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  • 1.
    Cherevatova, M.
    et al.
    Institute for Geophysics, University of Münster, 48149 Münster, Germany.
    Egbert, G. D.
    College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.
    Smirnov, M. Yu
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    A multi-resolution approach to electromagnetic modelling2018Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 214, nr 1, s. 656-671Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a multi-resolution approach for 3-D magnetotelluric forward modelling. Our approach is motivated by the fact that fine-grid resolution is typically required at shallow levels to adequately represent near surface inhomogeneities, topography and bathymetry, while a much coarser grid may be adequate at depth where the diffusively propagating electromagnetic fields are much smoother. With a conventional structured finite difference grid, the fine discretization required to adequately represent rapid variations near the surface is continued to all depths, resulting in higher computational costs. Increasing the computational efficiency of the forward modelling is especially important for solving regularized inversion problems. We implement a multi-resolution finite difference scheme that allows us to decrease the horizontal grid resolution with depth, as is done with vertical discretization. In our implementation, the multi-resolution grid is represented as a vertical stack of subgrids, with each subgrid being a standard Cartesian tensor product staggered grid. Thus, our approach is similar to the octree discretization previously used for electromagnetic modelling, but simpler in that we allow refinement only with depth. The major difficulty arose in deriving the forward modelling operators on interfaces between adjacent subgrids. We considered three ways of handling the interface layers and suggest a preferable one, which results in similar accuracy as the staggered grid solution, while retaining the symmetry of coefficient matrix. A comparison between multi-resolution and staggered solvers for various models shows that multi-resolution approach improves on computational efficiency without compromising the accuracy of the solution.

  • 2.
    Elming, Sten-åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Integrated seismic studies of the Baltic shield using data in the Gulf of Bothnia region1993Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 112, nr 3, s. 305-324Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the autumn of 1989 a co-operative experiment involving 12 research institutions in northwestern Europe collected 2268 km of deep seismic reflection profiles in the Gulf of Bothnia and the Baltic Sea. the 121 litre airgun array used for this profiling was also recorded by 62 muiticomponent land stations to provide coincident refraction surveys, fan-spreads, and 3-D seismic coverage of much of the Gulf of Bothnia. We thus have potentially both high-resolution impedance contrast images as well as more regional 3-D velocity models in both P- and S-waves. In the Bothnian Bay a south-dipping, non-reflective zone coincides with the conductive Archaean-Proterozoic boundary onshore in Finland. Between the Bothnian Bay and Bothnian Sea observed reflectivity geometries and velocity models at Moho depths suggest structures inherited from a 1.9Ga subduction zone; the upper crust here appears to have anomalously low velocity. Within the Bothnian Sea, reflectivity varies considerably beneath the metasedimentary/granitoid rocks of the Central Svecofennian Province (CSP) and the surrounding metavolcanic-arc rocks. Numerous dipping reflectors appear throughout the metavolcanic crust, whereas the CSP has little reflectivity. Wide-angle reflections indicate that the metasedimentary crust of the Bothnian Basin is 10 km thicker than the neighbouring Svecofennian subprovinces. Near the Åland archipelago Rapakivi granite plutons exhibit bright reflections, a contrast to the usual non-reflective plutons elsewhere in western Europe. Additional dipping reflections deep in the crust of this area may support models of rifting and crustal thinning during emplacement of the 1.70-1.54 Ga Rapakivi granites. Coeval gabbroic/anorthositic magmatism may explain the high reflectivity and high velocity of these plutons. the c. 1.25 Ga mafic sills and feeder dykes of the Central Scandinavian Dolerite Group also produce clear reflections on both near- and far-offset seismic sections. Continued modelling will produce better velocity models of the crust and better constrained contour maps of crustal thickness in this part of the Baltic shield.

