Electronic Theses and Dissertation

Identification of shallow subsurface structures on geothermal field of ie jue, seulawah agam using seismic refraction method abstract subsurface geological structures in geothermal area are very fundamental to know before the geothermal field is exploited. map of the subsurface will provide information about physical condition distribution of geothermal field such as the presence of fractures / fault, lithology and other critical elements of a geothermal system. therefore, to determine the geothermal subsurface structures of seulawah agam then we conducted a research using seismic refraction method in geothermal field of ie jue, aceh besar regency. seismic refraction method was used to identify shallow subsurface structures based on compressional wave velocity value (compressional p-wave velocity, vp). the data of p-wave velocity were acquired and recorded using pasi 16s24-p seismograph where the seismic wave being triggered by an impact of sledge hammer and detected by arrays of detector devices called geophones. a total of four seismic lines were used in two locations near geothermal manifestation area of ie jue. to obtain the resolution of subsurface interfaces, 9 shots points were utilized symmetrically along the length of each line and energy source positions at far offset generally were set at 30 – 50 meter from the ends of a 3 meters spacing geophone array. zondst2d software was used to process the seismic data which produce 2 dimensional (2d) velocity models of subsurface profil for each seismic line. based on the velocity model results, we can identify there are three layers of subsurface geomaterial consisting of: top soil which is at 0 – 10 meter depth and has vp values 0,4 – 0,8 km/s (400 m/s – 800 m/s); clay which is at 5 – 25 meter depth and has vp values 1,0 – 2,2 km/s (1000 m/s – 2200 m/s); and sandstone which is 15 meter downwards and has vp values above 2,5 km/s (> 2500 m/s). the subsurface profiles which have been obtained also revealed that the weak zone occurrence presumed as a fracture zone in line l3. keywords: seismic refraction, subsurface structures, geothermal field, zondst2d, ie jue, aceh besar.