2008/05/05 11:25:44 38.490 -90.420 10 2.7 Missouri
A good location is possible because of the ANSS instrumentation near the event. We located the earthquake using hand-picked arrival times and two models, the UPLAND and HAM with the following results:
CHOOSE VELOCITY MODEL
TELE = Model( 1) P S
BEAM = Model( 2) P
HALF = Model( 3) P S
CUS = Model( 4) P S
UPL = Model( 5) P S Lg
EMBN = Model( 6) P Ps Sp S
HAM = Model( 7) P S Lg
WHICH MODEL ? 1 - 7
7
STA IWT ARRIVAL TIME PhIDQL PHASE FM CHAN
BVIL 2 20080505112551.685 1 0 e P X Z
BVIL 0 20080505112557.485 2 0 i S X Z
CCM 0 20080505112558.347 1 0 i P D Z
CCM 2 20080505112608.391 2 0 e S X Z
EDIL 0 20080505112552.807 1 0 i P + Z
EDIL 0 20080505112559.397 2 0 i S X Z
FVM 0 20080505112553.752 1 0 i P C Z
FVM 2 20080505112601.161 2 0 e S X Z
HAIL 2 20080505112613.578 1 0 e P X Z
HAIL 2 20080505112636.408 3 0 e Lg X Z
JCMO 2 20080505112550.149 1 0 e P X Z
JCMO 2 20080505112554.574 2 0 e S X Z
OLIL 0 20080505112615.285 1 0 i P D Z
OLIL 2 20080505112639.119 3 0 e Lg X Z
OLIL 2 20080505112615.349 1 0 e P X Z
OLIL 2 20080505112639.747 3 0 e Lg X Z
PBMO 2 20080505112613.421 1 0 e P X Z
PBMO 2 20080505112635.830 3 0 e Lg X Z
SCMO 2 20080505112551.150 1 0 e P X Z
SCMO 2 20080505112556.182 2 0 e S X Z
SIUC 2 20080505112621.696 2 0 e S X Z
SLM 2 20080505112549.083 1 0 e P X Z
SLM 0 20080505112553.142 2 0 i S X Z
SLM 0 20080505112549.356 1 0 i P - Z
SLM 2 20080505112553.158 2 0 e S X Z
WVIL 2 20080505112645.452 3 0 e Lg X Z
enter depth, depth < 0 is fixed at abs(depth)
10
38.6360 -90.2363 10.00 20080505112545.100 367.45
38.4443 -90.3422 13.42 20080505112544.606 25.14
38.4454 -90.3559 13.96 20080505112544.503 23.78
38.4468 -90.3575 14.51 20080505112544.475 23.14
38.4528 -90.3612 18.70 20080505112544.467 6.05
38.4759 -90.3906 23.70 20080505112544.137 1.84
38.4854 -90.4044 24.55 20080505112544.020 1.23
38.4871 -90.4065 24.67 20080505112544.002 1.21
38.4874 -90.4068 24.70 20080505112543.999 1.21
38.4875 -90.4069 24.70 20080505112543.998 1.21
38.4875 -90.4069 24.70 20080505112543.998 1.21
38.4875 -90.4069 24.70 20080505112543.998 1.21
26 phases used
STA COMP DIS(K) AZM AIN ARR TIME RES(SEC) WT QFM PHASE WGT
SLM Z 22.20 42. 136. 20080505112549.083 -0.23 2 eX P 0.33
SLM Z 22.20 42. 136. 20080505112553.142 -0.06 0 iX S 0.89
SLM Z 22.20 42. 136. 20080505112549.356 0.04 0 i- P 0.92
SLM Z 22.20 42. 136. 20080505112553.158 -0.04 2 eX S 0.46
JCMO Z 28.77 207. 129. 20080505112550.149 0.09 2 eX P 0.42
JCMO Z 28.77 207. 129. 20080505112554.574 0.08 2 eX S 0.43
SCMO Z 36.66 326. 121. 20080505112551.150 0.09 2 eX P 0.42
SCMO Z 36.66 326. 121. 20080505112556.182 -0.04 2 eX S 0.46
BVIL Z 42.22 86. 117. 20080505112551.685 -0.12 2 eX P 0.40
