No abstract

The mineral content of asphalt rocks located in Buton Island (southeast Sulawesi, Indonesia) had remained unknown/unexplored despite the economic importance that may be attached to it. In order to characterize it, evaluation of the natural asphalt rock using xray fluorescence analysis (XRF) and resistivity survey have been carried out. For the XRF analysis, two rock samples were collected from the study area and analyzed at different temperatures in order to observe the variations in concentration and composition of rock samples. Vertical stacking technique (VerStack) was used for the characterization of rock sample into elements with either similar or different patterns at varying depths. The results obtained show 15 elements which are previously unexplored, and some of these elements constitute the innate elements in the parent rock minerals. The VerStack technique indicated that the characteristics of upper rock minerals (topsoil) are similar in patterns with bottom rock minerals. The radial plotting technique was also carried out and it shows good correlation with VerStack patterns. More detail geophysical investigation is recommended to ascertain the quantity of these elements identified by this study.

This study reviews the correlation between the experimental Rayleigh dispersion curve and the Vp & Vs ground model versus depth. Six samples of stations A , B , C , D , E and F were used in the experiment.The geophone spacing used was set 1 m and total length of each line was 23 m. The result shows positive significance (best fit) of R2 that ranges from 0.80 to 0.90. The fk (frequency-wave number method) dispersion curves analysis confirmed that the soil structure investigated is divided into three zones: (1) Unsaturated soil zone (clay soil), in which the layer is dominated by soil with typically alluvial clayey silt and sand. The Vp ranges from 240 m/s to 255 m/s at a depth of 2 to 8 m. (2) The intermediate zone (stiff soil), in which the layer is dominated by sand, silt, clayey sand, sandy clay and clay of low plasticity. This structure is interpreted as partially saturated soil zone, the soil is typically very dense. It contains soft rock typically fill with cobble, sand, slight gravel and highly weathered at depth of 18 to 30 m with Vp of 255 to 300 m/s. (3) Saturated soil zone at a depth of 8 to 18 m with Vp of 300 to 390 m/s. There is a very good agreement between wave-number (k) and phase velocity (Vw) produced. Both the two parameters shows similar pattern in the topsoil and subsurface layer, which constitute boundary field of soil structure. Moreover, relationship between phase velocity versus wave-length shows best fit of model from inversion with measured value (observed) in implementation of the boundary and depth of each layer.