HR: 13:40h
AN: T43D-01 INVITED     [Abstracts]
TI: Drilling Across Active Faults in Deep Mines in South Africa for Monitoring Earthquake Processes in the Near-Field
AU: * Reches, Z
EM: reches@ou.edu
AF: School of Geology and Geophysics, University of Oklahoma, 100 E Boyd St., Norman, OK 73019
AU: Jordan, T H
EM: tjordan@earth.usc.edu
AF: Southern California Earthquake Center, University of Southern California, Los Angeles, CA 90089
AU: Johnston, M J
EM: mal@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025
AU: Zoback, M
EM: zoback@pangea.stanford.edu
AF: School of Earth Sciences, Stanford University, Stanford, CA 94305
AB: Deep mines can provide three-dimensional access to fault-zones that are likely to be activated by the mining operations. To take advantage of this option, we ranked 12 active faults in South African mines according to dimensions, internal structure, accessibility, and likelihood of M>3.0 seismic events. The selected site is on the Pretorius fault, which is 10 km long with throw of 30-60 m, and which is exposed at multiple levels in TauTona and Mponeng gold mines, Western Deep Levels. The DAFSAM-NELSAM project (earthquakes.ou.edu) focuses on establishing a natural earthquake laboratory along the Pretorius fault at 3.5 km depth in TauTona mine. The work on the site started in January, 2005, and has been devoted so far to site characterization, including 3D mapping and in-situ stress measurements, and drilling short holes for accelerometers-seismometers. Cross-fault drilling will initiate in September, 2005, and will include four boreholes 40-60 m long each for the installation of creepmeters strain meters, temperature sensors, acoustic emission transducers, and gas analyzers. The monitoring site is established where both sides of the Pretorius fault and the practice in the deep mines and numerical modeling predict profound increase of the seismic activity at the site during the next 2-4 years. The associated increase of shear stresses on the fault is expected to generate a few earthquakes of M>3.0 along the segments of the Pretorius fault. We will present the feature of the monitoring system, and the main current results of fault characteristics and state of stress.
UR: http://earthquakes.ou.edu/
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8010 Fractures and faults
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8150 Plate boundary: general (3040)
SC: Tectonophysics [T]
MN: Fall Meeting 2005