2007/06/25 02:32:26 41.125 -124.814 10 5.1 California
USGS Felt map for this earthquake
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 |
STK = 215 DIP = 65 RAKE = 0 MW = 4.88 HS = 28
The waveform inversion is preferred. There is little depth control.
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.
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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 2The 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
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The best fit as a function of depth is given in the following figure:
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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
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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. |
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.
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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
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 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.
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.
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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. |
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
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
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.
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
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
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