Geohazard Identification Using 2-D Resistivity Imaging for Seulawah Agam Volcano, Indonesia

Abstract

Common parameter used for delineating geothermal system is resistivity. Hydrothermal alteration of primary minerals depends on temperature distribution and forms various clay minerals with conductivity properties. Clay minerals formed at high temperatures are more resistant than lower temperature. Most geothermal systems within active volcanic regions show low resistivity (1-5 Ohm.m) surrounding an inner core of higher resistivity. 2-D resistivity study conducted at Seulawah Agam active volcano and its vicinity (Aceh) with geothermal sources (Herzt, Ie Jue and Ie Seu'um) flowing from south-east to north-west. Two lines, L1 and L2 were conducted crossing the suspected geothermal flow using ABEM SAS4000 system with 10 m minimum electrode spacing and Pole-Dipole array. Resistivity results indicated two main zones; (i) top layer, <100 m depth with resistivity value of >60 Ohm.m and (ii) cap-rock, 30-100 m depth with resistivity value of 6-50 Ohm.m. Few fractures and low resistivity regions (<5 Ohm.m) were identified in the caprock. Hot water and hot mud have low resistivity value; hence the low resistivity regions were interpreted as geothermal flow and it is convincingly suspected to be a geohazard zone. New extension of Seulawah Agam geothermal flow was identified by 2-D resistivity method.