Developing low-cost frequency-domain electromagnetic and induced polarization geophysical instrumentation

Abstract

Climate change, expanding populations, and the rapid industrialization of low and middle income countries have created unprecedented challenges for local communities and their surrounding environments. Near-surface geophysical surveying can provide a wealth of data to help address these challenges in a cost-effective manner that is minimally invasive to local environments. Electrical and electromagnetic methods are two such families of techniques that are widely used in near-surface geophysics due to their wide applicability to near-surface problems, such as water exploration and environmental monitoring, the ease of data acquisition, and that electrical and electromagnetic geophysical data can greatly aid near-surface investigations with minimal processing. Recent development and the widespread availability of electrical components and cheap microcomputers have created new opportunities for developing purpose-built, low-cost, open-source geophysical instrumentation for near-surface investigation. This thesis reports the development of two such prototype instruments. First, a frequency-domain instrument that is capable of sensing conductive objects in near-surface environments and costing under US$400 has been designed and validated at the Colorado School of Mines. Second, a time-domain induced polarization instrument, based off an existing low-cost direct current resistivity meter system, was developed and validated in a laboratory setting. The induced polarization system is capable of sensing highly chargeable objects, such as sulfides, and costs under US$200 to construct. Both instruments have demonstrated the capability to be leveraged for near-surface humanitarian applications. Future development includes improving on the mechanical stability of the low-cost instrumentation and improving autologging capabilities for use in remote and time-lapse geophysical investigations.