陸から海に至るビッグデータ探査技術－海洋底資源から陸上地熱資源まで－

[1301-12-09] Detecting groundwater potential in crystalline basement in central Mozambique by lineament distribution and transient electromagnetic resistivity

^○Luis A Magaia¹, Tadanori Goto¹, Alaa A Masoud², Katsuaki Koike¹ (1. Kyoto University, 2. Tanta University)

司会: 柏谷公希（京都大学）

Keywords:Groundwater, Lineament, Transient electromagnetic method, Resistivity, Mozambique

Groundwater resource is crucial in African countries for agriculture, industry, and drinking. To detect high potential zones of groundwater and understand geological structures controlling the potentiality, we combine lineament analysis and the transient electromagnetic method (TEM) by selecting a central part of Mozambique mainly covered by Precambrian gneiss as a case study. Gridded data from Shuttle Radar Topographic Mission Digital Elevation Model (SRTM DEM) is enhanced using the adaptive-tilt multi-directional shading technique and lineaments are extracted from it using a non-filtering technique, Segment Tracing Algorithm (STA). Next, TEM line are set across the continuous lineaments with dominant trend, NNW, which are regarded to be aligned along the inferred faults in different geological settings from a geological map. The TEM survey consists of the TEM-FAST 48HPC system with a single square coincident loop of 20 by 20 m². Along the lines, 2D resistivity distributions are modeled from the 1D resistivity columns by the inversion analysis at each TEM site and the connection of adjacent columns. Apparent resistivity curves with various characteristics are observed along the lines, which highlights lateral discontinuities of resistivity. In general, resistivities decline and become lower than 80 Ωm in the middle lineament zones and tend to increase with increasing of distance from the zones to be higher than 100 Ωm. This contrast is probably caused by the degree of weathering along the fracture zone and therefore, intense weathering is a control factor of groundwater occurrence. However, the effect of lineament is not evident in some lines. We try to include the vegetation index from optical sensor image as an auxiliary information on shallowness and richness of groundwater.