import matplotlib.pyplot as plt from geoscilabs.seismic.SeismicRefraction import ( plotWavelet, viewTXdiagram, plotWiggleTX, makeinteractSeisRefracSurvey, makeinteractTXwigglediagram )
In the 3pt Science app, you explored the expected arrival times for refractions and reflections from a two-layer over a half-space model.
In this notebook, we will use synthetic seismic data to examine the impact of survey parameters on the expected seismic data.
In an ideal case, the source wavelet would be an impulse (ie. an instantaneous spike). However, in reality, the source energy is spread in space and in time (see the GPG: Waves and Rays). The source wavelet used for these examples is shown below.
Below, we show 3 plots:
The model used is the same as is in the lab write-up:
fig, ax = plt.subplots(1, 3, figsize=(15,6)) ax.set_title('Expected Arrival Times') ax.set_title('Clean Data') ax.set_title('Noisy Data') ax=viewTXdiagram(x0=1., dx=8, v1=400., v2=1000., v3=1500., z1=5., z2=15., ax=ax) ax=plotWiggleTX(x0=1., dx=8, v1=400., v2=1000., v3=1500., z1=5., z2=15., ax=ax) ax=plotWiggleTX(x0=1., dx=8, v1=400., v2=1000., v3=1500., z1=5., z2=15., ax=ax, noise=True) plt.show()
Consider a shot gather for seismic refraction survey, which means we have one shot (source), and multiple receivers (12). Shot location is fixed at x=0. There are two survey parameters:
In the widget below you can alter x0 or dx to change your survey setup. Run the next cell then try to change x0 and dx in the cell below that. Note that the next two cells are designed to help you visualize the survey layout. The x0 and dx parameter adjustment sliders here are not linked to the widget at the end of this notebook.
Assume that you have seismic refraction data. The structure of the earth is unknown and you may want to obtain useful information about the subsurface. We will assume that the subsurface in the survey area has a three-layer structure and that the velocities increase with depth. Thus, there can be four unknowns:
Based on the above information, we may expect to have up to four arrivals at a geophone, related to
The widget below will allow you to estimate the layer depths and velocities. The parameters for the widget are: