| 1. |
- Abrehdary, Majid, et al.
(författare)
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Combined Moho parameters determination using CRUST1.0 and Vening Meinesz-Moritz model
- 2015
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Ingår i: Journal of Earth Science. - : Springer Science and Business Media LLC. - 1674-487X .- 1867-111X. ; 26:4, s. 607-616
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Tidskriftsartikel (refereegranskat)abstract
- According to Vening Meinesz-Moritz (VMM) global inverse isostatic problem, either the Moho density contrast (crust-mantle density contrast) or the Moho geometry can be estimated by solving a non-linear Fredholm integral equation of the first kind. Here solutions to the two Moho parameters are presented by combining the global geopotential model (GOCO-03S), topography (DTM2006) and a seismic crust model, the latter being the recent digital global crustal model (CRUST1.0) with a resolution of 1A(0)x1A(0). The numerical results show that the estimated Moho density contrast varies from 21 to 637 kg/m(3), with a global average of 321 kg/m(3), and the estimated Moho depth varies from 6 to 86 km with a global average of 24 km. Comparing the Moho density contrasts estimated using our leastsquares method and those derived by the CRUST1.0, CRUST2.0, and PREM models shows that our estimate agrees fairly well with CRUST1.0 model and rather poor with other models. The estimated Moho depths by our least-squares method and the CRUST1.0 model agree to 4.8 km in RMS and with the GEMMA1.0 based model to 6.3 km.
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| 2. |
- Aljinović, Dunja, et al.
(författare)
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Western Tethyan Epeiric Ramp Setting in the Early Triassic : An Example from the Central Dinarides (Croatia)
- 2018
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Ingår i: Journal of Earth Science. - : Springer Science and Business Media LLC. - 1674-487X .- 1867-111X. ; 29:4, s. 806-823
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Tidskriftsartikel (refereegranskat)abstract
- In the central part of the External Dinarides in Plavno, Croatia, near Knin, a remarkably thick (927.5 m) Early Triassic depositional sequence was investigated. The Plavno sequence starts in the EarlyGriesbachian and ends with a continuous transition into the Anisian strata. A complete 13C isotope curve has been achieved and combined with conodonts, bivalves and ammonoids to establish and correlate stage and substage boundaries. The δ13C curve is consistent with former studies. It displays a general increase from the Griesbachian to a prominent maximum beyond the +8‰ amplitude around the Dienerian-Smithian boundary (DSB), followed by a steep and continuous decline to low, negative values in the Smithian. Around the Smithian-Spathian boundary (SSB) a steep rise to a second maximum occurred. It is followed by a saw-tooth shaped decline in the Spathian and a similar increase to a peak at the Spathian-Anisian boundary (SAB). Sedimentologically, the Plavno sequence is interpreted as having been deposited on an extensive epeiric ramp under long-term transgressive conditions, sharing depositional characteristics of both the epeiric platform and the carbonate ramp. The entire Plavno sequence was deposited above the storm-wave base and was storm influenced. Three informal members are differentiated: 1) the dolostone member (Early Griesbachian); 2) the siliciclastic member (red-coloured shale, siltstone, sandstone with oolitic/bioclastic grainstone intercalations), which can be further divided into lower, middle and upper intervals (Late Griesbachian, Dienerian and Smithian); and 3) the mudstone member (grey lime mudstones, marls and calcisiltites with common ammonoids and gastropods-Spathian). The Plavno sequence is compared with other western Tethyan sections. Observed differences stem from local controls on deposition in the overall shallow marine environment.
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| 3. |
- Andersson, Fredrik, et al.
(författare)
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Frequency Extrapolation through Sparse Sums of Lorentzians
- 2014
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Ingår i: Journal of Earth Science. - : Springer Science and Business Media LLC. - 1867-111X .- 1674-487X. ; 25:1, s. 117-125
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Tidskriftsartikel (refereegranskat)abstract
- Sparse sums of Lorentzians can give good approximations to functions consisting of linear combination of piecewise continuous functions. To each Lorentzian, two parameters are assigned: translation and scale. These parameters can be found by using a method for complex frequency detection in the frequency domain. This method is based on an alternating projection scheme between Hankel matrices and finite rank operators, and have the advantage that it can be done in weighted spaces. The weighted spaces can be used to partially revoke the effect of finite band-width filters. Apart from frequency extrapolation the method provides a way of estimating discontinuity locations.
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| 4. |
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| 5. |
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| 6. |
- Rubino, J. German, et al.
