The Correlation Between P-Wave Velocity Value With Pathways Of Geothermal Manifestation In The Area Ie Jue, Aceh Besar As Hazardous Side Study

Abstract

Refraction seismic survey has been carried out in the manifestation area of Ie Jue, Seulawah Agam Volcano Region, Seulimuem, Aceh Besar Regency. This research aims to identify weak zones related to channel of geothermal outflow that would bring about a potential hazard for human activity and that goal is obtained by exstracting information from P-wave velocity. The data acquisition was conducted for two seismic lines located near to the geothermal manifestation area of Ie Jue. Both of the seismic lines were set up by linking the 24 geophones to the Seismograph PASI 16S and placing them in three meters spacing of each other. The offsets either left or right were laid out at 35 meters from first and last geophones, so the total spread length of each seismic line is 139 meters. The data recorded by the tool then were processed by using ZONDST2D and finally, the 2D velocity profile was obtained. The results show that the 2D velocity profiles illuminate us to potray and interpret the features figured out. The most valuable information provided by the profile is the existance of such the weak zones of the first and second seismic lines at relatively near-surface depth. These weak zones were suspected as the fractured or low-velocity zones, where their velocity ranges approximately at 0.2 - 1.2 km/sec. These low-velocity layers are strongly predicted as the pathways or channels of the geothermal fluids that appears to the surface. The shallow weak zones are potentially to become the hazard grounds because they are regularly traversed by timber trucks from which the dynamic load will be pushing them down. As consequence, the ground surfaces could gradually become a land subsidence endangering human activity within the vicinity of the area.