Open source seismic refraction processing What I am in search of is an open source tool to pick first arrivals, plot travel-time curves, and perform simple velocity modeling. 

I am experimenting with seismic refraction to identify shallow subsurface interfaces. This includes the water table in a sand channel and the sand/bedrock contact. 

I have a 24 channel Seistronix RAS-24 for field acquisition. This includes a field computer with software to set geometry, run the survey, and record data to various .seg formats. 

What I do not have is a reliable program to process and model my data. Thus far I have been evaluating seismograms in the field and calculating depths by hand with the text book equations. 

I am open to any freely available software solution that would allow me to interpret and visualize my field data. This includes python or matlab based packages. 

Are there any open source and community supported seismic refraction processing tools available?
There are several references to refraction tools in the Wikipedia page for free geophysics software:

https://en.wikipedia.org/wiki/Comparison_of_free_geophysics_software