(författare)
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Energy dissipation of seismic P- and S-waves in fluid-saturated rocks: An overview focusing on hydraulically connected fractures
- 2015
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Ingår i: Journal of Earth Science. - : Springer Science and Business Media LLC. - 1674-487X .- 1867-111X. ; 26, s. 785-790
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Tidskriftsartikel (refereegranskat)abstract
- An important characteristic of fractured rocks is their high seismic attenuation, which so far has been mainly attributed to wave-induced fluid flow (WIFF) between the fractures and the embedding matrix. The influence of fracture connectivity on seismic attenuation has, however, recently, only been investigated. Numerical compressibility and shear tests based on Biot’s quasi-static poro-elastic equations illustrate that an important manifestation of WIFF arises in the presence of fracture connectivity. The corresponding energy loss, which can be significant for both P- and S-waves, is mainly due to fluid flow within the connected fractures and is sensitive to the permeabilities as well as the lengths and intersection angles of the fractures. Correspondingly, this phenomenon contains valuable information on the governing hydraulic properties of fractured rocks and hence should be accounted for whenever realistic seismic models of such media are needed.
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| 7. |
- Tenzer, R., et al.
(författare)
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Theoretical deficiencies of isostatic schemes in modeling the crustal thickness along the convergent continental tectonic plate boundaries
- 2016
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Ingår i: Journal of Earth Science. - : China University of Geosciences. - 1674-487X .- 1867-111X. ; , s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The results of global and regional studies often show significant disagreement between the Moho depths determined using seismic and isostatic models. In this study, we estimate the differences between these two models in central Eurasia. The Vening Meinesz-Moritz (VMM) inverse problem of isostasy is utilized to determine the isostatic Moho depths. The estimated VMM Moho depths are then corrected for the sediment density contrast. The application of this correction improves the agreement between the isostatic and seismic Moho models. The existing discrepancies between the isostatic and seismic models are finally modeled by applying the non-isostatic correction, which accounts for the unmodelled mantle density heterogeneities and other geodynamic processes, which are not taken into account in classical isostatic models. Our results reveal that the non-isostatic correction still cannot fully describe mechanisms affecting the Moho geometry along the convergent continent-tocontinent tectonic plate boundaries occurring beneath Himalayas despite an overall good performance of the applied method.
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| 8. |
- Yousefi, Fazilat, et al.
(författare)
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Geochemical and Nd-Sr Isotopic Compositions of Hypabyssal Adakites in the Torud-Ahmad Abad Magmatic Belt, Northern Central Iran Zone : Analysis of Petrogenesis and Geodynamic Implications
- 2021
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Ingår i: Journal of Earth Science. - : Springer Nature. - 1674-487X .- 1867-111X. ; 32:6, s. 1428-1444
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Tidskriftsartikel (refereegranskat)abstract
- Eocene intermediate to felsic subvolcanic rocks of the Torud-Ahmad Abad magmatic belt (TAMB), in the northern part of the Central Iran zone, are exposed between the Torud and Ahmad Abad regions in South-Southeast Shahrood. These igneous rocks include hypabyssal dacite, trachyte, andesite, trachy-andesite, and basaltic andesite; they are mainly composed of phenocrysts and microcrystalline groundmass of pyroxene, amphibole, and plagioclase, with minor biotite and titanomagnetite; they form domal structures (plugs and stocks), dikes, and sills that intruded into Neoproterozoic to cogenetic Eocene volcano-sedimentary sequences. Based on isotopic analysis of these intermediate to acidic rocks, initial ratios of 143Nd/144Nd range from 0.512 775 to 0.512 893 and initial ratios of 87Sr/86Sr range from 0.703 746 to 0.705 314, with quite positive εNd(i) values of +3.69 to +6.00. They are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high-field strength elements, the SiO2 content is (52–62) wt.%, and Na2O content >3 wt.%, Al2O3 content >16 wt.%, Yb <1.8 ppm, and Y <18 ppm. These geological, geochemical, and Sr and Nd isotopic data are consistent with adakitic signatures originating by partial melting of the subducted Neo-Tethys oceanic slab (Sabzevar branch) and lithospheric suprasubduction zone mantle. The mantle signatures typifying the rapidly emplaced adakitic rocks (slab (high-silica adakite) and suprasubduction zone (low-silica adakite) melts) together with their locally voluminous extent are evidences that support a locally extensional geodynamic setting; and the evidence is consistent with an evolution to local transpression in the Late Eocene in this convergent margin arc environment to rifting (basalts to adakites) towards submarine conditions in the Neogene. © 2021, China University of Geosciences (Wuhan) and Springer-Verlag GmbH Germany, Part of Springer Nature.
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