No abstract

The analysis of shear wave velocity on rocks in Watatu, South of Banawa, Donggala Regency using Microtremor Refraction Method (ReMi) has been conducted. The purpose of this research is to analyze the propagation velocity of shear wave on rocks layers up to 30 m in depth and to know the type of rock layer profiles in the study location. The method used was Microtremor Refraction using Surface Wave Analysis Wizard software and WaveEq software. The results showed that the rocks of trajectory 1 and trajectory 3 were classified into type E soft soil type with the respective including Vs30 values of 127.8 m/s for trajectory 1 and 98.9 m/s for trajectory 3. Then for trajectory 2 and trajectory 4 are classified into D type rocks i.e medium soil types with Vs30 values respectively on Track 2 of 235.1 m / s and for Lane 4 of 196.9 m/s.

Rock Porosity Estimation Research Using Refraction Seismic Waves in Bora Village, Sigi Regency has been conducted. The purpose of this study was to determine the distribution of porosity of shallow subsurface rocks at geothermal locations. Data is collected on 6 different trajectories using ES-3000 to get a picture of subsurface waves. The data processing method uses Seisimager software to get a cross-section of the wave velocity and Rockwork software to get a cross-section of the porosity of subsurface rocks. The results showed different rock porosity values for each trajectory. Rock porosity values obtained at track 1 to track 6 are in the range of 27.1% to 30.5%. All trajectories are on a special porosity scale which means they have a large porosity volume as a place to store fluid.

Balaesang Tanjung in Donggala Regency is a peninsula surrounded by the sea. It is considered to have limited groundwater to be used as a source of clean water. This preliminary hydrogeological study aims to estimate the groundwater potential zone in the area. The main feature based on the lowest topography and gentle slope. It is occupied by the Molasse Formation, where limestone and other deposits are characteristic of a porous lithology, which most likely allows infiltration processes to occur in this area. Of course, the presence of discontinuities in limestones can serve as secondary porosity for storing fluids. So that the delineation of groundwater recharge follows the distribution of the Molasse Formation and the morphology of the plains. From these results, we recommend that the western Balaesang Tanjung area can act as a low to moderate productive aquifer, where the flow can flow through fissures and fissures.

The earthquake of September 28, 2018, has caused changes in the structure of subsurface rocks in the Palu Valley of Central Sulawesi. Differences in rock structure occur due to deformation by seismic waves generated by the earthquake. Analysis of structural changes and strain of rock carrying surfaces is performed using the geomagnetic method. This study aims to map the fractures and local faults below the surface after the earthquake. Magnetic measurements are carried out using the Proton Precision Magnetometer with several measuring points of more than 856 stations. The measured magnetic data was corrected to obtain the total magnetic field intensity. Euler deconvolution is then performed to estimate depth and estimate subsurface, structure models. The results showed that the study area was identified by local fault and fractures below the surface, with depths ranging from 0 to 2000 meters. Local fractures and fractures formed are generally north-south trending following the Palu Koro fault.