements

Dr. Harley Benz, USGS, provided the USGS USNSN digital data. The digital data used in this study were provided by Natural Resources Canada through their AUTODRM site http://www.seismo.nrcan.gc.ca/nwfa/autodrm/autodrm_req_e.php, and IRIS using their BUD interface

Appendix A


Spectra fit plots to each station

Velocity Model

The WUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:

MODEL.01
Model after     8 iterations
ISOTROPIC
KGS
FLAT EARTH
1-D
CONSTANT VELOCITY
LINE08
LINE09
LINE10
LINE11
      H(KM)   VP(KM/S)   VS(KM/S) RHO(GM/CC)         QP         QS       ETAP       ETAS      FREFP      FREFS
     1.9000     3.4065     2.0089     2.2150  0.302E-02  0.679E-02   0.00       0.00       1.00       1.00    
     6.1000     5.5445     3.2953     2.6089  0.349E-02  0.784E-02   0.00       0.00       1.00       1.00    
    13.0000     6.2708     3.7396     2.7812  0.212E-02  0.476E-02   0.00       0.00       1.00       1.00    
    19.0000     6.4075     3.7680     2.8223  0.111E-02  0.249E-02   0.00       0.00       1.00       1.00    
     0.0000     7.9000     4.6200     3.2760  0.164E-10  0.370E-10   0.00       0.00       1.00       1.00    

Quality Control

Here we tabulate the reasons for not using certain digital data sets

The following stations did not have a valid response files:

DATE=Thu Nov 1 21:59:42 CDT 2007

Last Changed 2007/10/31