Integrated geophysical investigations were conducted around Awash Melkesa, located 106 km southeast of Addis Ababa, utilizing electrical resistivity, magnetic, radiometric, and seismic refraction methods. The geo-electric profile revealed five layers, with a notable low resistivity zone (113 Ohm-m) beneath VES 2, indicating a highly fractured and weathered ignimbrite, which suggests good potential for aquifers. The residual magnetic anomaly map varied from -312-296 nT, pointing to alluvial and pyroclastic sediments, while the tilt derivative magnetic map identified several faults oriented in N-S and NE-SW directions, consistent with the Wonji fault belt. Additionally, high concentrations of uranium and thorium were found in areas with felsic and intermediate extrusive igneous rocks, whereas lower concentrations were associated with weathered felsic rocks. The seismic velocity model identified three layers: the top layer, 3 m thick, showed P-wave velocities of 0.3-0.7 km/s; the second layer, at depths of 3-9 m, had velocities of 0.75-1.2 km/s, likely representing unconsolidated pyroclastic ignimbrite; and the third layer, between 9-18 m, exhibited a P-wave velocity of 2 km/s, indicating somewhat weathered and fractured ignimbrite. These findings provide valuable insights into the subsurface geophysical characteristics and potential resources in the Awash Melkesa area.
Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600310325-6 CENTRAL INTEITMEMIRPI INFORMATION' FROM FOREIGN DOCUMENTS OR RADIO BROADCASTS COUNTRY USSR SUBJECT Scientific - Geophysical prospecting HOW PUBLISHED Periodicals WHERE PUBLISHED USSR DATER PUBLISHED 1949 LANGUAGE THIS DOCUMENT CONTAINS INFORMATION AFFECTING THE NATIONAL DEFENSE OP THE UNITED STATES WITHIN THE MEANING OF ESPIONAGE ACT BO U. S. C.. St AND 32. AS AMENDED. ITS TRANSMISSION OR THE REVELATION OF ITS CONTENTS IN AMT MANNER TO AN UNAUTHORIZED PERSON IS PRO- NIBITED By LAW. REPRODUCTION OF THIS FORM IS PROHIBITE O. REPORT CD NO. DATE OF DATE DIST. t4 May 1950 NO. OF PAGES 9 SUPPLEMENT TO REPORT NO. THIS IS UNEVALUATED INFORMATION REVIEW OF 1949 SOVIET PERIODICAL LITERATURE ON GEOPHYSICAL PROSPECTING umbers in parentheses refer to the appended bibliographr_7 Soviet research in geophysical prospecting includes electrical, seismic, gravitational, and thermal methods with emphasis on the first two, according to articles published in Soviet periodical literature. Electrical Methods According to a report by Enenshteyn and Aronoir (1), a field method for studying electric fields in the earth wab worked out in theory by A. N. Tikhonov in the Geophysics Institute, Academy of Sciences USSR. This method, according to the authors, demanded new instruments as well as new techniques in field study. The method developed is described as follows: A transmit- ting dipole consisting of the usual electrical pr
Rifting of continental crust is likely to be influenced by pre-existing intra-basement structures inherited from previous tectonic events. However, the origin, nature, 3D geometry and the mechanisms controlling the reactivation of these pre-existing structures during later phases of rifting are not well understood. This is mainly due to limitations in borehole penetration, seismic imaging and complex overprinting of multiple phases of deformation. This study investigates how structures related to the Caledonian orogeny and subsequent Devonian extensional tectonics influence the structural evolution and geometry of the North Sea rift basin. In a first step, the lithological composition and three-dimensional structural architecture of crystalline basement is established using borehole, 3D seismic reflection and potential field data, as well as correlations with the Norwegian onshore geology. In addition, synthetic seismogram modelling and 2D forward modelling of gravity and magnetic data are used to constrain the seismic interpretation of the subsurface. Having determined the structural configuration of crystalline basement, this study then investigates the 3D-geometrical and kinematic relationships between intra-basement structures and rift-related normal faults and discusses the relative influence of inherited structures on rift geometry at the local and regional scale. Results show that crystalline basement is highly heterogeneous, comprising various igneous and metamorphic
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