Development of Characterization Technology for Fault Zone Hydrology Page: 2 of 8
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develop a methodology for characterizing the hydrology of
fault zones, recognizing that the efficient and reliable
characterization of faults is crucial to the safe geologic isolation
of nuclear wastes.
Given the geologic environment of the Japanese
Islands-they are likely to exist almost everywhere-faults
need to be assessed both at the preliminary and the detailed
investigation stage (the length scale of the faults of interest
could range from several kilometers in the former down to
several hundred meters in the latter).
Efforts in the past, though, have rarely addressed the
development of a systematized hydrologic characterization
technology specifically tailored for fault zones. Instead, it has
been necessary to use overly conservative values for the
hydrologic parameters of fault zones in the design and
performance assessment of a repository. Thus, development of
a more efficient and reliable fault-zone characterization
technology is acutely needed. The geologic properties of faults
and the relationships among their geometry, type, fault
parameters, and internal structures have been investigated in the
past. However, the relationship between the geologic and
hydrologic properties of faults is not yet studied sufficiently.
Karasaki et al. [1] concluded that there is very little available in
the literature that relates the geologic structure of faults to
hydrology, that it still may be feasible to classify faults based
on geologic attributes to predict their hydrologic characteristics,
and that it is critical to establish a field investigation technology
for fault zone hydrology.
The Wildcat Fault (Figure 1), which is a predominantly
strike-slip fault and a member of the Hayward Fault system,
was chosen to be the target fault of the field study. Wildcat runs
through the LBNL property, within and around which surface-
based investigations have been conducted. A total of five
trenches have been excavated. Surface geophysical
investigations were conducted using electrical resistivity survey
and seismic reflection profiling along four lines on the north, inthe middle and to the south of the LBNL site. In addition, three
150 m deep boreholes were drilled.
The present paper presents an overview of this ongoing
project, the results of which have so far been intriguing, and in
some ways contradictory to past, published work regarding this
site.
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Figure 2 Geologic map of the area around the LBNL site, modified
after Graymer[6]. The location of LBNL and the area shown in
Figure 3 are indicated by broken and solid white lines, respectively.Table 1 Regional Stratigraphy of San Francisco Bay Area (Compiled from [2], [3] and [6])
Era Period Epoch Group Formation Lithology Deposition/Deformation
Pleistocene/ Colluvium/ Clays and silts and weathered Resulted from erosional process
Quaternary HooeeLandslide materialReutdfoersnapocs
deposits
Late Miocene Contra Costa Volcanic flows of basalt and Lava flow related to eruption of Bald Peak
Pliocene Moraga andesite; tuff and Round Top volcanoes
5 Poorly consolidated sandsone, Flood plan or alluvial to shallow lake
Miocene- Contra Costa Orinda siltsone, claystone, occasional depositional environment. Unconformity
Pliocene cnlm
heneconglomerate glomover Claremont Fm.
N eogene M -o ene San- - - --a- - - - --r- - - - - - - - - - - - - - - - - - - -
Pliocene San Pablo Briones (?) sandstone shallow marine environment
Middle Siliceous shale, chert, siltstone, Marine deposition;
ne Monterey Claremont wcaiona sanishe s e nterbedded, folded, fractured and
faulted and overturned beds.
Coast Range CRO= rocks of upper mantle
Great Valley Ophiolite (CRO) (serpentine) to basalt Fore-arc basin sediments over 10 km thick
u GVS= marine sedimentary rocks
Cretaceous to Complex and Great Valley over oceanic rocks.
Juasi Sequence (snstnGhleVonlmeae
Jurassic volcanic eroded material)
Pillow basaslts, cherts, m6langes From ocean spread center to subduction and
Franciscan of greywacke and shale accretion process.
Sheared and faulted.
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Karasaki, Kenzi; Onishi, Tiemi; Gasperikova, Erika; Goto, Junichi; Tsuchi, Hiroyuki; Miwa, Tadashi et al. Development of Characterization Technology for Fault Zone Hydrology, article, August 6, 2010; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc1014656/m1/2/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.