Problem with the energy of the directed P-wave vs S-wave using SPECFEM2D

[qnstar]

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Hi all,
I am new to SPECFEM2D. I have a problem with the energy of the directed S-wave and your help is appreciated. I am running specfem2D to calculate the wave field under the assumption of a simple two-layer layered geological model using an elastic wave source (see attached parameters). I hope to obtain the stratigraphic structure by picking up multiple seismic reflection data. However, I found that the energy of S-waves has always been higher than that of P-waves in both horizontal and vertical components of seismic wave records.

Table 1. model parameters

Model num	elastic	density	Vp	Vs
1	1	2000.d0	4200.d0	2300
2	1	2200.d0	3000.d0	1500

 

According to the Seismic wave propagation theory and observation system settings, the energy of the directed P-wave in the horizontal component is strong, while the energy of the directed S-wave is weak. In the vertical component, both the direct S-wave and the reflected P-wave have strong energy.

 

The simulation results show that the energy of S-waves in the horizontal component is strong, and the energy of reflected P-waves in the vertical component is weak. The energy of reflected S-waves has always been strong compared to P-waves, which seems to be inconsistent with conventional seismic exploration simulations.

 

I hope to use a vertical force source to simulate better reflected P-wave responses. I don't know if this is a problem with setting the source parameters? This force source seems to be a horizontally applied force in the wave field, which does not seem to be the desired result for our model.

 

I would like to know how the force of the elastic force source using specfem2D works? Is it the problem with the source or the parameter settings? I look forward to your help. Thank you!

 

 

[qnstar]

DATA.zip