Preliminary results on horizontal stress orientation and stress magnitude off Osa Peninsula, Costa Rica

Author(s): Saito, S.; Malinverno, Alberto; Lin, W.; Yamamoto, Y.; Wu, H.; Harris, R. N.; Sakaguchi, A.; Ujiie, K.; Vannucchi, Paola; Petronotis, K. E.
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
Lamont-Doherty Earth Boservatory, United States
Oregon State University, United States
Yamaguchi University, Japan
University of Tsukuba, Japan
University of London, Royal Holloway, United Kingdom
Texas A&M University, IODP, United States
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: During IODP Expeditions 334/344 borehole breakouts were successfully imaged by logging-while-drilling and wireline logging. The maximum horizontal principal stress (SHmax) orientation estimated from the breakouts is directed WSW-ENE at shelf sites (Sites U1379 and U1413, about 25 km landward of the deformation front) and NNE-SSW at a mid slope site (Sites U1378, about 15 km landward of the deformation front). These directions are approximately parallel and perpendicular to NNE-directed GPS deformation vectors on the Caribbean plate. The SHmax orientation combined with core analysis suggest that normal fault regime in the shelf sediments and strike-slip regime at shelf basement and mid-slope. The breakouts also yield useful information on stress magnitudes. The principle is that the width of the breakout is dependent on the stress magnitudes and the compressive strength of the borehole wall rock. In order to constrain the range of possible stress magnitudes, we conducted uniaxial compressional strength (UCS) tests. Most of the preliminary UCS results range from 1 to 3 MPa. The UCS values combined with the width of borehole breakouts suggest that the stress regime is in the normal faulting stress regime in the shelf sites.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Cores; Costa Rica Seismogenesis Project; East Pacific; Expedition 334; Expedition 344; IODP Site U1378; IODP Site U1379; IODP Site U1413; Integrated Ocean Drilling Program; Marine sediments; North Pacific; Northeast Pacific; Osa Peninsula; Pacific Ocean; Sediments
Coordinates: N084427 N084428 W0840648 W0840649
N084051 N084051 W0840201 W0840202
Record ID: 2015031174
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