BVIL Z 42.22 86. 117. 20080505112557.485 -0.03 0 iX S 0.93
EDIL Z 49.12 48. 113. 20080505112552.807 0.04 0 i+ P 0.92
EDIL Z 49.12 48. 113. 20080505112559.397 0.22 0 iX S 0.68
FVM Z 55.92 182. 110. 20080505112553.752 0.02 0 iC P 0.86
FVM Z 55.92 182. 110. 20080505112601.161 0.30 2 eX S 0.26
CCM Z 87.58 237. 102. 20080505112558.347 -0.07 0 iD P 0.50
CCM Z 87.58 237. 102. 20080505112608.391 -0.57 2 eX S 0.12
SIUC Z 135.06 129. 99. 20080505112621.696 0.32 2 eX S 0.11
PBMO Z 189.68 181. 56. 20080505112613.421 -0.08 2 eX P 0.11
PBMO Z 189.68 181. 98. 20080505112635.830 -2.05 2 eX Lg 0.01
HAIL Z 190.99 115. 56. 20080505112613.578 -0.09 2 eX P 0.11
HAIL Z 190.99 115. 98. 20080505112636.408 -1.84 2 eX Lg 0.02
OLIL Z 202.85 82. 56. 20080505112615.285 0.10 0 iD P 0.20
OLIL Z 202.85 82. 97. 20080505112639.119 -2.44 2 eX Lg 0.01
OLIL Z 202.85 82. 56. 20080505112615.349 0.17 2 eX P 0.09
OLIL Z 202.85 82. 97. 20080505112639.747 -1.81 2 eX Lg 0.02
WVIL Z 229.21 91. 97. 20080505112645.452 -3.49 2 eX Lg 0.01
Error Ellipse X= 0.3481 km Y= 0.5123 km Theta = 45.3749 deg
RMS Error : 0.055 sec
Travel_Time_Table: HAM
Latitude : 38.4875 +- 0.0039 N 0.4391 km
Longitude : -90.4069 +- 0.0050 E 0.4369 km
Depth : 24.70 +- 0.78 km
Epoch Time : 1209986743.998 +- 0.09 sec
Event Time : 20080505112543.998 +- 0.09 sec
HYPO71 Quality : BA
Gap : 89 deg
CHOOSE VELOCITY MODEL
TELE = Model( 1) P S
BEAM = Model( 2) P
HALF = Model( 3) P S
CUS = Model( 4) P S
UPL = Model( 5) P S Lg
EMBN = Model( 6) P Ps Sp S
HAM = Model( 7) P S Lg
WHICH MODEL ? 1 - 7
5
STA IWT ARRIVAL TIME PhIDQL PHASE FM CHAN
BVIL 2 20080505112551.685 1 0 e P X Z
BVIL 0 20080505112557.485 2 0 i S X Z
CCM 0 20080505112558.347 1 0 i P D Z
CCM 2 20080505112608.391 2 0 e S X Z
EDIL 0 20080505112552.807 1 0 i P + Z
EDIL 0 20080505112559.397 2 0 i S X Z
FVM 0 20080505112553.752 1 0 i P C Z
FVM 2 20080505112601.161 2 0 e S X Z
HAIL 2 20080505112613.578 1 0 e P X Z
HAIL 2 20080505112636.408 3 0 e Lg X Z
JCMO 2 20080505112550.149 1 0 e P X Z
JCMO 2 20080505112554.574 2 0 e S X Z
OLIL 0 20080505112615.285 1 0 i P D Z
OLIL 2 20080505112639.119 3 0 e Lg X Z
OLIL 2 20080505112615.349 1 0 e P X Z
OLIL 2 20080505112639.747 3 0 e Lg X Z
PBMO 2 20080505112613.421 1 0 e P X Z
PBMO 2 20080505112635.830 3 0 e Lg X Z
SCMO 2 20080505112551.150 1 0 e P X Z
SCMO 2 20080505112556.182 2 0 e S X Z
SIUC 2 20080505112621.696 2 0 e S X Z
SLM 2 20080505112549.083 1 0 e P X Z
SLM 0 20080505112553.142 2 0 i S X Z
SLM 0 20080505112549.356 1 0 i P - Z
SLM 2 20080505112553.158 2 0 e S X Z
WVIL 2 20080505112645.452 3 0 e Lg X Z
enter depth, depth < 0 is fixed at abs(depth)
10
38.6360 -90.2363 10.00 20080505112545.103 378.57
