# Seismic refraction in MATLAB

#### Summary

## Learning Goals

## Context for Use

## Description and Teaching Materials

The step-by-step guide to running the MATLAB scripts is in the attached file: Refraction in MATLAB (Microsoft Word 2007 (.docx) 117kB Sep24 15)

This activity requires MATLAB functions:

- refraction_2layers.m ( 1kB Sep24 15)
- refraction_3layers.m ( 3kB Sep24 15)

## Assessment

After doing this activity students should be able to explain how travel times and crossover distances change when layer thickness and velocities change. They should be able to explain why this is (e.g. the head wave spend more time traveling through a thicker top layer). They should be able to explain that if a survey does not include arrivals on either side of the crossover, it is impossible find the speeds of both layers. For a three layer system, students should be able to see that a thin middle layer may not ever be the first arriving layer, and thus may not be identified in refraction surveys. Finally, they should be able to see and explain why there are no head wave arrivals from a low velocity layer.