Location

2007/06/25 02:32:26 41.125 -124.814 10 5.1 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
 2007/06/25 02:32:26 41.125 -124.814 10 5.1 California
 
 Best Fitting Double Couple
    Mo = 2.63e+23 dyne-cm
    Mw = 4.88 
    Z  = 28 km
     Plane   Strike  Dip  Rake
      NP1      305    90   -155
      NP2      215    65     0
 Principal Axes:
   Axis    Value   Plunge  Azimuth
     T   2.63e+23     17      77
     N   0.00e+00     65     305
     P  -2.63e+23     17     173



 Moment Tensor: (dyne-cm)
    Component  Value
       Mxx    -2.24e+23
       Mxy     8.15e+22
       Mxz     9.11e+22
       Myy     2.24e+23
       Myz     6.38e+22
       Mzz     0.00e+00
                                                     
                                                     
                                                     
                                                     
                     --------------                  
                 ----------------------              
              ----------------------######           
             --------------------##########          
           -------------------###############        
          ###---------------##################       
         #######-----------####################      
        ###########------##################   ##     
        #############--#################### T ##     
       ###############--###################   ###    
       ##############------######################    
       #############---------####################    
       ############-------------#################    
        ##########-----------------#############     
        ##########-------------------###########     
         ########-----------------------#######      
          ######---------------------------###       
           #####-----------------------------        
             ###---------------------------          
              ##-------------   ----------           
                 ------------ P -------              
                     --------   ---                  
                                                     
                                                     
                                                     

 Harvard Convention
 Moment Tensor:
      R          T          F
  0.00e+00   9.11e+22  -6.38e+22 
  9.11e+22  -2.24e+23  -8.15e+22 
 -6.38e+22  -8.15e+22   2.24e+23 


Details of the solution is found at

http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20070625023226/index.html
        
This is a preliminary UCB moment tensor solution for the event located
57 km ( 35 miles) W   (277 degrees) of Trinidad, CA; 41.1247N
124.8145W; Z=10.1km;  ML=5.1; (USGS/UCB Joint Notification System) on
June 25, 2007 at 02:32:25    UTC. Other information about this event
can be viewed at:
http://earthquake.usgs.gov/recenteqsus/Quakes/nc51183469.php

Reviewed by:
ahyi kim
UCB Seismological Laboratory

Inversion method:   complete waveform
Stations used:      HUMO, JCC, ORV, YBH, and HOPS
 
 Berkeley Moment Tensor Solution
 
 Best Fitting Double-Couple:
    Mo = 3.17E+23 Dyne-cm
    Mw = 4.94
    Z  = 24
    Plane   Strike   Rake   Dip
     NP1      306    -170    87
     NP2      215      -3    80
 
 Principal Axes:
    Axis    Value   Plunge   Azimuth
      T     3.170       5       80
      N     0.000      80      323
      P    -3.170       9      171
 
 Event Date/Time: June 25, 2007 at 02:32:25    UTC
 Event ID:        nc51183469
 Moment Tensor: Scale = 10**23 Dyne-cm
    Component   Value
       Mxx     -2.927
       Mxy      0.991
       Mxz      0.539
       Myy      2.985
       Myz      0.190
       Mzz     -0.058
 
                                               
                                               
                    -------                    
              -------------------              
           ------------------------#           
         ------------------------#####         
       ------------------------#########       
      ###--------------------############      
     ######-----------------##############     
    ##########------------#################    
    #############--------################      
   #################---################## T    
   ######################################      
   ##################----###################   
   ################--------#################   
   ###############------------##############   
    #############---------------###########    
    ############------------------#########    
     ##########----------------------#####     
      ########-------------------------##      
       ######---------------------------       
         ###--------------------------         
           #-------------   --------           
              ----------- P -----              
                    -----                      
                                               
     Lower Hemisphere Equiangle Projection

	

Preferred Solution

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

      STK = 215
      DIP = 65
     RAKE = 0
       MW = 4.88
       HS = 28

The waveform inversion is preferred. There is little depth control.

