Outlines of the adjustment of the finnish triangulation and the separate adjustment of the southern part of net     

J. Korhonen 《Journal of Geodesy》1961,61(1):265-282

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Study ofP-wave velocity below moho     

M. T. Porkka  H. Korhonen  K. Saviaro 《Pure and Applied Geophysics》1972,97(1):51-56

Summary Seismograms recorded during the Trans-Scandinavian Profile of 1969 at the stations Kajaani, Oulu, Maaselkä and Sodankylä are used to determine theP wave velocities for distances from 400 km to 1300 km. An apparent velocity of 8.50 km/s was found. After making a correction due to the curvature of the earth the velocity of about 8.40 km/s was obtained at an approximate depth of 80 km. Some comparisons are made with other results from Fennoscandian area.  相似文献   

Spectral development of microseism storms at the Oulu seismograph station,Finland     

H. Korhonen 《Pure and Applied Geophysics》1973,103(1):259-265

Summary In this study spectral development of microseisms at Oulu is discussed by means of power spectra computed from the recordings of a long period vertical seismograph. North Atlantic storm microseisms are found to be distinguished at peak frequencies in band 90–130 mHz while the main peaks of Norwegian microseisms occur at frequencies higher than 130 mHz. In both of these cases a low frequency side maximum is found at nearly the same frequencies as the main maximum in corresponding sea wave spectra. Fast moving storms associate with rapid changes in microseism spectra. A shift of peaks towards higher frequencies is found in connection with storm approach.  相似文献   

Present-day and future precipitation in the Baltic Sea region as simulated in a suite of regional climate models     

Erik Kjellström  Kimmo Ruosteenoja 《Climatic change》2007,81(1):281-291

Here we investigate simulated changes in the precipitation climate over the Baltic Sea and surrounding land areas for the period 2071–2100 as compared to 1961–1990. We analyze precipitation in 10 regional climate models taking part in the European PRUDENCE project. Forced by the same global driving climate model, the mean of the regional climate model simulations captures the observed climatological precipitation over the Baltic Sea runoff land area to within 15% in each month, while single regional models have errors up to 25%. In the future climate, the precipitation is projected to increase in the Baltic Sea area, especially during winter. During summer increased precipitation in the north is contrasted with a decrease in the south of this region. Over the Baltic Sea itself the future change in the seasonal cycle of precipitation is markedly different in the regional climate model simulations. We show that the sea surface temperatures have a profound impact on the simulated hydrological cycle over the Baltic Sea. The driving global climate model used in the common experiment projects a very strong regional increase in summertime sea surface temperature, leading to a significant increase in precipitation. In addition to the common experiment some regional models have been forced by either a different set of Baltic Sea surface temperatures, lateral boundary conditions from another global climate model, a different emission scenario, or different initial conditions. We make use of the large number of experiments in the PRUDENCE project, providing an ensemble consisting of more than 25 realizations of climate change, to illustrate sources of uncertainties in climate change projections.  相似文献   

The structure of the Baltic Shield region on the basis of DSS and earthquake data     

H. Korhonen  M. T. Porkka 《Pure and Applied Geophysics》1981,119(6):1093-1099

The lithospheric models obtained for the Baltic Shield by using deep seismic soundings are discussed and results from different parts of the shield are compared with models achieved by the investigation of surface waves and of P to S converted waves. The results are found to agree rather well with each other particularly with regard to the first interface (at a depth of 10–15 km) and the whole thickness of the crust (c. 40 km). The macroseismic focal depth determinations of regional earthquakes are correlated with lithospheric structure. The main maximum in the focal depth distributions of Finnish earthquakes occur at a depth of 10–12 km. The geographical distribution of the earthquake epicentres suggests several seismo-active zones in the northern Baltic Shield. One new finding in this field concerns the Lapland zone, which runs in a north-westerly direction.  相似文献   

Chemical spots on the surface of the strongly magnetic Herbig Ae star HD 101412     

S. P. Jrvinen  S. Hubrig  M. Schller  I. Ilyin  T. A. Carroll  H. Korhonen 《Astronomische Nachrichten》2016,337(3):329-338

Due to the knowledge of the rotation period and the presence of a rather strong surface magnetic field, the sharp‐lined young Herbig Ae star HD 101412 with a rotation period of 42 d has become one of the most well‐studied targets among the Herbig Ae stars. High‐resolution HARPS polarimetric spectra of HD 101412 were recently obtained on seven different epochs. Our study of the spectral variability over the part of the rotation cycle covered by HARPS observations reveals that the line profiles of the elements Mg, Si, Ca, Ti, Cr, Mn, Fe, and Sr are clearly variable while He exhibits variability that is opposite to the behaviour of the other elements studied. Since classical Ap stars usually show a relationship between the magnetic field geometry and the distribution of element spots, we used in our magnetic field measurements different line samples belonging to the three elements with the most numerous spectral lines, Ti, Cr, and Fe. Over the time interval covered by the available spectra, the longitudinal magnetic field changes sign from negative to positive polarity. The distribution of field values obtained using Ti, Cr, and Fe lines is, however, completely different compared to the magnetic field values determined in previous low‐resolution FORS 2 measurements, where hydrogen Balmer lines are the main contributors to the magnetic field measurements, indicating the presence of concentration of the studied iron‐peak elements in the region of the magnetic equator. Further, we discuss the potential role of contamination by the surrounding warm circumstellar matter in the appearance of Zeeman features obtained using Ti lines. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Recent observations of meteotsunamis on the Finnish coast     

