Inovasi pemanfaatan peta anomali pseudogravitasi untuk interpretasi pola sebaran batuan andesit masif di desa Candiwulan kecamatan Kutasari kabupaten Purbalingga dan sekitarnya

Abstrak

The use of pseudogravity anomalous map to interpret the distribution of andesite rocks in Candiwulan Village and surrounding areas, Kutasari District, Purbalingga Regency has been carried out. The research has been conducted from April to September 2019. The materials and equipments needed consisted of the total magnetic anomalies data, personal computers (PC), and some software such as Fortran 77, Surfer 10, and Arc-GIS 3.0. The amount of the total magnetic anomalies data obtained is 142 data stretching in the geographical position of 109.2788° – 109.3072° E and 7.3032° – 7.3319° S with values ​​ranging of -1,376.79 – 2,037.26 nT. The total magnetic anomalies data are then processed through several stages in order to obtain the local magnetic anomalies data with values ​​ranging of -1,238.13 - 1,892.4 nT. The filtering is applied to the local magnetic anomalies data to reduce the magnetic effects on the surface so the new local magnetic anomalies data are obtained with values ranging of -309,321 - 770.88 nT. To localize subsurface anomalous sources, the local magnetic anomalies data both before and after filtering are transformed into the pseudogravity anomalies data. For the magnetic anomalies data before filtering, the pseudogravity anomalies data obtained have values with ranging of 75.992 – 119.498 mGal. Whereas for the magnetic anomalies data after filtering, the pseudogravity anomalies data obtained have values with ranging of -27,815 to 41,087 mGal. Interpretation results of the both pseudogravity anomalous maps indicate the presence of shallow anomalous sources distributed in the west to northwest of the research area, where the anomalous source is relative pointing downward in the western area. The anomalous sources are interpreted as andesite igneous rocks which are very massive