  • 3.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bylund, Göran
    Palaeomagnetism and the Siljan impact structure, central Sweden1991Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 105, nr 3, s. 757-770Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A palaeomagnetic study of rocks, from inside and outside the impact structure has been carried out, with the aim of identifying natural remanent magnetizations (NRMs) related to the impact event. Three different directions of magnetizations, not recognized elsewhere, were identified within the central part of the structure. These three magnetizations are defined in terms of coercivity and blocking temperature. The implications of the results are discussed in relation to ages obtained from Ar-Ar dating of impact melt

  • 4.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    D'Agrella-Filho, M.S.
    Universidade de São Paulo.
    Page, L.M.
    University of Lund.
    Tohver, E.
    School of Earth and Geographical Sciences, University of Western Australia, Crawley.
    Trindade, R. I. F.
    Universidade de São Paulo.
    Pacca, I.I.G.
    Universidade de São Paulo.
    Geraldes, M.C.
    Faculdade de Geologia, Universidade do Estado do Rio de Janeiro.
    Teixeira, W.
    Instituto de Geociências, Universidade de São Paulo.
    A palaeomagnetic and Ar-40/Ar-39 study of late precambrian sills in the SW part of the Amazonian craton: Amazonia in the Rodinia reconstruction2009Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 178, nr 1, s. 106-122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new key palaeomagnetic pole (Plat. = 64.3°S, Plon. = 271.0°E, N = 14, A95= 9.2°; Q = 5) is calculated from a primary magnetization isolated in early Neoproterozoic Aguapei basic sills and dykes hosted by 1.3-1.0 Ga sedimentary rocks from the southwestern part of the Amazon craton. The characteristic remanence carried by stable, pseudo-single domain titanomagnetite shows two antipodal polarities that pass a reversals test. Magnetic anisotropy for most sites shows fabric orientations that are typical of sills, with horizontal magnetic foliations concordant to the flat-lying bedding of the host sedimentary rocks. 40Ar/39Ar analyses for one of the sills reveal a well-defined plateau age at 981 ± 2 Myr. A tectonic reconstruction for Amazonia relative Laurentia based on this new pole 'is consistent with' a position of the present northwestern part of Amazonia attached with eastern Laurentia close to Greenland at ca. 981 Ma. On basis of palaeomagnetic and geological data, we propose a scenario where Amazonia moved northeastwards along the present southeast coast of Laurentia from ca. 1200 to 980 Ma. By 980 Ma, Amazonia is placed alongside Laurentia and Baltica, in a position similar to other reconstructions of Rodinia but with a significantly different orientation.

  • 5.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Layer, P.
    Geophysical Institute, University of Alaska.
    Ubieta, K.
    Centro de Investigaciones Geoscientificas (CIGEO), the Autonomous University of Nicaragua (UNAN), Managua.
    A palaeomagnetic study and age determinations of Tertiary rocks in Nicaragua, Central America2001Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 147, nr 2, s. 294-309Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Palaeomagnetic, K-Ar and Ar40/Ar39 measurements have been made to elucidate Nicaragua's plate tectonic history. These show that the Nicaraguan Highland rotated 90° counterclockwise between 30 and 18 Myr ago, but the Pacific Coastal Plain has not rotated.A lack of data has prevented a direct comparison with the tectonic history of adjacent areas, in particular, the Chortis Block, which is the part of the Caribbean Plate that is geologically most closely related to the Nicaraguan Highland. However, our data suggest that the Caribbean Plate in this part of Central America was not consolidated until c. 15 Ma.

  • 6.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Maokhar, M.O.
    Razi University, Department of Physics, Faculty of Basic Sciences.
    Layer, P.
    University of Alaska, Institute for Geophysics, Fairbanks.
    Donadini, F.
    Scripps Institution of Oceanography, La Jolla, United States of America.
    Uplift deduced from remanent magnetization of a proterozoic basic dyke and the baked country rock in the Hoting area, central Sweden: a palaeomagnetic and Ar-40/Ar-39 study2009Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 179, nr 1, s. 59-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Remanent magnetization in dyke contact zones in the Hoting area of the Fennoscandian Shield in the central part of Sweden has been studied in order to establish the ambient temperature of the host rock and the depth of burial of the present erosion surface at the time of intrusion. A positive baked contact test for two Subjotnian dykes demonstrates the primary nature of the dyke magnetization. From the magnetic properties and the palaeomagnetic data, it can be concluded that the overprinting in the hybrid zone of one of the basic dykes is a partial thermoremanent magnetization. Reliable results were also obtained from a palaeointensity study of samples from the hybrid zone in the baked host rock. The study was performed in the laboratories at Luleå and at Scripps and a mean intensity of the Earth's magnetic field of 5.8 ± 1.9 μT was determined. The maximum temperature due to the dyke intrusion in the hybrid zone has been defined and from that an ambient temperature of 375 °C in the host rock at the time of intrusion has been calculated. This calculated temperature is not contradicted by the 40Ar/39Ar data. A palaeothermal gradient in the crust at ca. 1.6 Ga is calculated at ca. 34 °C km-1 and yields a depth of burial of the present erosion surface at ca. 10.4 km. This implies an uplift rate of 0.65 km (100 Ma)-1. A slow cooling of the gabbroic host rock (ca. 3.5 °C Ma-1) has been calculated from the difference in the U-Pb age of zircon (1.786 ± 0.010 Ga) and the 40Ar/39Ar biotite ages (1.648 ± 0.012 Ga; 1614 ± 0.024 Ga) of this study. This slow cooling resulted in a palaeomagnetic age of ca. 1.7 Ga for the gabbro, which is also the age of the determined palaeointensity. The calculated ca. 1.614 Ga palaeomagnetic pole from the basic dykes fulfils most of the criteria for a reliable pole and may be regarded as a new key-pole for Fennoscandia.

  • 7.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Rasmussen, Thorkild Maack
    Danmarks og Grønlands Geologiske Undersøgelse, GEUS.
    Results of magnetotelluric and gravimetric measurements in western Nicaragua, central America1997Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 128, nr 3, s. 647-58Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies a ca. 170 km long traverse running from the Pacific coast of Nicaragua in the west to the Nicaraguan Highland in the east. This part of Nicaragua is characterized by sedimentary rocks of the Pacific Coastal Plain, separated from the Tertiary volcanic rocks of the Highland by the NW-SE-trending Nicaraguan Depression. The purpose of this study is to provide electric conductivity and density constraints on geological crustal structures along the transect. This may then serve as a base for the understanding of the tectonic evolution of this part of Central America. Questions to be answered are: (1) is the Pacific coastal province an accreted terrane? (2) What is the character of the depression? Is this a hidden contact between an accreted terrane and the continental Chortis block? (3) If so, is there a different physical signature for the crust of the Pacific province compared to that of the Highlands?