Hilkka Pellikka  Jenni Rauhala  Kimmo K. Kahma  Tapani Stipa  Hanna Boman  Antti Kangas 《Natural Hazards》2014,74(1):197-215

We present four case studies of exceptional wave events of meteorological origin, observed on the Finnish coast in the summers of 2010 and 2011. Eyewitnesses report unusually rapid and strong sea-level variations (up to 1 m in 5–15 min) and strong oscillating currents during these events. High-resolution sea-level measurements confirm the eyewitness observations, but the oscillations recorded by tide gauges mostly have a considerably smaller amplitude. The oscillations coincide with sudden jumps in surface air pressure at coastal observation stations, related to the passage of squall lines or gust fronts. These fronts propagate above the sea at a resonant speed, allowing efficient energy transfer between the atmospheric disturbance and the sea wave that it generates. Thus, we interpret the observed sea-level oscillations as small meteotsunamis, long tsunami-like waves generated by meteorological processes and resonance effects.  相似文献   

Interaction of the Large Magellanic Cloud with the halo population and the companions of the Galaxy     

Mauri J. Valtonen  Kimmo A. Innanen  Leena Tähtinen 《Astrophysics and Space Science》1984,107(2):209-222

Numerical simulations have been performed in order to study the gravitational interaction between the outlying population of the Galaxy and the Large Magellanic Cloud (LMC). The following effects have been noted: (1) halo objects are partially removed from the orbital distance of the LMC such that a local minimum is created in the radial density profile; (2) a large number of halo objects go into escape orbits. This possibility makes the determination of the mass of the Galaxy by virial theorem arguments unreliable; (3) the orbit of the LMC decays faster than what one would expect on the basis of the classical dynamical friction calculation. The excess friction derives from three-body effects, which are not accounted for in the classical dynamical friction. Finally, the fates of globular clusters and dwarf galaxies near the Galaxy and the LMC are discussed.  相似文献   

New constraints on UHT metamorphism in the Eastern Ghats Province through the application of phase equilibria modelling and in situ geochronology     

F.J. Korhonen  A.K. Saw  C. Clark  M. Brown  S. Bhattacharya 《Gondwana Research》2011,20(4):764-781

High Mg–Al granulites from the Sunki locality in the central portion of the Eastern Ghats Province record evidence for the high-temperature peak and retrograde evolution. Peak metamorphic phase assemblages from two samples are garnet + orthopyroxene + quartz + ilmenite + melt and orthopyroxene + spinel + sillimanite + melt, respectively. Isochemical phase diagrams (pseudosections) based on bulk rock compositions calculated in the chemical system Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–Fe₂O₃ (NCKFMASHTO) and Al contents in orthopyroxene indicate peak UHT metamorphic conditions in excess of 960 °C and 9.7 kbar. Microstructures and the presence of cordierite interpreted to record the post-peak evolution show that the rocks underwent decompression and minor cooling from conditions of peak UHT metamorphism to conditions of ~ 900 °C at ~ 7.5 kbar. In situ U–Pb isotope analyses of monazite associated with garnet and cordierite using the Sensitive High Resolution Ion Microprobe (SHRIMP) yield a weighted mean ²⁰⁷Pb/²³⁵U age of ca. 980 Ma, which is interpreted to broadly constrain the timing of high-temperature monazite growth during decompression and melt crystallization at ~ 900–890 °C and 7.5 kbar. However, the range of ²⁰⁷Pb/²³⁵U monazite ages (from ca. 1014 Ma to 959 Ma for one sample and ca. 1043 Ma to 922 Ma for the second sample) suggest protracted monazite growth during the high-temperature retrograde evolution, and possibly diffusive lead loss during slow cooling after decompression. The results of the integrated petrologic and geochronologic approach presented here are inconsistent with a long time gap between peak conditions and the formation of cordierite-bearing assemblages at lower pressure, as proposed in previous studies, but are consistent with a simple evolution of a UHT peak followed by decompression and cooling.  相似文献   

Variations in the geomagnetic dipole moment during the Holocene and the past 50 kyr     

Mads Faurschou Knudsen  Peter Riisager  Fabio Donadini  Ian Snowball  Raimund Muscheler  Kimmo Korhonen  Lauri J. Pesonen 《Earth and Planetary Science Letters》2008,272(1-2):319-329

All absolute paleointensity data published in peer-reviewed journals were recently compiled in the GEOMAGIA50 database. Based on the information in GEOMAGIA50, we reconstruct variations in the geomagnetic dipole moment over the past 50  kyr, with a focus on the Holocene period. A running-window approach is used to determine the axial dipole moment that provides the optimal least-squares fit to the paleointensity data, whereas associated error estimates are constrained using a bootstrap procedure. We subsequently compare the reconstruction from this study with previous reconstructions of the geomagnetic dipole moment, including those based on cosmogenic radionuclides (¹⁰Be and ¹⁴C). This comparison generally lends support to the axial dipole moments obtained in this study. Our reconstruction shows that the evolution of the dipole moment was highly dynamic, and the recently observed rates of change (5% per century) do not appear unique. We observe no apparent link between the occurrence of archeomagnetic jerks and changes in the geomagnetic dipole moment, suggesting that archeomagnetic jerks most likely represent drastic changes in the orientation of the geomagnetic dipole axis or periods characterized by large secular variation of the non-dipole field. This study also shows that the Holocene geomagnetic dipole moment was high compared to that of the preceding  40  kyr, and that  4 · 10²²  Am² appears to represent a critical threshold below which geomagnetic excursions and reversals occur.  相似文献