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The full range of 50 initial, Moon-orbit-forced superharmonic resonance periods is detected in the 1969-1977 time-series of all 12474 consecutive 0.02 Hz moonquakes from the Apollo Program catalog. The resonance is found forcing the strongest-energy (highest-fidelity) part of the 10 hours–100 days (27.78–0.115741 μHz) long-periodic band at 99–67% confidence and below. Resonance signatures of the Moon’s other four long tidal periods – synodic, anomalistic, nodical, and tropical – were also identified but not as separate drivers of body resonance. The spectra were computed using a least-squares spectral analysis method that enabled separation of the signal driver and noise signatures of all lunar tides, as well as extraction of the exact sequence of resonance periods affecting the solid Moon. As the main disruptive phase, the Moon’s orbital period introduces nonlinearity into lunar vibration and thus forces lunar seismotectonics too, giving rise to superharmonic resonance and probably the so-called free librations as well. The spatiotemporally independent computations of Earth and Moon superharmonic resonances from seismicity time-series prove that (the magnification of) macroscopic mechanical resonance is from-quantum-to-macroscopic-scales universal, and therefore as important as gravitation and fundamental forces. I propose then that some of the craters and calderas in our Solar system are petrified evidence of polygonal Faraday latticing. Finally, since only planets with one moon are susceptible to resonance plate tectonics, to prevent Earth energy overload and disintegration, a global geoengineering scheme is proposed to reassign the smaller of Martian moons, Deimos, to Earth so to attenuate Earth plate tectonics while unlocking Mars plate tectonics for natural terraforming.
ARK: https://n2t.net/ark:/88439/x034508
Permalink: https://geophysicsjournal.com/article/73
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DOI:10.5281/3376564 | online first: 24 Aug 2019 CERN
Earth body resonance, 63(1):15-29
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As part of the RRISP 77 combined land-sea refraction seismic experiment, observations were carried out on Iceland itself with special emphasis on resolving the deep structure beneath Iceland and its transition towards the eastern flank of Reykjanes Ridge. The data, interpretational procedures, and results for the land part are described in this paper. A structural model of Iceland is presented which is characterized by a generalized two-layered crust of variable thickness underlain by anomalous mantle with P-wave velocities of 7.0 km/s at the base of the crust increasing to 7.4 km/s at 30 km depth. Two regions of relatively low velocity have been identified in the lower crust, possibly indicating zones of high melt concentration. A normal P- to S-wave velocity ratio of 1.76 is found within the crust, whereas this ratio reaches unusually high values of up to 2.2 in the anomalous mantle. From this and the P-wave velocity distribution the amount of partial melt is calculated. The melt content is highest (17%-23%) at the top of the mantle and decreases with increasing depth indicating differentiation processes in the upper mantle. The anomalous mantle is confined to Iceland and a sharp transition exists in the area of the shelf edge where normal oceanic lithosphere replaces the updoming asthenosphere.
ARK: https://n2t.net/ark:/88439/y083228
Permalink: https://geophysicsjournal.com/article/72
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A joint interpretation of all seismic-refraction profiles in the southern part of the Rhinegraben area is presented. A time-term analysis of all Pg-arrivals reveals the topography of the crystalline basement and provides an average velocity of 6.0 km/s for the uppermost crust. The crust-mantle boundary is clearly elevated in the Rhinegraben rift system forming an arch with a span of 150-180 km and reaching a depth of only 25 km at the flanks of the graben proper. The velocity of P-waves in the uppermost mantle is 8.0-8.1 km/s. Below the flanks of the graben, the crust-mantle boundary is formed by a first-order discontinuity. Within the graben proper it is replaced by a transition zone of 4 km thickness with the strongest velocity gradient at a depth of 21 km. This transition zone is regarded as region of crust-mantle interaction and seems to be confined to the graben proper.
ARK: https://n2t.net/ark:/88439/y074159
Permalink: https://geophysicsjournal.com/article/71
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By using data from the Technical University of Braunschweig flux-gate and search-coil magnetometer experiments on board of Helios 2 we study the spectral properties of the interplanetary magnetic field over a frequency range from 2.4 x 10-5 Hz up to 470 Hz. Examples of power spectral density estimates at different heliocentric distances are shown as well as the change of the spectra during the progress of a high speed stream. A general feature of the spectra is that in a log-log spectral representation the steepness of the power spectral density estimates varies as a function of frequency. If we relate the spectral densities by a power law P ∼ f –α, the spectral index α increases with increasing frequency. At 1 AU α varies on average from 1.6 to 3.4 and at 0.3 AU from 1.0 to 3.4, the major changes in the spectral index occurring at low frequencies. In addition, just within the frequency gap between the two experiments, between 2Hz and 4.7 Hz, an inflexion point is inferred from the spectrum above and below this frequency range. This spectral feature can at least partly be attributed to the damping of the Alfven-mode waves near the proton and also α-particle cyclotron frequencies. The observed power spectra are compared with models of MHD turbulence and it is found that at least some of the properties of MHD turbulence fit the observations remarkably well.
ARK: https://n2t.net/ark:/88439/y063880
Permalink: https://geophysicsjournal.com/article/70
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A steady-state plate-tectonic kinematic model of crustal accretion in Iceland is presented. It describes quantitatively the overall time-averaged movements of solid crustal elements during the accretion process, and correlates accretion parameters in the axial zone (width of lava deposition zone, total lava production rate, width of horizontal strain zone, spreading velocity, normal faulting) with structural properties in the Tertiary lava pile (lava dips, lava deposition rate, dyke fraction). The model is used, firstly, to predict the accretion parameters of the Tertiary volcanic zone on the basis of observed structural properties in the Tertiary lava pile; secondly, to predict possible structures of the lower crust in terms of a lava/intrusion ratio; thirdly, the model may be used to calculate the crustal temperature field caused by intrusions, but this application is outside the scope of the present paper. The model is essentially a further development of a previous one presented earlier by the author. The analysis, in terms of the model, of various published structural observations indicates that the width of lava deposition and the spreading rate in the Tertiary volcanic zone were consistent with the corresponding properties in the present-day volcanic zone. This may suggest a certain uniformity in the volcanic processes during the last 10-15 Ma. The visible Tertiary lava pile was, according to the model, deposited outside the innermost 50-km-wide central part of the volcanic zone, which may explain the difference in appearance between the two main volcanic regions of Iceland, i.e., the active volcanic zone and the Tertiary flood basalts. Furthermore, an analysis of possible structures of the lower crust, consistent with various surface observations, indicates a gradual rather than a sharp transition from an upper lava-dominated crust to a lower intrusion-dominated crust.
ARK: https://n2t.net/ark:/88439/y050901
Permalink: https://geophysicsjournal.com/article/69
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From the latest developments of algorithms for the computation of eigenvalues and eigenfunctions of Rayleigh waves for flat layered anelastic models of the Earth, it is possible to construct, with highly satisfactory efficiency and accuracy, "complete" synthetic seismograms also at high frequencies. Examples are given both for continental and oceanic structural models made up of 70 layers and more and extending to depths of about 1,100 km.
ARK: https://n2t.net/ark:/88439/y047312
Permalink: https://geophysicsjournal.com/article/67
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Differential Doppler measurements of signals from NNSS Navigational Satellites can be used to give the electron content of the ionosphere. Measurements carried out up to now using data from one station provide limited information about the structure of the ionosphere, since the method relies on an assumption being made about the prevailing ionospheric conditions. If these conditions are not fulfilled, this method can lead to large errors in the predicted electron content. In the method described in this paper, Differential Doppler data from two stations are combined, resulting in considerably more reliable results, particularly when there is strong horizontal structure in the ionosphere, as is often the case in Polar regions. Examples of model calculations and experimental measurements are also included.
ARK: https://n2t.net/ark:/88439/y034043
Permalink: https://geophysicsjournal.com/article/66
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The energy supplied to generate the Earth's magnetic field must ultimately result in heat flowing across the core-mantle boundary and through the Earth's surface. If the liquid core is stirred by thermal convection then only a small fraction of the total heat is dissipated in the electric currents, and in order to explain the observed field at least 1011 watt and probably 1013 watt of the Earth's surface heat flux must originate deep inside the core. If the core is cooling and there is concomitant chemical differentiation, a large amount of gravitational energy is released. This energy, unlike the heat released, is completely dissipated in the electric currents and enables the same magnetic field to be generated with a much lower heat flux. Chemical differentiation is therefore favoured as the energy source for the dynamo. The importance of gravitational settling depends on the density jump at the inner core boundary and on the stratification parameter in the outer core, both of which can, in principle, be determined seismologically.
ARK: https://n2t.net/ark:/88439/y027224
Permalink: https://geophysicsjournal.com/article/64
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A method for the interpretation of wide-angle reflection travel-times in laterally varying crust-mantle structures is formulated. A datum correction is first carried out by ray-tracing to remove the effects of refraction above the reflector. The resulting time-distance data may be then expressed in a form which permits, given multiple coverage of the sub-surface, the independent determination of velocity and reflector topography. The method has been tested on model data and found to be effective.
ARK: https://n2t.net/ark:/88439/y013185
Permalink: https://geophysicsjournal.com/article/58
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A simple model of mantle return flow in response to lithospheric plate motions is developed. Such a model is realistic if the buoyancy forces are concentrated in the plates. One-dimensionality is chosen as a simplification to study effects of mantle rheology in as much isolation as possible. Rheology is modelled as a combination of dislocation creep, diffusion creep and fluid phase transport; parameters are those appropriate for olivine. We have varied temperature, grain size, influence of partial melt, diffusivity and activation energy, grain deformation versus grain boundary sliding dominated creep, and surface plate velocity. A peculiar feature of non-linear rheology is the existence of low-stress high-viscosity regions, which, however, are of little dynamic importance because deformation there is very small. The main results are (1) that the model does not predict an excessive pressure gradient to be required by the return flow (which would be evident in a rise of the sea floor and strong increase in free air gravity anomalies toward the trenches); (2) that no excessive shear stresses at the plate bottom are predicted (which might result in observable heat flow effects and intra-plate seismicity and would require implausibly great driving forces at the plate ends); (3) that the model predicts the return flow to extend into the deeper mantle; this follows, however, from the simplifying assumption of olivine rheology below 400 km depth and would then argue for rather high temperatures, small grain sizes, possibly important fluid phase transport, and small activation volume. Recent work on the variation of activation volume with pressure and phase changes suggests a rather 'soft' lower mantle and thus supports the notion of 'deep' return flow. In interpreting the results one must, of course, keep in mind that the model is a purely mechanical one with a predetermined temperature profile (varied within plausible limits) and that the physics of the thermodynamic aspects of the flow problem is ignored.
ARK: https://n2t.net/ark:/88439/y009016
Permalink: https://geophysicsjournal.com/article/43