  • 8.
    Jokat, Wilfried
    et al.
    Ayred Wegener Institute for Polar and Marine Research.
    Weigelt, Estella
    Ayred Wegener Institute for Polar and Marine Research.
    Kristoffersen, Yngve
    University of Bergen, Institut for Solid Earth Physics.
    Rasmussen, Thorkild Maack
    University of Uppsala.
    Schöne, Tilo
    University of Uppsala.
    New geophysical results from the south‐western Eurasian Basin (Morris Jesup Rise, Gakkel Ridge, Yermak Plateau) and the Fram Strait1995Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 123, nr 2, s. 601-610Artikkel i tidsskrift (Fagfellevurdert)
  • 9.
    Jokat, Wilfried
    et al.
    Ayred Wegener Institute for Polar and Marine Research.
    Weigelt, Estella
    Ayred Wegener Institute for Polar and Marine Research.
    Kristoffersen, Yngve
    University of Bergen, Institut for Solid Earth Physics.
    Rasmussen, Thorkild Maack
    University of Uppsala.
    Schöne, Tilo
    University of Uppsala.
    New insights into the evolution of the Lomonosov Ridge and the Eurasian Basin1995Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 122, nr 2, s. 378--392Artikkel i tidsskrift (Fagfellevurdert)
  • 10.
    Ju, Ma
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi. Department of Mining Engineering, North China University of Science and Technology, Tangshan.
    Dineva, Savka
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Cesca, Simone
    GFZ German Research Centre for Geosciences Potsdam, Germany.
    Heimann, Sebastian
    GFZ German Research Centre for Geosciences Potsdam, Germany.
    Moment tensor inversion with three-dimensional sensor configuration of mining induced seismicity (Kiruna mine, Sweden)2018Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 213, nr 3, s. 2147-2160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mining induced seismicity is an undesired consequence of mining operations, which poses significant hazard to miners and infrastructures and requires an accurate analysis of the rupture process. Seismic moment tensors of mining-induced events help to understand the nature of mining-induced seismicity by providing information about the relationship between the mining, stress redistribution and instabilities in the rock mass. In this work, we adapt and test a waveform-based inversion method on high frequency data recorded by a dense underground seismic system in one of the largest underground mines in the world (Kiruna mine, Sweden). A stable algorithm for moment tensor inversion for comparatively small mining induced earthquakes, resolving both the double-couple and full moment tensor with high frequency data, is very challenging. Moreover, the application to underground mining system requires accounting for the 3-D geometry of the monitoring system. We construct a Green's function database using a homogeneous velocity model, but assuming a 3-D distribution of potential sources and receivers. We first perform a set of moment tensor inversions using synthetic data to test the effects of different factors on moment tensor inversion stability and source parameters accuracy, including the network spatial coverage, the number of sensors and the signal-tonoise ratio. The influence of the accuracy of the input source parameters on the inversion results is also tested. Those tests show that an accurate selection of the inversion parameters allows resolving the moment tensor also in the presence of realistic seismic noise conditions. Finally, the moment tensor inversion methodology is applied to eight events chosen from mining block #33/34 at Kiruna mine. Source parameters including scalar moment, magnitude, double-couple, compensated linear vector dipole and isotropic contributions as well as the strike, dip and rake configurations of the double-couple term were obtained. The orientations of the nodal planes of the double-couple component in most cases vary from NNW to NNE with a dip along the ore body or in the opposite direction.

  • 11.
    Juhlin, C.
    et al.
    Uppsala University.
    Elming, Sten-åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mellqvist, C.
    SGAB Analytica.
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Wikström, A.
    Geological Survey of Sweden.
    Crustal reflectivity near the Archean-Proterozoic boundary in northern Sweden and implications for the tectonic evolution of the area2002Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 150, nr 1, s. 180-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sm–Nd isotope ratios of 1.9–1.8 Ga granitoids delineate the Archaean–Proterozoic boundary in northern Sweden, an important feature in the Fennoscandian Shield. The boundary strikes approximately WNW–ESE and is defined as a c. 20 km wide zone with juvenile Palaeoproterozoic rocks to the SSW and Archaean and Proterozoic rocks, derived to a large extent from Archaean sources, to the NNE. It therefore constitutes the strongly reworked margin of the old Archaean craton. Extrapolation of the boundary offshore into the Bothnian Bay and correlation with the marine reflection seismic BABEL Lines 2 and 3/4 indicates that the boundary dips to the south-southwest, consistent with interpretation of the Sm–Nd data. In order to tie the BABEL results with onshore surface geology and obtain detailed images of the uppermost crust a short (30 km of subsurface coverage) pilot profile was acquired in the Luleå area of northern Sweden during August 1999. The profile consisted of a high-resolution shallow component (1 kg shots) and a lower-resolution deep component (12 kg shots). Both components image most of the reflective crust, with the deep component providing a better image below 10 s. Comparison of signal penetration curves with data acquired over the Trans-Scandinavian Igneous Belt (a large batholith) indicate the transparent nature of the crust there to be caused by geological factors, not acquisition parameters. Lower crustal reflectivity patterns on the Luleå test profile are similar to those observed on the BABEL lines, suggesting the same lower crust onshore as offshore. Interpreted Archaean reflective upper crust in the NE extends below more transparent Proterozoic crust in the SW. This transparent crust contains a number of high-amplitude reflectors that may represent shear zones and/or mafic rock within granite intrusions. A marked boundary in the magnetic field in the SW has been interpreted as being the result of a gently west-dipping contact zone between meta-sediments and felsic volcanic rocks, however, the seismic data indicate a near-vertical structure in this area. By correlating the onshore and offshore seismic data we have better defined the location of the Archaean–Proterozoic boundary on the BABEL profiles. Our new interpretation of the crustal structure along the northern part of the BABEL Line 2 shows a more bi-vergent geometry than previous interpretations. Comparison of the re-interpreted crustal structure in northern Sweden with that found in the Middle Urals shows several similarities, in particular the accretion of a series of arcs to a stable craton. Based on this similarity and geological data, we deduce that a continental arc accreted to the southwestern margin of the Archaean craton at c. 1.87 Ga. Shortly thereafter, the Skellefte island arc underthrust the continental arc owing to a collision further to the southwest resulting in the bi-vergent crustal structure observed today.