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 0.02 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    45    90   -10   4.58 0.4189
WVFGRD96    1.0    40    90   -15   4.61 0.4286
WVFGRD96    2.0    40    90   -10   4.63 0.4561
WVFGRD96    3.0    40    90    20   4.67 0.4787
WVFGRD96    4.0    35    85   -10   4.69 0.4940
WVFGRD96    5.0    35    85   -30   4.74 0.5161
WVFGRD96    6.0   215    95    20   4.74 0.5312
WVFGRD96    7.0   215    85     0   4.74 0.5484
WVFGRD96    8.0   215    75   -10   4.76 0.5614
WVFGRD96    9.0   215    75   -10   4.77 0.5660
WVFGRD96   10.0   215    70     0   4.80 0.5778
WVFGRD96   11.0   215    80     0   4.80 0.5778
WVFGRD96   12.0    35    95    -5   4.81 0.5714
WVFGRD96   13.0   215    80     0   4.81 0.5750
WVFGRD96   14.0   210    70     0   4.86 0.5714
WVFGRD96   15.0   215    75    10   4.84 0.5758
WVFGRD96   16.0   215    75    15   4.85 0.5667
WVFGRD96   17.0   215    75     5   4.84 0.5625
WVFGRD96   18.0   215    70     0   4.84 0.5625
WVFGRD96   19.0   220    75    15   4.82 0.5556
WVFGRD96   20.0   215    80    20   4.86 0.5556
WVFGRD96   21.0   215    65     5   4.86 0.5556
WVFGRD96   22.0   220    70    10   4.83 0.5455
WVFGRD96   23.0   215    65    -5   4.85 0.5517
WVFGRD96   24.0   215    60     0   4.86 0.5556
WVFGRD96   25.0   215    60     5   4.87 0.5600
WVFGRD96   26.0   220    70     0   4.84 0.5625
WVFGRD96   27.0   215    65     0   4.88 0.5600
WVFGRD96   28.0   215    65     0   4.88 0.5833
WVFGRD96   29.0   220    65     5   4.86 0.5714

The best solution is

WVFGRD96   28.0   215    65     0   4.88 0.5833

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 0.02 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=     130.00
  DIP=      90.00
 RAKE=    -155.00
  
