Hammer blow seismic

The hammer blow seismic is a method of seismic with little technical effort. It is used to investigate stratifications in the subsurface close to the ground, but has only a limited range.

The vibrations of the ground triggered with a heavy hammer or with falling weights are deflected ( refracted ) or thrown back ( reflected ) by the distinctive layer boundaries . On the earth's surface , these transverse waves and shock waves are picked up by geophones that have been designed to be flat or profile-like. The registrations are forwarded by electrical cables to a measuring center, recorded and analyzed with computer programs.

Important applications are, for example, the depth measurement of glaciers and the appearance of rocks under sediments or rubble heaps . The hammer must have a minimum weight of a few kilograms and at the same time triggers the time measurement , which enables easy registration of the running times on the geophones . At short distances, the direct waves hit the laid out geophones first, but they can be overtaken by the refracted waves at the outer profile points and at greater ice or sediment depths. Because the latter run faster, the more compact the rock becomes with the depth.

In addition to the simple equipment, another advantage of the method is that it enables a simple evaluation based on the principle of refraction seismics even in the field using runtime diagrams .