Seaward slope faults in the Pacific plate along the Aleutian Trench /
Side-scan sonar images of the seaward trench slope along the
| Main Author: | |
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=743273591&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Side-scan sonar images of the seaward trench slope along the Aleutian Trench provide constraints in the stress-field in the uppermost part of the oceanic lithosphere. The relationships between faults and shallow earthquakes are examined to define the stress-field along a convergent- transform plate boundary. GLORIA images show two trends of fault patterns in the Aleutian seaward trench slope (165'E-165'W). Between Amlia F.Z. (AFZ) and Rat F.Z. (RFZ), most faults strike nearly parallel to the trench; whereas west of RFZ and east of A- FZ, faults strike oblique to the trench (13-26'). West of AFZ, earthquake nodal-planes of normal faults in the seaward trench slope have strikes nearly parallel to the trends of seaward slope faults; while east of AFZ, the nodal-planes are not concordant with the fault-trends. Most epicenters in the oceanic lithosphere are confined no farther than 2/3 of the trench-outer rise distance. Gravity data show that the outer-rise extends from Alaska Peninsula to Stalemate Ridge. West of RFZ, faults intersect the magnetic lineations at 52-74'; whereas east of RFZ, faults strike nearly parallel to the magnetic lineations. Different orientations of fault-trends and nodalplanes indicate three strain-stress regions to the south of the trench. Western-region (1 69'E- 179'E), trench-oblique faults are 37' from the fault-trends to the east of 179'E. This change occurs where the trench- parallel slip component of convergence is larger than the trench-perpendicular component, implying that the lateral dextral shearcouple along this boundary redirects the stress in the oceanic lithosphere. Fault-trends and nodal- plane orientations are best explained by a stress-field near the trench that results from superimposing shear- stresses on bending-stresses. Central-region (I 790E- 173OW), fault-trends and nodal-planes are parallel to the trench and magnetic lineations. It is difficult to discern whether bending or the superimposed stresses control the fault-trends in this region. Eastern-region (173'W-165'W), nodal-planes are aligned with the bending axis in the upper-part of the lithosphere; while faults are oriented parallel to pre-existing faults associated with seafloor spreading. Fault-trends are discordant with the nodal- planes by 9-47'. This suggests that fresh-faults associated with earthquakes at 10-40 km depths result from pure bending; while pre-existing faults at depths <10 km are reactivated by bending. |
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| Item Description: | Vita. "Major Subject: Geophysics". |
| Physical Description: | xii, 218 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |