"Seismic" by frockland

When I finished my studies as a social worker there were no jobs available and I was unemployed for a couple of weeks. To earn some money I went on a nearby operating seismic crew and ask for work. All I needed was a driving licence, accept the lousy salary - and I was employed. Until that day I didnīt know that such a business like Seismic existed and for sure I didnīt know what I had t expect.

Laying cables, planting Geophones and later picking it all up again was my job. Not very interesting or difficult but if you need to earn some money? More interesting were the other guys I was working with. Usually everybody was accepted as long as they were in physically good shape and not too obvious drunken or drug addicted. (This changed 100% in the meantime), but to make a long story short - after some month I started to like business and stayed in Seismic for nearly 10 years. Luckily I got more interesting jobs than picking up phones or changing cables. During the late 90s when the Seismic data exploration business got into a crisis I was working as a Social worker with all social security one can have but after 3 years I realised that I still had this virus of Seismic in me and took the offer to work in Iran. So I quit my 9-2-5 job and left everything behind.

One of my colleagues always said: "Seismic is not an attitude - but a state of mind!" You travel to some places you would never go, do all the things your parents were giving you a bollocking for when you were younger, like "playing" with heavy machinery, being covered in mud and having non scheduled days were no day is like the previous! It`s like travelling: Either you like it or you don`t like it - but there is nothing in-between!

For some basic understanding I will give a small explanation of Seismic exploration works:
Seismic methods of subsurface evaluation involve directing an intense sound source into the ground and spreading receivers called geophones, analogous to microphones, across the ground. The receivers pick up "echoes" that come back up from the ground and record the intensity and time of the "echo" on computers. Complicated data processing is done to turn these signals into images of the geologic structure in the ground.

There are two types of "echoes" produced as the sound waves travel into the ground. "Reflected" waves are just that waves which travel downward, bounce off a layer or object in the soil or rock and return to the surface. "Refracted" waves are ones which travel downward then turn at a geologic boundary, such as the surface of a rock layer, and travel along it before returning back to the surface.

By their nature, reflected waves have the ability to show more detail about the geology below the ground; however, the complex physics resulting from multiple "echoes" can make reflections very difficult to interpret. Refracted waves are most typically used to determine information such as the nature of the surface of shallow bedrock (e.g., rock less than 100 feet below the ground). Seismic reflection surveys have historically been valuable tools in the exploration for oil since they can provide a wealth of information about deep rock structures. Seismic refraction surveys are more suitable for shallow exploration and definition of geologic surfaces, such as bedrock or the water table.

At first a mission needs to survey profile lines where a look into the subsurface is wanted. This is done by surveyors, flagging out lines. This can be done by different methods but it?s usually done by satellite navigation systems.

On these lines cables and geophones were laid to measure the reflections that were coming up after energy was sent into the ground. There are different energy sources: Most common are dynamite explosions or vibrator trucks shaking the ground but also a dropping weight, a sledge hammer or air guns can be used, depending on the required data and environment. It?s possible to look some 1000 meters deep into subsurface.

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