Introduction

NetQuake accelerometers have been deployed in this area since January, 2010. The occurrence of the larger event permits a QC chack on the NetQuake recordings. The locaiton map is shown below:

The procedure is to use the WUS Green's functions with the derived source parameters for this earthquake:

     HS=14.0
     STK=120
     DIP=80
     RAKE=5
     MW=4.33

The accelerometer recordings were deconvolved to ground velocity in units of m/s. The following filter band was selected to avoid instrumental noise at low frequency and also to be at low enough frequency that hte Green's functions would not have to be recomputed:

     hp c 0.20 n 3
     lp c 1.00 n 3
     br c 0.12 0.25 n 4 p 2
Because such high frequencies were used, we also applied the gsac command
     triangle w 1.0

to the observed waveforms to account for the source time function used to make the Green's functions.

Comparison

The following figure compares the observed and predicted three component seismograms at each station. In the figure the colors red and blue correspond to the osberved and predicted traces. The columns indicate the component of ground motion. Each pair of observed-predicted traces is plotted to the same scale. The time axis is the absolute travel time from 10 seconds before to 40 seconds after the origin time.

The amplitudes and polarities agree very well.

Velocity model

The WUS model is used for this earthquake source region because the WUS model has lower velocities in the upper crust which agrees well with observations for earthquakes here.

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