The time–distance graph compiled from first arrivals, but only where there is no anomalous geologic structure. It is used to calibrate travel times for a given offset range in fan-shooting refraction surveys.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。