             OR
  
  STK=      40.00
  DIP=      65.00
 RAKE=       0.00
 
 
DEPTH = 10.0 km
 
Mw = 4.85
Best Fit 0.8960 - 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
YBH        68  188 -12345
HUMO       43  226 -12345
HOPS      147  279 -12345
MCCM      153  370 -12345
MOD        76  386 -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)   
N02C	  104	  131
M02C	   79	  167
YBH	   68	  188
O02C	  121	  201
P01C	  145	  223
HUMO	   42	  226
M03C	   85	  226
M04C	   73	  259
O03C	  117	  267
L04A	   63	  270
HATC	   96	  284
J03A	   31	  293
K04A	   56	  305
M05C	   84	  309
J04A	   43	  324
O04C	  105	  327
SUTB	  128	  333
L05A	   72	  347
ELFS	   98	  349
O05C	  110	  354
I04A	   33	  356
M06C	   87	  364
Q03C	  138	  366
K05A	   60	  371
J05A	   50	  381
MOD	   76	  386
Q04C	  130	  388
P05C	  118	  411
H03A	   17	  414
K06A	   62	  421
N06A	   94	  421
O06A	  103	  435
LAVA	  126	  436
I05A	   40	  445
P06A	  110	  447
H04A	   28	  450
J06A	   57	  452
R04C	  132	  460
L07A	   76	  467
M07A	   85	  474
R05C	  122	  486
H05A	   36	  489
G04A	   22	  491
I06A	   49	  491
K07A	   68	  493
N07B	   92	  493
S04C	  142	  502
CMB	  131	  512
O07A	  100	  513
J07A	   59	  518
WVOR	   72	  534
M08A	   84	  540
H06A	   41	  542
R06C	  120	  542
I07A	   51	  545
L08A	   76	  552
K08A	   69	  554
N08A	   92	  564
Q07A	  113	  567
F04A	   19	  568
G06A	   35	  569
O08A	   97	  570
S05C	  136	  571
J08A	   62	  579
T05C	  141	  591
F05A	   26	  594
HAST	  151	  597
I08A	   57	  599
R07C	  122	  599
L09A	   78	  604
F06A	   31	  610
E03A	    9	  611
K09A	   71	  613
N09A	   90	  614
M09A	   84	  618
G07A	   40	  621
H08A	   51	  628
E04A	   15	  630
J09A	   65	  633
U04C	  145	  634
T06C	  134	  636
Q08A	  111	  639
E05A	   21	  652
R08A	  116	  652
O09A	   97	  653
F07A	   35	  661
I09A	   59	  661
G08A	   44	  663
U05C	  141	  670
P09A	  102	  675
E06A	   26	  676
K10A	   72	  683
D04A	   13	  684
M10A	   84	  694
Q09A	  109	  700
S08C	  123	  700
N10A	   91	  701
L10A	   79	  703
H09A	   54	  704
HELL	  133	  704
O10A	   95	  708
D05A	   18	  710
J10A	   66	  711
F08A	   41	  712
E07A	   32	  723
HAWA	   34	  723
P10A	  100	  728
G09A	   49	  734
I10A	   61	  735
R09A	  113	  737
BMO	   53	  739
D06A	   24	  745
C04A	   11	  747
K11A	   73	  750
E08A	   36	  754
S09A	  118	  754
F09A	   45	  756
M11A	   84	  756
Q10A	  107	  762
H10A	   57	  763
L11A	   78	  763
N11A	   90	  765
C05A	   18	  771
D07A	   28	  777
G10A	   51	  777
O11A	   95	  782
J11A	   68	  783
P11A	  100	  789
I11A	   64	  790
S10A	  114	  791
R10A	  111	  795
E09A	   40	  803
ELK	   90	  807
D08A	   34	  810
F10A	   46	  815
C06A	   21	  817
H11A	   58	  821
ISA	  136	  821
B05A	   14	  822
C07A	   26	  822
Q11A	  105	  822
N12A	   89	  823
L12A	   79	  824
M12A	   84	  830
J12A	   70	  836
K12A	   75	  839
D09A	   36	  840
G11A	   53	  840
R11A	  108	  848
O12A	   93	  856
E10A	   44	  859
A04A	   10	  860
P12A	   99	  861
B06A	   17	  863
C08A	   30	  870
S11A	  113	  871
TPNV	  119	  874
F11A	   50	  877
Q12A	  102	  882
M13A	   85	  892
D10A	   40	  893
B07A	   23	  895
H12A	   62	  898
HLID	   69	  898
A05A	   13	  901
U10A	  123	  903
E11A	   47	  904
C09A	   33	  905