38.4385 -90.3489 13.31 20080505112544.576 23.45
38.4456 -90.3628 13.71 20080505112544.489 22.33
38.4475 -90.3650 14.09 20080505112544.466 22.01
38.4515 -90.3682 15.91 20080505112544.581 6.28
38.4722 -90.3975 19.23 20080505112544.359 2.93
38.4814 -90.4047 20.95 20080505112544.220 2.06
38.4844 -90.4074 22.05 20080505112544.152 1.84
38.4855 -90.4078 22.63 20080505112544.112 1.77
38.4859 -90.4078 22.83 20080505112544.097 1.75
38.4860 -90.4077 22.90 20080505112544.092 1.75
38.4860 -90.4077 22.93 20080505112544.090 1.74
26 phases used
STA COMP DIS(K) AZM AIN ARR TIME RES(SEC) WT QFM PHASE WGT
SLM Z 22.37 42. 131. 20080505112549.083 -0.20 2 eX P 0.35
SLM Z 22.37 42. 131. 20080505112553.142 0.05 0 iX S 0.90
SLM Z 22.37 42. 131. 20080505112549.356 0.07 0 i- P 0.87
SLM Z 22.37 42. 131. 20080505112553.158 0.07 2 eX S 0.44
JCMO Z 28.59 208. 123. 20080505112550.149 0.12 2 eX P 0.40
JCMO Z 28.59 208. 123. 20080505112554.574 0.20 2 eX S 0.35
SCMO Z 36.76 326. 114. 20080505112551.150 0.05 2 eX P 0.46
SCMO Z 36.76 326. 114. 20080505112556.182 -0.06 2 eX S 0.45
BVIL Z 42.30 86. 110. 20080505112551.685 -0.19 2 eX P 0.35
BVIL Z 42.30 86. 110. 20080505112557.485 -0.09 0 iX S 0.84
EDIL Z 49.29 48. 105. 20080505112552.807 -0.07 0 i+ P 0.88
EDIL Z 49.29 48. 105. 20080505112559.397 0.09 0 iX S 0.84
FVM Z 55.75 182. 101. 20080505112553.752 -0.06 0 iC P 0.79
FVM Z 55.75 182. 101. 20080505112601.161 0.23 2 eX S 0.30
CCM Z 87.43 237. 94. 20080505112558.347 -0.16 0 iD P 0.42
CCM Z 87.43 237. 94. 20080505112608.391 -0.68 2 eX S 0.10
SIUC Z 135.01 129. 92. 20080505112621.696 0.35 2 eX S 0.10
PBMO Z 189.52 181. 54. 20080505112613.421 0.80 2 eX P 0.04
PBMO Z 189.52 181. 97. 20080505112635.830 -2.03 2 eX Lg 0.01
HAIL Z 190.99 115. 54. 20080505112613.578 0.78 2 eX P 0.04
HAIL Z 190.99 115. 97. 20080505112636.408 -1.87 2 eX Lg 0.02
OLIL Z 202.94 81. 54. 20080505112615.285 1.02 0 iD P 0.06
OLIL Z 202.94 81. 97. 20080505112639.119 -2.50 2 eX Lg 0.01
OLIL Z 202.94 81. 54. 20080505112615.349 1.08 2 eX P 0.03
OLIL Z 202.94 81. 97. 20080505112639.747 -1.87 2 eX Lg 0.01
WVIL Z 229.28 91. 96. 20080505112645.452 -3.55 2 eX Lg 0.01
Error Ellipse X= 0.4109 km Y= 0.5958 km Theta = 44.4058 deg
RMS Error : 0.079 sec
Travel_Time_Table: UPL
Latitude : 38.4860 +- 0.0046 N 0.5099 km
Longitude : -90.4077 +- 0.0059 E 0.5137 km
Depth : 22.94 +- 1.15 km
Epoch Time : 1209986744.090 +- 0.10 sec
Event Time : 20080505112544.090 +- 0.10 sec
HYPO71 Quality : BA
Gap : 89 deg
The two locations are within one kilometer of each other, and the depths are within 2 km. The HYPO71 Qualith of BA indicates good azimuthal coverage and a good distribution of take-off angles.
