Scientific Drilling of Active Faults: Past and Future

Reches, Z.; Ito, Hisao

doi:10.1007/978-3-540-68778-8_6

Cited by 9 publications

(6 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The present study is part of the Natural Earthquake Laboratory in South African Mines (NELSAM) project, which was designed to investigate seismogenic processes at focal-depths in deep gold mines in South Africa (RECHES, 2006;RECHES and ITO, 2007). The mines provide a unique setting with in situ access to hypocenters of earthquakes of moment-magnitude -2 to *4, with the larger magnitudes often occurring along pre-existing fault-zones.…”

Section: Nelsam Projectmentioning

confidence: 99%

Earthquake Rupture at Focal Depth, Part I: Structure and Rupture of the Pretorius Fault, TauTona Mine, South Africa

Heesakkers

Murphy

Reches

2011

Pure Appl. Geophys.

View full text Add to dashboard Cite

We analyze the structure of the Archaean Pretorius fault in TauTona mine, South Africa, as well as the rupture-zone that recently reactivated it. The analysis is part of the Natural Earthquake Laboratory in South African Mines (NELSAM) project that utilizes the access to 3.6 km depth provided by the mining operations. The Pretorius fault is a *10 km long, oblique-strikeslip fault with displacement of up to 200 m that crosscuts fine to very coarse grain quartzitic rocks in TauTona mine. We identify here three structural zones within the fault-zone: (1) an outer damage zone, *100 m wide, of brittle deformation manifested by multiple, widely spaced fractures and faults with slip up to 3 m; (2) an inner damage zone, 25-30 m wide, with high density of anastomosing conjugate sets of fault segments and fractures, many of which carry cataclasite zones; and (3) a dominant segment, with a cataclasite zone up to 50 cm thick that accommodated most of the Archaean slip of the Pretorius fault, and is regarded as the 'principal slip zone' (PSZ). This fault-zone structure indicates that during its Archaean activity, the Pretorius fault entered the mature fault stage in which many slip events were localized along a single, PSZ. The mining operations continuously induce earthquakes, including the 2004, M2.2 event that rejuvenated the Pretorius fault in the NELSAM project area. Our analysis of the M2.2 rupture-zone shows that (1) slip occurred exclusively along four, pre-existing large, quasi-planer segments of the ancient fault-zone; (2) the slipping segments contain brittle cataclasite zones up to 0.5 m thick; (3) these segments are not parallel to each other; (4) gouge zones, 1-5 mm thick, composed of white 'rock-flour' formed almost exclusively along the cataclasite-host rock contacts of the slipping segments; (5) locally, new, fresh fractures branched from the slipping segments and propagated in mixed shear-tensile mode; (6) the maximum observed shear displacement is 25 mm in oblique-normal slip. The mechanical analysis of this rupture-zone is presented in Part II (HEESAKKERS et al.,

show abstract

Section: Nelsam Projectmentioning

confidence: 99%

Earthquake Rupture at Focal Depth, Part I: Structure and Rupture of the Pretorius Fault, TauTona Mine, South Africa

Heesakkers

Murphy

Reches

2011

Pure Appl. Geophys.

View full text Add to dashboard Cite

show abstract

“…Two recently published reviews of fault zone drilling activity by Reches and Ito (2007) and Zoback et al (2007) both discuss the principal specific scientific goals of recent, active, and planned projects in detail, and it would be redundant to duplicate them here. Zoback et al (2007) summarized the fundamental motivation well, writing: "It is currently impossible to differentiate between-or even adequately constrain-the numerous conceptual models of active faults proposed over the years (Fig.…”

Section: Workhop Organizationmentioning

confidence: 99%

Joint IODP-ICDP Workshop Examines Challenges of Fault Zone Drilling

Tobin

Ito

Behrmann

et al. 2007

Scientific Drilling

Self Cite

View full text Add to dashboard Cite

“…Here, we briefly summarize some of the key scientific motivations for engaging in fault zone drilling that were especially highlighted at the workshop. Two recently published reviews of fault zone drilling activity by Reches and Ito (2007) and Zoback et al (2007) both discuss the principal specific scientific goals of recent, active, and planned projects in detail, and it would be redundant to duplicate them here. Zoback et al (2007) summarized the fundamental motivation well, writing: "It is currently impossible to differentiate between-or even adequately constrain-the numerous conceptual models of active faults proposed over the years (Fig.…”

Section: Workhop Organizationmentioning

confidence: 99%