排序方式： 共有27条查询结果，搜索用时 31 毫秒
1.
Stefani Marco Minarelli Luca Fontana Alessandro Hajdas Irka 《International Journal of Earth Sciences》2018,107(7):2433-2447
International Journal of Earth Sciences - Our research is aimed at estimating the vertical deformation affecting late Quaternary units accumulated into the foreland basin of the Northern Apennines... 相似文献
2.
3.
Jacopo Belfi Nicolò Beverini Giorgio Carelli Angela Di Virgilio Enrico Maccioni Gilberto Saccorotti Fabio Stefani Alexander Velikoseltsev 《Journal of Seismology》2012,16(4):767-776
We report the observation of the ground rotation induced by the M w = 9.0, 11th of March 2011, Japan earthquake. The rotation measurements have been conducted with a ring laser gyroscope operating in a vertical plane, thus detecting rotations around the horizontal axis. Comparison of ground rotations with vertical accelerations from a co-located force balance accelerometer shows excellent ring laser coupling at periods longer than 100?s. Under the plane wave assumption, we derive a theoretical relationship between horizontal rotation and vertical acceleration for Rayleigh waves. Due to the oblique mounting of the gyroscope with respect to the wave direction of arrival, apparent velocities derived from the acceleration/rotation rate ratio are expected to be always larger than or equal to the true wave propagation velocity. This hypothesis is confirmed through comparison with fundamental mode, Rayleigh-wave phase velocities predicted for a standard Earth model. 相似文献
4.
5.
F. Stefani G. Gerbeth Th. Gundrum J. Szklarski G. Rüdiger R. Hollerbach 《Astronomische Nachrichten》2008,329(7):652-658
The PROMISE experiment relies on the fact that the critical Reynolds number for the appearance of the magnetorotational instability (MRI) in liquid metal flows drastically decreases when the purely axial magnetic field is replaced by a helical one. We report the results of a modified version of this experiments in which the radial electrical boundary conditions are changed. Special focus is laid on the role of the radial jet region where the two Ekman vortices from the top and the bottom meet each other. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
7.
8.
Starting from the present version of the Riga dynamo experiment with its rotating magnetic eigenfield dominated by a single frequency we ask for those modifications of this set‐up that would allow for a non‐trivial magnetic field behaviour in the saturation regime. Assuming an increased ratio of azimuthal to axial flow velocity, we obtain energy oscillations with a frequency below the eigenfrequency of the magnetic field. These new oscillations are identified as magneto‐inertial waves that result from a slight imbalance of Lorentz and inertial forces. Increasing the azimuthal velocity further, or increasing the total magnetic Reynolds number, we find transitions to a chaotic behaviour of the dynamo (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
Polyphase Tectonics through subsidence analysis: the Oligo-Miocene Venetian and Friuli Basin, north-east Italy 总被引：1，自引：0，他引：1
Subsidence and provenance analysis has been used as a tool to quantify and discriminate the role of tectonics and eustasy in the Veneto and Friuli Basin, north-east Italy, using 17 sections distributed along east–west-trending outcrops of Oligo-Miocene deposits. The basin can be considered a two-phase foreland; first, during late Oligocene to Langhian with respect to the NW–SE-trending Dinaric Chain, and then with respect to the south-vergent South-Alpine Chain.The clastic succession is up to 4000 m thick, and was deposited in a generally shallow-marine to nonmarine environment. Subsidence diagrams reconstructed for each section and E–W subsidence profiles indicate a compound effect of the Dinaric and South-Alpine tectonics as well as interference with eustatic sea-level changes.During the Oligocene and the early Miocene, the cycles recognized within the basin approximately match sea-level curves, the inferred cyclicity being primarily eustatic. However, the westward migration of the sedimentary depocentre during the same interval of time indicates activity of Dinaric thrusts.From Burdigalian (20 Ma) onwards, differential subsidence between the northernmost and the southernmost sectors of the basin suggests initiation of South-Alpine uplift in the frontal parts. During Tortonian and early Messinian uplift, erosion and southward migration of the thrust system was associated with the progressive closure of the basin from open marine influence. During Messinian sea-level drop, up to 2500 m of alluvial sediments were deposited at the same time as the South-Alpine thrusts were emerging, as confirmed by progressive angular unconformities within the continental succession. 相似文献
10.
The solar cycle appears to be remarkably synchronized with the gravitational torques exerted by the tidally dominant planets Venus, Earth and Jupiter. Recently, a possible synchronization mechanism was proposed that relies on the intrinsic helicity oscillation of the current-driven Tayler instability which can be stoked by tidal-like perturbations with a period of 11.07 years. Inserted into a simple \(\alpha \)–\(\Omega \) dynamo model these resonantly excited helicity oscillations led to a 22.14 years dynamo cycle. Here, we assess various alternative mechanisms of synchronization. Specifically we study a simple time-delay model of Babcock–Leighton type dynamos and ask whether periodic changes of either the minimal amplitude for rising toroidal flux tubes or the \(\Omega \) effect could eventually lead to synchronization. In contrast to the easy and robust synchronizability of Tayler–Spruit dynamo models, our answer for those Babcock–Leighton type models is less propitious. 相似文献