USGS Felt map for this earthquake
SLU Moment Tensor Solution
2008/05/05 11:25:44 38.490 -90.420 10 2.7 Missouri
Best Fitting Double Couple
Mo = 1.68e+20 dyne-cm
Mw = 2.75
Z = 19 km
Plane Strike Dip Rake
NP1 359 64 146
NP2 105 60 30
Principal Axes:
Axis Value Plunge Azimuth
T 1.68e+20 41 320
N 0.00e+00 49 146
P -1.68e+20 3 53
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.87e+18
Mxy -1.27e+20
Mxz 5.94e+19
Myy -6.78e+19
Myz -5.94e+19
Mzz 7.27e+19
########------
#############---------
#################-----------
###################-----------
####### ############---------- P
######## T ############----------
######### #############-------------
##########################--------------
##########################--------------
---########################---------------
----#######################---------------
------######################--------------
---------##################---------------
-----------###############--------------
---------------###########------------##
----------------------###------#######
-----------------------#############
----------------------############
-------------------###########
------------------##########
--------------########
---------#####
Harvard Convention
Moment Tensor:
R T F
7.27e+19 5.94e+19 5.94e+19
5.94e+19 -4.87e+18 1.27e+20
5.94e+19 1.27e+20 -6.78e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20080505112544/index.html
|
STK = 105
DIP = 60
RAKE = 30
MW = 2.75
HS = 19.0
The waveform inversion is preferred. There event was too small to be able to use the surface-wave technique. rather than using the CUS model, the HAM model (Herrmann, R. B., and C. J. Ammon (1997). Faulting parameters of earthquakes in the New Madrid, Missouri region, Engineering Geology 46, 299-311.) was used for the high-frequency synthetics since it was based on modeling the September 26, 1990 Hamburg, Missouri earthquake. Note the depth of this earthqauke is 20 -22 km, deeper than most in the region.
The following compares this source inversion to others
SLU Moment Tensor Solution
2008/05/05 11:25:44 38.490 -90.420 10 2.7 Missouri
Best Fitting Double Couple
Mo = 1.68e+20 dyne-cm
Mw = 2.75
Z = 19 km
Plane Strike Dip Rake
NP1 359 64 146
NP2 105 60 30
Principal Axes:
Axis Value Plunge Azimuth
T 1.68e+20 41 320
N 0.00e+00 49 146
P -1.68e+20 3 53
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.87e+18
Mxy -1.27e+20
Mxz 5.94e+19
Myy -6.78e+19
Myz -5.94e+19
Mzz 7.27e+19
########------
#############---------
#################-----------
###################-----------
####### ############---------- P
######## T ############----------
######### #############-------------
##########################--------------
##########################--------------
---########################---------------
----#######################---------------
------######################--------------
---------##################---------------
-----------###############--------------
---------------###########------------##
----------------------###------#######
-----------------------#############
----------------------############
-------------------###########
------------------##########
--------------########
---------#####
Harvard Convention
Moment Tensor:
R T F
7.27e+19 5.94e+19 5.94e+19
