Natural Earthquake Laboratory in South African Mines (NELSAM)

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

0409605 Reches This is a project to investigate seismogenic processes at the focal-depth of earthquakes. This will be conducted in the deep gold mines of South Africa that offer unique advantages: (1) Mining operations control the location, magnitude and timing of the earthquakes and the investigation can be focused at sites where earthquakes are guaranteed; (2) The mine infrastructure allows access to earthquake-producing faults and permits monitoring fault activity before, during and after earthquakes at distances of 1-100 m from the hypocenter; (3) The size of mine earthquakes (M = 3-4) bridges the gap between the small samples used in the laboratory (M<0) and large earthquakes along crustal faults (M>6); and (4) The effects of catastrophic earthquakes on subsurface life (microbial ecology) could be monitored. The South African mines are, in essence, a natural earthquake laboratory with opportunities to make fundamental contributions to earthquake science by near-field, three-dimensional monitoring of the earthquake process. There is no other natural environment where this is possible. Specifically, the project will involve: (1) Drilling through three active fault zones at depths of 1.5 - 3.0 km in mines. The faults will be chosen to optimize the structure and seismic activity for research; i.e. they will have a high probability of generating small to moderate earthquakes during the life of the project; (2) A dense array of instruments will be deployed to monitor the three-dimensional, nearfield processes of the earthquakes. The instruments will include seismometers, strainmeters, temperature sensors, displacement-meters, and devices to monitor strong-ground motion, electromagnetic radiation, acoustic emission, and time-variations of microbial communities and fault fluid and gas chemistry; and (3) The physical and chemical conditions of the active faults will be characterized by in-situ stress measurements and 3D mapping, and by extensive chemical and rock mechanics