USGS Felt map for this earthquake
USGS Felt reports page for Central US
2003/12/29 09:02:08 38.13N 90.18W 5.0 3.0 ILLINOIS USGS
Location using ELOCATE and CUS model with fixed depth of 10 km
STA COMP DIS(K) AZM AIN ARR TIME RES(SEC) WT QFM PHASE WGT FVM Z 27.34 227. 110. 20031229090214.322 -0.18 0 Eo P 0.72 FVM Z 27.34 227. 110. 20031229090218.110 0.06 0 Eo S 0.89 JCMO Z 40.60 287. 72. 20031229090215.820 -0.75 0 Eo P 0.32 SLM Z 54.02 356. 72. 20031229090225.411 0.15 0 Eo S 0.70 SLM Z 54.02 356. 72. 20031229090218.597 -0.07 0 Eo P 0.80 CCM Z 92.35 264. 72. 20031229090236.258 0.64 0 Eo S 0.20 CCM Z 92.35 264. 72. 20031229090224.862 0.20 0 Eo P 0.37 SIUC Z 98.71 119. 72. 20031229090224.718 -0.94 0 Eo P 0.14 PVMO Z 198.02 167. 48. 20031229090240.604 0.18 0 Eo P 0.18 USIN Z 222.73 95. 48. 20031229090310.573 2.36 0 Eo S 0.02 USIN Z 222.73 95. 48. 20031229090243.891 0.43 0 Eo P 0.11 UTMT Z 233.11 149. 48. 20031229090312.553 2.13 0 Eo S 0.02 PLAL Z 399.88 151. 48. 20031229090305.649 0.45 0 Eo P 0.06 Error Ellipse X= 1.1297 km Y= 1.6529 km Theta = 9.7920 deg RMS Error : 0.221 sec Travel_Time_Table: CUS Latitude : 38.1510 +- 0.0103 N 1.1482 km Longitude : -90.1969 +- 0.0189 E 1.6401 km Depth : 10.00 +- 2.71 km Epoch Time : 1072688529.659 +- 0.21 sec Event Time : 20031229090209.659 +- 0.21 sec
The focal mechanism was determined using broadband seismic waveforms. The location of the event and the station distribution are given in Figure 1.
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NODAL PLANES
STK= 129.99
DIP= 69.99
RAKE= 34.99
OR
STK= 26.53
DIP= 57.39
RAKE= 156.04
DEPTH 11.0 km
Mw = 3.00
Body wave analysis was performed using codes from Computer Programs in Seismology, specifically the wvfgrd96 waveform mtch program
Digital data were collected, instrument response removed and traces converted
to Z, R an T components.
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| Best mechanism fit as a function of depth. The preferred depth is given above. The sharp jump in fit is related to a lyeer boundary in the model at a depth of 10.0 km and the fact that the synthetics are fit at high frequencies, which means that the goodness of fit depends on matching distinct arrivals. |
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| Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to the Love and Rayleigh wave radiation patterns. The 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 P-wave first motion data for focal mechanism studies are as follow:
Sta Az(deg) IO Dist(km) P-first motion FVM 227 110 27 e- SLM 356 72 54 I+ CCM 264 72 92 I- USIN 95 48 222 e+ SIUC 119 72 98 e+
The fits to the waveforms with the given mechanism are show below:
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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 0.10 3 lp c 0.40 3
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 figures below show the observed spectral amplitudes (units of cm-sec) at each station and the theoretical predictions as a function of period for the mechanism given above. The CUS 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.