5.94e+19 -4.87e+18 1.27e+20
5.94e+19 1.27e+20 -6.78e+19
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20080505112544/index.html
|
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:
transfer from none to none freqlimits 0.25 0.30 1 2The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 1.0 175 20 -80 2.08 0.2028
WVFGRD96 2.0 255 25 10 2.14 0.1613
WVFGRD96 3.0 295 35 45 2.32 0.1081
WVFGRD96 4.0 195 55 15 2.39 0.0750
WVFGRD96 5.0 185 60 5 2.55 0.1226
WVFGRD96 6.0 255 50 -50 2.68 0.1927
WVFGRD96 7.0 260 60 -50 2.69 0.2426
WVFGRD96 8.0 260 65 -45 2.69 0.2554
WVFGRD96 9.0 260 70 -45 2.69 0.2743
WVFGRD96 10.0 260 70 -45 2.70 0.2821
WVFGRD96 11.0 260 70 -50 2.72 0.2694
WVFGRD96 12.0 195 45 40 2.79 0.2675
WVFGRD96 13.0 270 80 -45 2.76 0.2710
WVFGRD96 14.0 65 50 -60 2.87 0.4321
WVFGRD96 15.0 65 45 -60 2.85 0.4260
WVFGRD96 16.0 65 40 -65 2.83 0.4171
WVFGRD96 17.0 90 85 -25 2.73 0.4177
WVFGRD96 18.0 105 65 30 2.74 0.5757
WVFGRD96 19.0 105 60 30 2.75 0.6555
WVFGRD96 20.0 110 55 30 2.77 0.6072
WVFGRD96 21.0 110 60 35 2.78 0.6475
WVFGRD96 22.0 110 60 30 2.79 0.6345
WVFGRD96 23.0 110 65 35 2.80 0.6332
WVFGRD96 24.0 110 65 35 2.80 0.6339
WVFGRD96 25.0 110 60 35 2.78 0.6085
WVFGRD96 26.0 115 55 40 2.78 0.6348
WVFGRD96 27.0 115 50 40 2.77 0.5899
WVFGRD96 28.0 115 50 40 2.77 0.5938
WVFGRD96 29.0 115 55 40 2.78 0.6223
The best solution is
WVFGRD96 19.0 105 60 30 2.75 0.6555
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
transfer from none to none freqlimits 0.25 0.30 1 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. |
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.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureas of Mines, UC Berkely, Caltech, UC San Diego, Saint L ouis University, Universityof Memphis, Lamont Doehrty Earth Observatory, Boston College, the Iris stations and the Transportable Array of EarthScope.
The CUS used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 1990 Hamburg - CCM waveform model ISOTROPIC KGS FLAT EARTH 1-D CONSTANT VELOCITY LINE 08 LINE 09 LINE 10 LINE 11 H Vp Vs Rho Qp Qs EtaP EtaS FrefP FrefS 1.00000 4.93730 2.85063 2.48621 0.0050 0.010 0.0 0.0 1.0 1.0 2.00000 5.76166 3.32659 2.65233 0.0005 0.001 0.0 0.0 1.0 1.0 2.00000 6.25036 3.60875 2.77511 0.0005 0.001 0.0 0.0 1.0 1.0 3.00000 6.13773 3.54372 2.74132 0.0005 0.001 0.0 0.0 1.0 1.0 3.00000 6.23542 3.60013 2.77063 0.0005 0.001 0.0 0.0 1.0 1.0 4.00000 6.41363 3.70302 2.82409 0.0005 0.001 0.0 0.0 1.0 1.0 4.00000 6.36432 3.67455 2.80930 0.0005 0.001 0.0 0.0 1.0 1.0 5.50000 6.58451 3.80168 2.87197 0.0005 0.001 0.0 0.0 1.0 1.0 5.50000 6.53322 3.77207 2.85864 0.0005 0.001 0.0 0.0 1.0 1.0 5.50000 6.74437 3.89398 2.91354 0.0005 0.001 0.0 0.0 1.0 1.0 5.50000 6.63982 3.83362 2.88635 0.0005 0.001 0.0 0.0 1.0 1.0 1.25000 7.33234 4.23346 3.08635 0.0005 0.001 0.0 0.0 1.0 1.0 1.25000 7.36506 4.25234 3.09682 0.0005 0.001 0.0 0.0 1.0 1.0 2.50000 7.76689 4.48435 3.23074 0.0005 0.001 0.0 0.0 1.0 1.0 2.50000 7.84198 4.52770 3.25627 0.0005 0.001 0.0 0.0 1.0 1.0 5.00000 7.87842 4.54874 3.26866 0.0005 0.001 0.0 0.0 1.0 1.0 2.50000 8.06097 4.65414 3.33195 0.0005 0.001 0.0 0.0 1.0 1.0 2.50000 8.06097 4.65414 3.33195 0.0005 0.001 0.0 0.0 1.0 1.0
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
DATE=Mon May 5 19:07:27 CDT 2008