2007/03/02 04:40:00 37.93N 122.14W 5. 4.2 California
USGS Felt map for this earthquake
USGS Felt reports page for California
SLU  UC Berkeley 
SLU Moment Tensor Solution 2007/03/02 04:40:00 37.93N 122.14W 5. 4.2 California Best Fitting Double Couple Mo = 3.55e+22 dynecm Mw = 4.30 Z = 12 km Plane Strike Dip Rake NP1 348 80 170 NP2 80 80 10 Principal Axes: Axis Value Plunge Azimuth T 3.55e+22 14 304 N 0.00e+00 76 125 P 3.55e+22 0 34 Moment Tensor: (dynecm) Component Value Mxx 1.38e+22 Mxy 3.20e+22 Mxz 4.65e+21 Myy 1.17e+22 Myz 6.98e+21 Mzz 2.11e+21 ### ######## P ############  ############## # ############ ## T ############# ### ############## ##################### ###################### ######################### ############################## ##################################### ###################################### ################# ################ ############### ############## ############# ########### ########## ####### ### Harvard Convention Moment Tensor: R T F 2.11e+21 4.65e+21 6.98e+21 4.65e+21 1.38e+22 3.20e+22 6.98e+21 3.20e+22 1.17e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20070302044000/index.html 
This is a preliminary UCB moment tensor solution for the event located 2km NE from Lafayette, CA; 7.9010N 122.0983W; Z=16.6km; ML=4.4; (USGS/UCB Joint Notification System) on March 2, 2007 at 04:40:00 UTC. Other information about this event can be viewed at: http://earthquake.usgs.gov/recenteqsus/Quakes/nc40194055.php Reviewed by: kim UCB Seismological Laboratory Inversion method: complete waveform Stations used: CMB, CVS, MCCM, WENL, Q03C Berkeley Moment Tensor Solution Best Fitting DoubleCouple: Mo = 2.60E+22 Dynecm Mw = 4.21 Z = 11.0 Plane Strike Rake Dip NP1 353 177 88 NP2 263 2 87 Principal Axes: Axis Value Plunge Azimuth T 2.600 1 128 N 0.000 86 27 P 2.600 4 218 Event Date/Time: March 2, 2007 at 04:40:00 UTC Event ID: nc40194055 Moment Tensor: Scale = 10**22 Dynecm Component Value Mxx 0.628 Mxy 2.517 Mxz 0.106 Myy 0.637 Myz 0.124 Mzz 0.009 # ####### ########### ############# ############### ################ ################## ################### ################### #################### ############################### ################################### ######################## #################### ################## ################## ################# #############  ############# T  P ############ ########## ####### # Lower Hemisphere Equiangle Projection 
STK = 80 DIP = 80 RAKE = 10 MW = 4.30 HS = 12
The surfacewave agrees with the waveform inversion solution. The waveform inversion solution is used to define the event. It also agrees with the UCB moment tensor.
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.

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 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.2 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 0.5 175 60 45 3.73 0.1892 WVFGRD96 1.0 105 90 30 3.76 0.2057 WVFGRD96 2.0 250 85 5 3.88 0.3064 WVFGRD96 3.0 70 90 0 3.98 0.3836 WVFGRD96 4.0 75 85 10 4.05 0.4651 WVFGRD96 5.0 80 75 15 4.12 0.5372 WVFGRD96 6.0 80 80 20 4.17 0.5977 WVFGRD96 7.0 80 80 15 4.20 0.6436 WVFGRD96 8.0 80 80 15 4.24 0.6761 WVFGRD96 9.0 80 80 10 4.26 0.6958 WVFGRD96 10.0 80 80 0 4.27 0.7065 WVFGRD96 11.0 80 80 10 4.28 0.7137 WVFGRD96 12.0 80 80 10 4.30 0.7189 WVFGRD96 13.0 80 80 10 4.30 0.7181 WVFGRD96 14.0 80 85 10 4.32 0.7179 WVFGRD96 15.0 80 85 10 4.33 0.7178 WVFGRD96 16.0 80 85 10 4.34 0.7107 WVFGRD96 17.0 80 85 15 4.34 0.7108 WVFGRD96 18.0 80 85 15 4.35 0.7031 WVFGRD96 19.0 80 85 15 4.36 0.7032
The best solution is
WVFGRD96 12.0 80 80 10 4.30 0.7189
The mechanism correspond to the best fit is

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

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 observedpredicted 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 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.2 n 4 p 2

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 surfacewave spectral amplitudes of the Love and Rayleigh waves.

