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Mulwa JK, Kimata F. "Determination of source parameters for the May 20, 1990 Southern Sudan earthquake by inversion of teleseismic body-waves.". In: Operating Management of Earthquake, Tsunami and Volcano Eruption Observation Systems. Nagoya: Research Center for Seismology, Volcanology and Disaster Mitigation, Nagoya University; 2011. Abstract

The May 20, 1990 earthquake which occurred in southern Sudan is so far the strongest earthquake to occur in the eastern part of African continent within the past 21 years. It caused damage in southern Sudan as well as severe shaking in parts of Uganda and Kenya, and was accompanied by aftershocks on May 24, 1990 of moment magnitudes Mw = 6.5 and 7.1.

Inversion of teleseismic body-waves has been undertaken for the purpose of this study in an attempt to reassess the seismo-tectonics of northern and central Kenya as well as southern Sudan. The results show that the best solution for the inversion of teleseismic body waves for the May 20, 1990 earthquake consists of only one event with a source mechanism of 315o/84o/-3o (strike/dip/rake) and the fault plane is characterized by left-lateral strike-slip fault mechanism. The focal depth for this earthquake is 12.1 km, seismic moment Mo = 7.65 x 1019 Nm and moment magnitude, Mw = 7.19 (7.2). The fault rupture started 15 seconds earlier and lasted for a duration of 17 seconds along a fault plane having dimensions of length  60 km and width  40 km. The average dislocation along the fault is 1.1 m and the stress drop,  is 1.63 Mpa.

The distribution of historical earthquakes from southern Sudan through central Kenya shows a NW-SE alignment of epicenters. On a local scale in Kenya, the NW-SE alignment of epicenters is characterized by earthquakes of local magnitude Ml  4.0. This NW-SE alignment of epicenters confirms the existence of an active fault zone, the Aswa-Nyangia fault zone, from southern Sudan through central Kenya and further into the Indian Ocean. However, owing to lack of waveform data for these historical earthquakes, it is not possible to determine the source mechanism of the fault. Further work on inversion of short period waveform data is required so as to precisely determine the fault mechanism of this NW-SE trending fault zone in the central and southeastern parts of Kenya.

Mulwa JK, MATHU ELIUDM. "Development of geothermal energy resources in Kenya-A collective responsibility between University and Industry.". In: Proceedings: 3rd KenGen geothermal conference. Safari Park Hotel, Nairobi, Kenya: KenGen; 2004. Abstract

Kenya is the first and so far the only country in the African continent to generate electricity from geothermal resources. Currently the power output from geothermal resources stands at about 57 MWe. This output is expected to rise with the planned commissioning of other power plants in Olkaria and elsewhere. Geothermal energy is reliable, environmentally sustainable and the least cost source of base load power for Kenya. The least cost power development plan (KPLC, 2001) has proposed that the geothermal sources provide approximately an additional 500 MWe of base load electric power over the next 20 years (Omenda, 2001; Mwangi, 2001). It should be noted that the Rift System in Kenya has a potential of producing 2000 MWe of geothermal energy that can be generated using conventional steam condensing turbines. This power generation can even exceed 3000 MWe when combined cycle and binary systems are used (Omenda, 2001). For these reasons, exploration for geothermal resources is quite active within the Kenya Rift System and the potential to be exploited is quite substantial.

Geothermal resource exploration has largely been undertaken by the Kenya Electricity Generating Company (KenGen) and the Ministry of Energy. There has also been an input from international organizations and consulting companies. Nevertheless, there has been low level contributions by the local universities in geothermal resource studies and research works. In other countries such as U.S.A, New Zealand, Iceland, Japan, Philippines, Indonesia, just to mention a few, geothermal resources have been collaboratively studied and researched on by both the university and the industry and there is no satisfactory reason why this cannot be emulated in our continent. This paper therefore outlines some of the areas where collaborative work can be undertaken by both the industry and the local universities. Some of the areas include feasibility studies, exploration, construction and installation, production, research and development. This is essential for better knowledge dissemination, improvement and training for posterity.

Mulwa JK, Mariita NO. "Dyking processes in Arus-Bogoria geothermal prospect in Kenya revealed using gravity and microseismic data.". In: 37th New Zealand Geothermal Workshop: The next 10,000 Megawatts. New Zealand: University of Auckland, New Zealand Geothermal Association; 2015. Abstract

Arus-Bogoria geothermal prospect, located in the central Kenya rift valley (KRV), encompasses several features of geological significance that are indicators of possible geothermal potential. These include surface manifestations, such as fumaroles, steam jets, mud pools, hot springs, spouting geysers, and high rate of micro-seismic activity of about 500 earthquakes recorded within a period of three months in comparison to other geothermal fields and prospects along the Kenya rift valley (KRV).

A comparison of the results of gravity survey, undertaken between 2005 and 2006 for geothermal resource evaluation of Arus and Lake Bogoria geothermal prospects, to results of micro-seismic monitoring undertaken in 1985 during the Kenya Rift International Seismic Project (KRISP 85) was undertaken to map the existence of heat source(s), presumably due to dyking, and define the brittle-ductile transition zone. The results indicate that the heat source is due to a series of north-south trending dyke injections occurring at depths of ~3 – 6 km in the vicinity of the Arus steam jets. The geothermal prospect is seismically active and approximately 95% of the seismic activity is probably associated with tectonic activity due to reactivation of north-south trending faults.

Further, only ~5% of micro-earthquakes can be correlated with the geothermal activity such as dyking, as mapped using gravity data, and hydrothermal processes. The change in seismic activity at Arus-Bogoria geothermal prospect occurs at a depth of 8 – 15 km with a peak in micro-seismic activity at 12.5 km depth. We therefore conclude that 8-15 km represents the brittle-ductile transition zone in Arus-Bogoria geothermal prospect.

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