  • 12. Parasnis, Dattatray
    Effect of a uniform overburden on the passage of a thermal wave and the temperatures in the undelying rock1976Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 46, nr 1, s. 189-192Artikkel i tidsskrift (Fagfellevurdert)
  • 13. Parasnis, Dattatray
    Geothermal flow and phenomena in two Swedish localities north of the Arctic circle1982Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 71, nr 3, s. 545-554Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Temperature measurements in eight holes reaching vertical depths between 287 and 1100m below ground surface in the Malmberget area (lat. 67° 10' N, long. 20° 40' E Gr.) and the Kiruna area (lat. 67° 52' N, long. 20° 9' E Gr.) in the Swedish Precambrian are reported. The mean equilibrium heat flow in this part of the Swedish shield after climatic correction is 52.6 ± 1.7mWm-2. The mean uncorrected heat flow is 46.6 mWm-2. Comparison with other shield areas shows that in common with the S. African and Indian shields, the north Swedish shield has a greater heat flow than the remaining shield areas of the world.

  • 14.
    Parasnis, Dattatray
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Temperature phenomena and heat flow estimates in two precambrian ore-bearing areas in north Sweden1975Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 43, nr 2, s. 531-554Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Temperature measurements in 17 drillholes reaching vertical depths between 365 and 780 m below ground surface in the Skellefte area (lat. 65° 52deg;N, long. 20° 20° E Gr) and Aitik area (lat. 67° 5deg;N, long. 21° E Gr) in the Swedish precambrian are reported. The absolute accuracy of the measurements was about 0.03°C and the relative one about 0.005°C. A large number of thermal diffusivity measurements were made on rock samples from the two areas in order to estimate the correction to the observed steady geothermal gradients due to climatic amelioration at the end of the Pleistocene. The corrected gradients are between 0.01266°C m-1 and 0.01485°C m-1 (Skellefte) and between 0.01684°C m-1 and 0.02268°C m-1 (Aitik). The diffusivity measurements were supplemented by thermal conductivity determinations on 265 drillcore samples from the different rock formations in the holes.The undisturbed heat flow in the Skellefte area is found to be 48.7 mW m-2 and that in the Aitik area to be 49.8 mW m-2. Distortion of the heat flow due to a sulphide ore in the Skellefte area is demonstrated. The heat flow through the Långsele ore in this area is of the order of 70 mW m-2.

