SEISMIC REFRACTION and REFLECTION

Seismic refraction is a geophysical method of obtaining an estimate of p-wave acoustical velocity of the earth’s near surface soils to depths typically less than 100 feet.  Seismic refraction surveys are commonly performed in areas where the geology is not complex or where the objective is to map the top of bedrock.

Seismic reflection is a geophysical method of obtaining structural and stratigraphic information by means of observing acoustic waves as they reflect from geologic layers.  Reflection surveys are most often performed to define complex geologic structure.

Depths of penetration for reflection surveys far exceed those of refraction survey methods.

Both methods require the use of a seismic source, geophones, and multi-channel seismic recording instruments. 

Applications

Used to map soil and sediment thickness and elevation of subsurface interfaces, such as top of bedrock.

Determine lateral continuity of soil and sediment layers.