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dc.contributor.authorHuffman, K.A.
Saffer, D.M.
Dugan, B.
dc.date.accessioned 2017-03-07T18:24:16Z
dc.date.available 2017-03-07T18:24:16Z
dc.date.issued 2016
dc.identifier.citation Huffman, K.A., Saffer, D.M. and Dugan, B.. "In situ stress magnitude and rock strength in the Nankai accretionary complex: a novel approach using paired constraints from downhole data in two wells." Earth, Planets and Space, 68, (2016) Springer Open: http://dx.doi.org/10.1186/s40623-016-0491-4.
dc.identifier.urihttps://hdl.handle.net/1911/94024
dc.description.abstract We present a method to simultaneously constrain both far-field horizontal stress magnitudes (S hmin and S Hmax) and in situ rock unconfined compressive strength (UCS), using geophysical logging data from two boreholes located 70 m apart that access the uppermost accretionary prism of the Nankai subduction zone . The boreholes sample the same sediments and are affected by the same tectonic stress field, but were drilled with different annular pressures, thus providing a unique opportunity to refine estimates of both in situ stress magnitudes and rock strength. We develop a forward model to predict the angular width of compressional wellbore failures (borehole breakouts), and identify combinations of S Hmax and UCS that best match breakout widths observed in resistivity images from the two boreholes. The method requires knowledge of S hmin, which is defined by leak-off tests conducted during drilling. Our results define a normal to strike-slip stress regime from 900 to 1386 m below seafloor, consistent with observations from seismic and core data. Our analysis also suggests that in situ values of UCS are generally slightly lower that commonly assumed on the basis of published empirical relations between UCS and P-wave velocity.
dc.language.iso eng
dc.publisher Springer Open
dc.rightsThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.title In situ stress magnitude and rock strength in the Nankai accretionary complex: a novel approach using paired constraints from downhole data in two wells
dc.type Journal article
dc.citation.journalTitle Earth, Planets and Space
dc.subject.keywordNankai Trough
In situ stress
Unconfined compressive strength
Borehole breakout
IODP
dc.citation.volumeNumber 68
dc.type.dcmi Text
dc.identifier.doihttp://dx.doi.org/10.1186/s40623-016-0491-4
dc.type.publication publisher version
dc.citation.articleNumber 123


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