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Geodesy's contribution to geophysics
OLR (1984) 31 (12)
D. Submarine Geology and Geophysics
84:6123 Rummel, Reiner, 1984. Geodesy's contribution to geophysics. Interdiscipl. Sci. Rev., 9(2): 113-122. Formally, geodesy is the science of the measurement, determination, and mapping of the shape of the Earth's surface and its variations with time. Because of recent technological advances, it 'approaches a 10 8 relative precision in its efforts to determine the shape of the Earth and of its gravity field.' Contributions of geodesy to the earth sciences include direct measurement of tectonic motion, resolution of the fine structure of the gravity field, and measurement of the orientation of the Earth in space. Dept. of Geodesy, Delft Univ. of Tech., Delft, Netherlands. (amt) 84:6124 Takahashi, Shinji, 1983. Magnetic properties of submarine basalts from Site 443 of DSDP Leg 58, the Shikokn Basin. J. Geomagn. Geoelect., 35(8):281-303. Thermomagnetic properties, lattice constants and optical properties of Fe-Ti oxide minerals in 31 samples indicate that the magnetic properties are not dependent on depth from sub-bottom but on their lithological facies. The magnetic minerals were classified in four types (reversible, semi-irreversible, irreversible, high Curie temperature). Irreversible specimens seem to be reconstituted by a certain heat treatment, suggesting that the mechanism of thermo-chemical change in low temperature-oxidized (non-stoichiometric) minerals be reconsidered. Dept. of Earth Sci., Kobe Univ., Kobe, Japan. 84:6125 Wu, Mingxian, 1984. Modelling calculation of sea-
mount [magneticl anomalies. Oceanologia Limnol. sin., 15(1):21-26. (In Chinese, English abstract.) Shandong College of Oceanol., People's Republic of China.
D240. Local or regional tectonics 84:6126
Chandra, Umesh, 1984. Tectonic segmentation of the Burmese-Indonesian Arc. Tectonophysics, 105(1/4):279-289. Two transverse boundary zones (North Andaman and Sunda) that separate segments of the arc are identified. The larger than usual thickness of the oceanic crust beneath the Ninetyeast Ridge reduces the average density of the lithosphere carrying the ridge. The buoyancy effect inhibits subduction of an
875
approximately triangular shaped lithosphere between the Burmese-Indonesian Arc and the Ninetyeast Ridge, which in turn causes tectonic segmentation along the arc. The model predicts and some available focal mechanism solutions confirm left lateral NE faulting within the Sunda Boundary Zone. Ebasco Services, Inc., 2211 W. Meadowview Rd., Greensboro, NC 27407, USA. 84:6127 Eissler, H.K. and K.C. McNally, 1984. Seismicity and tectonics of the Rivera Plate and implications for the 1932 Jalisco, Mexico, earthquake. J. geophys. Res., 89(B6):4520-4530. The proposed Rivera-Cocos plate boundary was examined as to historic seismicity and by relocating earthquakes along the Rivera Fracture Zone and Mid-America Trench using the joint epicenter determination method with the object of determining whether an apparent seismic gap in Jalisco, Mexico, reflects a true deficiency of activity or slower subduction of the Rivera Plate compared to the Cocos Plate. The relocated seismicity suggests Rivera-Cocos relative motion but does not resolve whether the Jalisco region should be considered a seismic gap for which rupture may be imminent. Seismological Lab., Calif. Inst. of Tech., Pasadena, Calif., USA. (amt) 84:6128 Engeln, J.F. and Seth Stein, 1984. Tectonics of the Easter Plate. Earth planet. Sci. Lefts, 68(2):259270. A model for the Easter Plate in which rift propagation results in the formation of a rigid plate between the propagating and dying ridges is presented. Both the Easter-Nazca and Easter-Pacific Euler poles are sufficiently close to the Easter Plate to cause rapid changes in rates and directions of motion along the boundaries. The east and west boundaries are propagating and dying ridges; the southwest boundary is a slow-spreading ridge and the northern boundary is a complex zone of convergent and transform motion. The Easter Plate may reflect the tectonics of rift propagation on a large scale where rigid plate tectonics requires boundary reorientation. Simple schematic models illustrate the general features and processes which occur at plates resulting from large-scale rift propagation. Dept. of Geol. Sci., Northwestern Univ., Evanston, Ill. 60201, USA. 84:6129
Finetti, Icilio, 1984. Structure and evolution of the Adriatic micropinte. Boll. Oceanol. teor. appl., II(2):115-124. (In Italian, English abstract.)