The surfacewave determined focal mechanism is shown here.
NODAL PLANES STK= 345.73 DIP= 80.95 RAKE= 154.66 OR STK= 79.99 DIP= 65.00 RAKE= 10.00 DEPTH = 12.0 km Mw = 4.22 Best Fit 0.8135  PT axis plot gives solutions with FIT greater than FIT90
The Pwave first motion data for focal mechanism studies are as follow:
Sta Az(deg) Dist(km) First motion BDM 83 24 eP_+ WENL 135 48 iP_C CVS 329 54 iP_C JRSC 189 59 iP_D MCCM 291 70 iP_C FARB 252 80 iP_D MNRC 346 109 eP_+ PACP 143 127 iP_C HOPS 326 144 iP_C CMB 85 154 iP_D ORV 17 189 eP_ GASB 345 198 eP_X KCC 104 258 iP_C PKD 147 262 iP_C WDC 353 297 eP_ JCC 334 360 eP_X YBH 354 425 eP_X TPH 86 432 ePn DAC 113 443 ePn MOD 19 468 eP_X
Surface wave analysis was performed using codes from Computer Programs in Seismology, specifically the multiple filter analysis program do_mft and the surfacewave radiation pattern search program srfgrd96.
The velocity model used for the search is a modified Utah model .
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 Lovewave spectral amplitudes, respectively.
These were input to the search program which examined all depths between 1 and 25 km
and all possible mechanisms.

Pressuretension axis trends. Since the surfacewave 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 Taxes 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 0180 degrees are sampled. 
Sta Az(deg) Dist(km) TPH 86 432 DAC 113 443 BMN 55 508 TPNV 100 532 WVOR 30 582 ELK 60 672 MVU 83 871 HLID 44 903 HAWA 12 964 LON 2 980 HWUT 62 993 WUAZ 102 997 AHID 57 1079 REDW 54 1128 MOOW 52 1156 LOHW 53 1159 BW06 59 1194 MSO 32 1196 MVCO 90 1206 BOZ 42 1222 LKWY 49 1227 RLMT 49 1336 RWWY 67 1343 ISCO 77 1447 SDCO 86 1463 PHWY 70 1478 EGMT 38 1506 LAO 48 1628 MNTX 109 1678 CBKS 80 1955 JCT 105 2211 KVTX 110 2537 MIAR 90 2584 NATX 97 2594 FVM 80 2773 SLM 78 2778 PVMO 83 2871 SIUC 80 2883 MPH 86 2887 OXF 87 2952 USIN 79 3012 PLAL 86 3054 BLO 76 3088 LRAL 89 3215 EGAK 343 3238 BRAL 93 3292 ACSO 73 3370 TZTN 81 3403 BLA 78 3655 MVL 72 3931 LBNH 64 4210
Since the analysis of the surfacewave radiation patterns uses only spectral amplitudes and because the surfavewave radiation patterns have a 180 degree symmetry, each surfacewave solution consists of four possible focal mechanisms corresponding to the interchange of the P and Taxes and a roation of the mechanism by 180 degrees. To select one mechanism, Pwave first motion can be used. This was not possible in this case because all the Pwave first motions were emergent ( a feature of the Pwave 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 velocity model used for the waveform fit is a modified Utah model .
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, Rradial 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 0.02 n 3 lp c 0.10 n 3 br c 0.12 0.2 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 100200 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 figures below show the observed spectral amplitudes (units of cmsec) at each station and the
theoretical predictions as a function of period for the mechanism given above. The modified Utah model earth model
was used to define the Green's functions. For each station, the Love and Rayleigh wave spectrail amplitudes are plotted with the same scaling so that one can get a sense fo the effects of the effects of the focal mechanism and depth on the excitation of each.
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files: