Workshop 5 (October 29-30, 2012):

Participating Organizations:

Hydrogeodesy Tutorial (4 hours, day and time to be determined):

IGCP 565 Project Workshops

IGCP 565 Workshop 5: Water Security for Africa: Bringing Together Research, Monitoring, and Managing

October 29-30, 2012
Johannesburg, South Africa

Hydroseismicity and (hydro)geodetic monitoring for Southern African water and energy development

Chris Hartnady
Umvoto Africa (Pty) Ltd, Muizenberg, South Africa

Hydroseismicity refers generally to earthquakes triggered by fluid-pressure changes in a poro-elastic crust. Introduced to explain some intraplate earthquakes, the concept is based upon the spatial correlation between: 1) crustal volumes of high seismicity (e.g., the New Madrid zone, USA); 2) large gravity-driven river basins that can provide adequate supply of water to upper- and mid-crust; and 3) a permeable crust that is tectonically stressed close to failure. The ambient tectonic condition of 'steady-state failure equilibrium' and permeability to fluid flow throughout the brittle-fracture regime (< 15 km) renders the crust susceptible to hydroseismicity of both natural (precipitation-triggered) and human-induced (injection- or extraction-triggered) origin.

Southern Africa is marginal to the propagating Nubia-Lwandle (NU-LW) plate boundary and the Cape Fold Belt and southern Karoo Basin lie within the fringe of a huge crustal shear-stress anomaly, formed where the NU-LW boundary breaks through Early Cretaceous oceanic lithosphere. Karoo Basin areas prospective for shale-gas development may therefore be especially vulnerable to large hydro-triggered earthquakes and require a cautious approach to energy exploration. Earthquakes induced by energy technologies include tremors related to hydraulic fracturing ('fracking'), larger events due to waste-water disposal by injection well, enhanced oil- or gas recovery (EO/GR), enhanced-geothermal-system (EGS) technologies, hydro-electric reservoir impoundment , and potentially also carbon capture and storage (CCS) development in deep saline aquifers.

Prior geoscientific research is needed for the efficient regulation of shale-gas and other energy developments and for concurrent protection of water resources. A research focus on hydrogeological, geothermal, seismological, geodynamic (stress & strain) objectives over a range of energy technologies should incorporate modern Global Geodetic Observing System (GGOS) methods. Taking advantage of and locally augmenting existing TrigNet GPS infrastructure, combined GNSS, InSAR and micro-gravity systems and protocols are highly suitable for monitoring of: 1) deep groundwater exploration and extraction; 2) shale-gas drilling, fracking and development operations; 3) wastewater disposal by injection-well technology; 4) carbon-capture-and-storage (CCS) development in deep saline aquifers; 5) coal-bed methane and underground coal gasification (UCG) development, and 6) envisaged large-scale water-supply and hydro-electric power schemes.

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