K13A	   76	  906
L13A	   80	  912
B08A	   26	  913
J13A	   70	  913
O13A	   93	  923
A06A	   15	  924
F12A	   53	  928
R12A	  106	  928
I13A	   67	  931
T11A	  114	  934
P13A	   98	  936
S12A	  111	  943
D11A	   43	  945
A07A	   20	  947
Q13A	  101	  951
C10A	   36	  953
GSC	  130	  953
M14A	   84	  960
G13A	   59	  966
B09A	   31	  967
U11A	  120	  971
A08A	   25	  973
N14A	   88	  978
K14A	   77	  979
F13A	   55	  993
B10A	   34	  998
NEW	   35	  999
A09A	   27	 1000
T12A	  116	 1002
D12A	   46	 1003
V11A	  123	 1006
HVU	   82	 1008
DUG	   92	 1019
S13A	  109	 1022
G14A	   60	 1029
U12A	  117	 1033
N15A	   87	 1034
M15A	   84	 1036
E13A	   52	 1038
A10A	   31	 1042
T13A	  112	 1047
B11A	   36	 1051
V12A	  121	 1055
R14A	  103	 1058
D13A	   48	 1060
F14A	   57	 1061
S14A	  107	 1069
MSO	   50	 1077
U13A	  116	 1077
P15A	   95	 1078
E14A	   53	 1083
W12A	  123	 1083
Q15A	   98	 1086
C13A	   45	 1092
B12A	   39	 1093
A11A	   34	 1094
G15A	   62	 1097
HWUT	   83	 1109
T14A	  110	 1109
V13A	  118	 1110
D14A	   50	 1120
R15A	  103	 1122
F15A	   58	 1124
A12A	   37	 1127
P16A	   94	 1129
U14A	  114	 1137
S15A	  106	 1138
E15A	   55	 1141
109C	  141	 1142
B13A	   42	 1147
C14A	   46	 1147
AHID	   76	 1150
T15A	  109	 1167
W13A	  121	 1167
REDW	   73	 1177
D15A	   52	 1182
Q16A	   97	 1189
V14A	  117	 1189
A13A	   40	 1191
LOHW	   72	 1201
U15A	  112	 1205
X13A	  123	 1207
W14A	  119	 1218
Y12C	  129	 1223
LKWY	   67	 1237
T16A	  108	 1239
V15A	  114	 1249
GLA	  132	 1260
Y13A	  126	 1264
BW06	   77	 1276
W15A	  117	 1281
X14A	  121	 1282
U16A	  110	 1312
Y14A	  124	 1312
112A	  133	 1318
X15A	  120	 1328
RLMT	   66	 1338
W16A	  116	 1341
113A	  130	 1350
Y15A	  122	 1358
Z14A	  126	 1358
X16A	  118	 1391
U18A	  107	 1397
W17A	  114	 1405
EGMT	   52	 1417
Z15A	  124	 1418
Y16A	  120	 1425
V18A	  110	 1429
X17A	  117	 1444
115A	  126	 1457
Z16A	  122	 1466
214A	  130	 1477
W18A	  112	 1478
Y17A	  119	 1484
X18A	  114	 1496
V19A	  108	 1499
116A	  125	 1504
W19A	  111	 1505
Y18A	  117	 1538
Z17A	  120	 1538
X19A	  114	 1553
216A	  126	 1563
117A	  123	 1570
Z18A	  120	 1584
Y19A	  115	 1585
LAO	   61	 1611
118A	  121	 1620
217A	  125	 1625
Z19A	  117	 1627
ISCO	   89	 1632
119A	  119	 1660
218A	  123	 1663
318A	  124	 1707
219A	  121	 1717
Y22C	  111	 1759
319A	  123	 1761
WRAK	  345	 1786
DGMT	   56	 1816
AMTX	  101	 2139
CBKS	   89	 2150
ECSD	   73	 2328
AGMN	   61	 2412
JCT	  110	 2538
SCIA	   78	 2624
EYMN	   63	 2731
MIAR	   95	 2828
EGAK	  344	 2832
COWI	   67	 2907
UALR	   93	 2921
SLM	   84	 2951
FVM	   85	 2957
HDIL	   79	 2975
PVMO	   88	 3075
MPH	   91	 3108
OXF	   92	 3179
USIN	   84	 3188
VBMS	   97	 3197
BLO	   81	 3244
PLAL	   90	 3270
GLMI	   69	 3271
AAM	   74	 3394
ACSO	   78	 3504
BRAL	   96	 3550
ALLY	   74	 3694
ERPA	   73	 3694
GOGA	   90	 3729
MCWV	   77	 3779
BLA	   82	 3819
BINY	   72	 4012
NHSC	   88	 4020
CBN	   79	 4033
SDMD	   76	 4033
LONY	   67	 4058
CNNC	   84	 4113
FRNY	   67	 4129
ACCN	   69	 4161
PAL	   73	 4216
LBNH	   67	 4273
PKME	   65	 4447

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 0.02 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=Tue Jun 26 06:20:07 MDT 2007

Last Changed 2007/06/25