Application of seismic refraction method to identify rock layers around the lake body in Jakarta, Indonesia

The objective of this study was to identify the lithological layer around the lake body to determine the ability of the reservoir body structure to withstand surrounding seepage water. This research was conducted using the MAE X820S seismic instrument, carried out on a 46-meter-long track and 24 geophones. Seismic refraction processing is done by picking at the first break in each seismic trace. From the picking results, distance and time parameters will be obtained so that a seismic velocity model can be generated to be analyzed for lithological types based on the P-wave velocity. The results of the processing show that this research area consists of two rock layers. The range of P wave velocity owned by the first layer at a depth of 0-19 m is 648.11 m/s, interpreted as sand-gravel. The range of P wave velocity owned by the first layer at a depth of 19-30 m is 1553.21 m/s, interpreted as a layer of clay. Rock layers that have a sand-gravel lithology have the ability to seep or pass water, while layers that have a clay lithology cannot pass water. Therefore, the first layer is thought to have a less strong ability to withstand surrounding seepage water.