Stephen Alumasa Onacha, PhD

Dr. Stephen Alumasa Onacha is a highly accomplished geothermal geophysicist with more than three decades of international experience in geothermal exploration, resource assessment, and development. He is widely recognized for his strong technical expertise in applied geophysics and for pioneering advanced geophysical methods that have significantly reduced exploration risk and improved drilling success in geothermal projects in Kenya and worldwide. Dr. Onacha holds a PhD in geophysics from Duke University, where his research focused on developing and applying innovative Joint Geophysical Imaging (JGI) techniques that integrate magnetotelluric (MT) and micro-earthquake (MEQ) data to accurately identify high-productivity geothermal wells. His academic and professional training is further reinforced by specialized geothermal education from the United Nations University in Iceland and leading institutions in Europe and New Zealand. His technical competence spans geothermal geophysics, reservoir characterization, conceptual model development, well targeting, and geothermal field monitoring.

In Kenya, Dr. Onacha made major technical contributions during his long tenure at the Kenya Electricity Generating Company (KenGen), where he served as Chief Geophysicist. He led detailed geophysical exploration studies at Olkaria, Eburru, Suswa, Longonot, Menengai, Korosi, and other prospects, and successfully identified drilling targets that resulted in high-production wells, notably at the Olkaria-Domes field. His work played a critical role in updating conceptual models and supporting sustained geothermal expansion in Kenya. Internationally, Dr. Onacha has led and supported geothermal exploration projects across Africa, Europe, the Americas, and the Caribbean, including landmark work in Iceland, New Zealand, Chile, Australia, the United States, Rwanda, Zambia, Comoros, Tanzania Montserrat, and Saint Kitts and Nevis. Dr. Onacha was a consultant for GeoAlaska, LLC with respect to the development of the geothermal resources at Mt. Spurr and Augustine Island on the west side of Alaska’s Cook Inlet.  Dr. Onacha has reviewed extensive geological and geophysical data regarding each prospect. He has served as Programme Manager at the Institute of Earth Science and Engineering in New Zealand, Geothermal Development Director at Akiira Geothermal Limited and Empaaka Energy Limited, and senior geothermal consultant to governments, utilities, and private developers. For the last three years, Dr. Onacha has been part of the South-to-South Technical Cooperation (SSTC) between Kenya and Indonesia facilitated by GIZ. His work has consistently translated advanced geophysical analysis into successful drilling outcomes and bankable geothermal projects. Dr. Onacha’s career is defined by deep technical rigor, innovation in geothermal geophysics, and a proven ability to apply science to real-world geothermal development challenges leading to geothermal project development globally. Dr Onacha has been an active director of the Geothermal Association of Kenya (GAK) and the Kenya Private Sector Alliance (KEPSA) for the last six years.