[en] Ultrasonic travel-time tomography using laboratory model were performed in this preliminary study. The measurement was calibrated using a known velocity laboratory model representing an iron with P-wave velocity (V_p) 5920 ms⁻¹. Source and receiver transducers were equally spaced around the model. In the first measurement, the source position was at point 1, and receivers at points 2 to 16. In the second measurement, the source position was at point 2, and receivers at points 3 to 1. The measurements were repeated, and a total of 240 ray path were recorded. Then, the travel-time data inverted and reconstructed to get tomogram using a MSIRT (Modified Simultaneous Iterative Reconstruction Technique) algorithm. Each pixel tomogram represents a point velocity at ray path intersections. It is important to have at least one intersection for each pixel, so each pixel represents an average velocity. The use of robotic instrument provides precise and efficient results in data measurements despite errors between 1% and 3% at the time of motor rotation. The ultrasonic tomography using robotics equipment proves to be helpful in obtaining accurate measurement. (paper)

[en] The development of a method to enhance resolution in imaging subsurface structural geology has continuously developed. The method of tomography field is electrical resistance tomography that is a powerful method for imaging subsurface structural geology. The electrical resistance tomography method is divided into two parts that are forward modelling and inverse modelling. The principle of forwarding modelling is to solve elliptic differential equation second order by finite volume method. The result of this part is the subsurface resistivity magnitude where it is used to model structural geology. For modelling inverse, the algorithm that has used to the model of subsurface structural geology is the Gauss-Newton method with an updated model that is preconditioning conjugate gradient. The ability of the electrical resistance tomography has tested to models of subsurface structural geology such us layering, and fault model. The results have revealed that this method able to model the subsurface of the structural geology, delineate the edge of the layer, and enhance the resolution of the model. (paper)

[en] Lembang and Cimandiri fault are active faults in West Java that thread people near the faults with earthquake and surface deformation risk. To determine the deformation, GPS measurements around Lembang and Cimandiri fault was conducted then the data was processed to get the horizontal velocity at each GPS stations by Graduate Research of Earthquake and Active Tectonics (GREAT) Department of Geodesy and Geomatics Engineering Study Program, ITB. The purpose of this study is to model the displacement distribution as deformation parameter in the area along Lembang and Cimandiri fault using 2-dimensional boundary element method (BEM) using the horizontal velocity that has been corrected by the effect of Sunda plate horizontal movement as the input. The assumptions that used at the modeling stage are the deformation occurs in homogeneous and isotropic medium, and the stresses that acted on faults are in elastostatic condition. The results of modeling show that Lembang fault had left-lateral slip component and divided into two segments. A lineament oriented in southwest-northeast direction is observed near Tangkuban Perahu Mountain separating the eastern and the western segments of Lembang fault. The displacement pattern of Cimandiri fault shows that Cimandiri fault is divided into the eastern segment with right-lateral slip component and the western segment with left-lateral slip component separated by a northwest-southeast oriented lineament at the western part of Gede Pangrango Mountain. The displacement value between Lembang and Cimandiri fault is nearly zero indicating that Lembang and Cimandiri fault are not connected each other and this area is relatively safe for infrastructure development. (paper)