D. Submarine Geology and Geophysics
84:6123 Rummel, Reiner, 1984. Geodesy's contribution to geophysics. Interdiscipl. Sci. Rev., 9(2): 113-122. Formally, geodesy is the science of the measurement, determination, and mapping of the shape of the Earth's surface and its variations with time. Because of recent technological advances, it 'approaches a 10 8 relative precision in its efforts to determine the shape of the Earth and of its gravity field.' Contributions of geodesy to the earth sciences include direct measurement of tectonic motion, resolution of the fine structure of the gravity field, and measurement of the orientation of the Earth in space. Dept. of Geodesy, Delft Univ. of Tech., Delft, Netherlands. (amt) 84:6124 Takahashi, Shinji, 1983. Magnetic properties of submarine basalts from Site 443 of DSDP Leg 58, the Shikokn Basin. J. Geomagn. Geoelect., 35(8):281-303. Thermomagnetic properties, lattice constants and optical properties of Fe-Ti oxide minerals in 31 samples indicate that the magnetic properties are not dependent on depth from sub-bottom but on their lithological facies. The magnetic minerals were classified in four types (reversible, semi-irreversible, irreversible, high Curie temperature). Irreversible specimens seem to be reconstituted by a certain heat treatment, suggesting that the mechanism of thermo-chemical change in low temperature-oxidized (non-stoichiometric) minerals be reconsidered. Dept. of Earth Sci., Kobe Univ., Kobe, Japan. 84:6125 Wu, Mingxian, 1984. Modelling calculation of sea-
mount [magneticl anomalies. Oceanologia Limnol. sin., 15(1):21-26. (In Chinese, English abstract.) Shandong College of Oceanol., People's Republic of China.
D240. Local or regional tectonics 84:6126
Chandra, Umesh, 1984. Tectonic segmentation of the Burmese-Indonesian Arc. Tectonophysics, 105(1/4):279-289. Two transverse boundary zones (North Andaman and Sunda) that separate segments of the arc are identified. The larger than usual thickness of the oceanic crust beneath the Ninetyeast Ridge reduces the average density of the lithosphere carrying the ridge. The buoyancy effect inhibits subduction of an
875
approximately triangular shaped lithosphere between the Burmese-Indonesian Arc and the Ninetyeast Ridge, which in turn causes tectonic segmentation along the arc. The model predicts and some available focal mechanism solutions confirm left lateral NE faulting within the Sunda Boundary Zone. Ebasco Services, Inc., 2211 W. Meadowview Rd., Greensboro, NC 27407, USA. 84:6127 Eissler, H.K. and K.C. McNally, 1984. Seismicity and tectonics of the Rivera Plate and implications for the 1932 Jalisco, Mexico, earthquake. J. geophys. Res., 89(B6):4520-4530. The proposed Rivera-Cocos plate boundary was examined as to historic seismicity and by relocating earthquakes along the Rivera Fracture Zone and Mid-America Trench using the joint epicenter determination method with the object of determining whether an apparent seismic gap in Jalisco, Mexico, reflects a true deficiency of activity or slower subduction of the Rivera Plate compared to the Cocos Plate. The relocated seismicity suggests Rivera-Cocos relative motion but does not resolve whether the Jalisco region should be considered a seismic gap for which rupture may be imminent. Seismological Lab., Calif. Inst. of Tech., Pasadena, Calif., USA. (amt) 84:6128 Engeln, J.F. and Seth Stein, 1984. Tectonics of the Easter Plate. Earth planet. Sci. Lefts, 68(2):259270. A model for the Easter Plate in which rift propagation results in the formation of a rigid plate between the propagating and dying ridges is presented. Both the Easter-Nazca and Easter-Pacific Euler poles are sufficiently close to the Easter Plate to cause rapid changes in rates and directions of motion along the boundaries. The east and west boundaries are propagating and dying ridges; the southwest boundary is a slow-spreading ridge and the northern boundary is a complex zone of convergent and transform motion. The Easter Plate may reflect the tectonics of rift propagation on a large scale where rigid plate tectonics requires boundary reorientation. Simple schematic models illustrate the general features and processes which occur at plates resulting from large-scale rift propagation. Dept. of Geol. Sci., Northwestern Univ., Evanston, Ill. 60201, USA. 84:6129
Finetti, Icilio, 1984. Structure and evolution of the Adriatic micropinte. Boll. Oceanol. teor. appl., II(2):115-124. (In Italian, English abstract.)