  • 15.
    Roten, Daniel
    et al.
    ETH Zurich, Institute of Geophysics.
    Fäh, Donat
    ETH Zurich, Institute of Geophysics.
    Bonilla, Luis Fabian
    Institut de Radioprotection et de Sûreté Nucléaire, BP 17, Fontenay-aux-Roses Cedex.
    Alvarez-Rubio, Sonia
    ETH Zurich, Institute of Geophysics.
    Weber, Toni M.
    ETH Zurich, Institute for Geotechnical Engineeering.
    Laue, Jan
    ETH Zurich, Institute for Geotechnical Engineeering.
    Estimation of non-linear site response in a deep Alpine valley2009Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 178, nr 3, s. 1597-1613Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We simulate non-linear behaviour of soils during strong ground motion in the Rhône valley in southern Switzerland. Previous studies of the site response using weak ground motion, ambient noise and linear 3-D FD simulations suggest that the 2-D structure of the basin will lead to amplification factors of up to 12 in the frequency band between 0.5 and 10 Hz. To estimate the importance of non-linear soil behaviour during strong ground motion in the Rhône valley we simulate the response of a superficial soft layer with a fully non-linear 1-D finite difference code. The non-linear wave propagator is based on an effective stress constitutive soil model capable of predicting pore pressure evolution due to shear. We determine the required dilatancy parameters from laboratory analysis of soil samples using cyclic triaxial tests. In order to include the effect of the strong 2-D structure in our non-linear analysis synthetic seismograms are convolved with the transfer function of the basin and then propagated through a 1-D non-linear layer. We find that reduced amplification due to soil non-linearity can be expected at rock accelerations above 0.5 ms-2, and that de-amplification occurs at ground motion levels of approximately 2 ms-2. Nevertheless, the spectral accelerations simulated forthe valley centre are still exceeding the design spectra at about 0.5 Hz for magnitudes above 6.0, which reflects the strong amplification of ground motion by the deep 2-D resonance of the basin. For frequencies above 1 Hz the design spectra are generally in agreement with the strongest simulated accelerations. We evaluate the occurrence of soil failure using the 5 per cent strain criterion as a function of hypocentral distance and magnitude. Results confirm observations of liquefaction reported after the 1855 Mw 6.4 earthquake of Visp, and they suggest that soil liquefaction may occur at distances beyond those predicted by empirical relations in the valley. Near the basin edge, however, the simulated liquefaction occurrence agrees with the empirical relations. These results suggest that the response of the whole structure needs to be simulated in order to estimate the non-linear seismic response of complex basins like the Rhône valley

  • 16.
    Stich, Daniel
    et al.
    Instituto Andaluz de Geofisica, Universidad de Granada, Observatorio de Cartuja, Granada.
    Batlló, Josep
    Departamento de Matemática Aplicada I, Universitat Politècnica de Catalunya.
    Morales, José A.
    Andaluz de Geofisica, Universidad de Granada, Observatorio de Cartuja, Granada.
    Macià, Ramon
    Departamento de Matemática Aplicada II, Universitat Politècnica de Catalunya.
    Dineva, Savka
    Source parameters of the M w = 6.1 1910 Adra earthquake (southern Spain)2003Inngår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 155, nr 2, s. 539-546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We examine and model analogue recordings from 6 early mechanical seismographs for the 1910 June 16 earthquake at Adra, Southern Spain. Modern standard, time-domain analysis techniques were applied to the historical data to estimate the source parameters of the event: The regional sparse network data were inverted for the deviatoric seismic moment tensor. The best moment tensor solution corresponds to a M o = 1.50 . 10 18 Nm, M w 6.1 oblique strike-slip event at 16 km depth. Our preferred faulting solution is: strike 122°, dip 80° rake - 137°, in very good agreement with available neo- and seismotectonic data. The source time function of this earthquake was estimated by deconvolving recordings of a M w 5.5 aftershock that occurred the same day. The time function indicates a total rupture time of 4.5 s, corresponding to estimates for mainshock rupture length of 12 km, and stress drop of 29 bar.

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