Showing papers in "Developments in Solid Earth Geophysics in 1983"
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TL;DR: In this paper, additional field work in Finnish Lapland in connection with the Fennoscandian Long-Range Project is reported and some record sections made by computer for the profiles are presented.
Abstract: The additional field work in Finnish Lapland in connection with the Fennoscandian Long-Range Project is reported and some record sections made by computer for the profiles are presented. According to a preliminary model derived the average velocity in the crust is about 6.6 km/s, in the uppermost mantle about 8.4 km/s, and the thickness of the crust is 49 km.
16 citations
TL;DR: Crustal investigations of Western Portugal, along the Mesozoic zone situated between Lisboa and Nazare, show the following major characteristics: in the uppermost 8 km the velocity increases continuously with increasing depth reaching the unusually high value of 6.5 km/s; this layer is underlain by a sialic low-velocity layer, probably constituted by granite of the primordial Iberian Tableland; the lower crust shows the normal pattern as found in many other profiles of Hercynian Europe.
Abstract: Crustal investigations of Western Portugal, along the Mesozoic zone situated between Lisboa and Nazare, show the following major characteristics: in the uppermost 8 km the velocity increases continuously with increasing depth reaching the unusually high value of 6.5 km/s; this layer is underlain by a sialic low-velocity layer, probably constituted by granite of the primordial Iberian Tableland; the lower crust shows the normal pattern as found in many other profiles of Hercynian Europe. The crust-mantle boundary is a 3 — 5 km wide transition zone with P-wave velocity of 8.2 km/s at 31 km depth. This confirms the existence of continental crust along the Mesozoic zone of Western Portugal with the characteristics of the so-called normal European crust.
16 citations
TL;DR: The Sierentz earthquake on July 15, 1980 occurred in the southern part of the Rhinegraben, about 20 km NNW from BASEL as discussed by the authors and was preceded, 0.6 second before, by a magnitude 2 foreshock.
Abstract: The Sierentz earthquake on July 15, 1980 occurred in the southern part of the Rhinegraben, about 20 km NNW from BASEL. The main shock (ML = 4.8) was preceded, 0.6 second before, by a magnitude 2 foreshock. A portable station network (15 stations) has been established in the epicentral area within 10 hours after the main shock occurred. 400 events with magnitude ranging from 0.0 to 4.0 have been recorded during the following sixteen days. The sequence exhibits a low b-value (-0.54). Fault plane solutions of the foreshock, the main shock and the three largest aftershocks are presented and discussed.
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TL;DR: In this article, a non-geometrical arrival, denoted as S*, has been detected in synthetic seismograms representing an exact solution to Lamb's problem for an explosive point source located close to the free surface.
Abstract: A new and very prominent non-geometrical arrival, denoted as S*, has been detected in synthetic seismograms representing an exact solution to Lamb's problem for an explosive point source located close to the free surface. The new arrival displays a linear polarization and propagates with the speed of an ordinary shear wave. Seemingly, it originates on the free surface directly above the buried P source with an amplitude which decays exponentially with source depth. Under favorable circumstances, i.e. when the source depth is less than the predominant wavelength of the source pulse, the S* arrival may be stronger than any other body wave arriving at a given epicentral distance. The full understanding of its properties and nature will have a direct impact on the interpretation of field seismograms in oil exploration where, as a rule, explosive sources are always close to the surface.
TL;DR: In this article, the authors distinguish two deep fault zones of the crust: the Ionian-Adriatic fault zone and the zone of Shkodra depressional faults.
Abstract: On the basis of the seismotectonic analysis we distinguish two deep fault zones of the crust: The Ionian-Adriatic fault zone and the zone of Shkodra depressional faults. The earthquake of April 15, 1979 was generated from the first deep fault zone of the crust that is located on the outer side of the orogene, of the Dinaride-Albanide-Hellenide branch of the folded alpine belt of the Mediterranean, at the border with the platform. The seismogene block activated during the earthquake was the under water Ulqin-Budva block with a length of 40 km.
TL;DR: The focal mechanism solution of the April 15, 1979 earthquake demonstrates that compressional forces are responsible for the seismic activity along the Adriatic coast as mentioned in this paper, which corresponds to an almost vertical reverse faulting with dipslip motion, in which the western block overrides the eastern one.
Abstract: The focal mechanism solution of the April 15, 1979 earthquake demonstrates that compressional forces are responsible for the seismic activity along the Adriatic coast. The nodal plane, identified with the plane of faulting strikes in the direction N 46°W and has a large dip. The mechanism corresponds to an almost vertical reverse faulting with dipslip motion, in which the western block overrides the eastern one. The focal mechanism solution has shown that this earthquake sequence was the result of the reactivation of the deep-faulted Ionian-Adriatic zone between the orogene and the stable foreland.
TL;DR: A multidisciplinary approach to earthquake prediction in the North Anatolian Fault Zone was proposed by Friedr et al. as discussed by the authors at an international conference held in Istanbul, where experts from many countries in the fields of geophysics, geology and geodesy met.
Abstract: Studies of the sources of earthquakes, the only way towards successful prediction requires a broad interdisciplinary approach and a cooperation between scientists in various fields of earth sciences, Studies of seismotectonics, strain changes and physical state and properties in the earthquake source region are the main lines to be followed. The North Anatolian Fault Zone is an area of extremely high earthquake risk. At an international conference held in Istanbul experts from many countries in the fields of geophysics, geology and geodesy met to report on the results of earlier research and present activities relevant to earthquake prediction in the North Anatolian Fault Zone and to define and organize a program for earthquake prediction research in the most riskful part of this area. Proceedings of the conference on a multidisciplinary approach to earthquake prediction in the North Anatolian Fault Zone will be published by Friedr. Vieweg, Wiesbaden-Braunschweig (Isikara et al., Editors, 1931)