New Modified Design of Accelerated Weight Drop (AWD) for Shallow Seismic Survey: A Field Test, Results and Evaluations

The reflection seismic is technique to image subsurface structures to depth of thousand meters. In addition, the method is also applied to shallow targets with depths from 10 to 1000 m, for engineering problems and site investigations. Even though shallow seismic method is only scaling of reflection seismic method, problems encountered in the survey operation are not simple. Problems are cost and environmental issues, particularly related to sources used. The use of explosive seismic sources has implications for costs and environmental issues. One promising source option is an accelerated weight drop (AWD). The use of AWD as seismic source is highly dependent on surface conditions of survey area. Therefore, an AWD design that is suitable for various types of survey areas is needed. A new prototype has been developed as an improvement over previous prototype. The design modification is intended to increase penetration depth and widen frequency band of the source signal. Important criteria have been considered in AWD’s design, such as impact energy (penetration and bandwidth), repeatability, portability, economical and environmentally friendly. This paper reports performances test of prototype AWD for generating seismic sources to obtain high-quality data. The survey was conducted to test performances. There is no specific target of geological structure in areas. The survey located in a densely populated area was conducted using 100 units of wireless seismometer (5 m interval) and shot point interval of 15 m. The recorded data has been processed using a standard seismic data processing workflow. The results show that the reflected signal is visible at a depth of 50 ms to 800 ms or about 50–700 m, with a signal frequency of up to 100 Hz with good image quality. The criteria of penetration depth and frequency band have been achieved. Survey cost to obtain 0.5 km is less than 500 USD. This AWD has met other expected design criteria, economical and low environmental impact. Results are better than the old prototype and product in the market.