|
| | Abstract | | The airborne gravity gradient survey is one of the efficient tools of the geothermal resources exploration. Its measurement can be done at short intervals in the short period of time over wide area and is useful for the assessment of fracture distribution. The geothermal prospecting areas are situated normally in the mountainous areas. The gravity gradient responses are proportional to the product of the third power of the reciprocal of the distance between the measurement point and the anomalous mass, and therefore are affected greatly by both the steep topography and the changes of thickness and density of surface layer due to the hydrothermal alterations, intrusions, lava deposits etc. The new approach, namely the horizontal gravity gradient stack (HGGS), is proposed for the assessment of surface density, and the method is applied with the filtering the horizontal gravity gradient data (Data). The comparison between the HGGS filtered acquired Data and the equivalent calculated response of DEM based surface layer is analyzed for calculation of the surface average density by the moving window correlation (MWC) methods. Its application to the actually acquired Data around the Ogiri geothermal plant in the western Japan is analyzed, and its results fit adequately well for the existing hydrothermal alteration zones as the low surface density area, and the possible prominent distributions of intrusions and lava as the high surface density area. |
|
|
|
| |
|