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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physica D: Nonlinear Phenomena 6 (1982), S. 95-104 
    ISSN: 0167-2789
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-9136
    Keywords: Scattering ; wave propagation ; seismic waves ; core-mantle topography ; inhomogeneities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Statistical properties of small-scale inhomogeneities (wavelengths between 20 and 70 km) near the core-mantle boundary are inferred from scattered core waves. Observations of scattered core waves at large seismic arrays and worldwide networks indicate that the inhomogeneities have a global nature with similar characteristics. However, there may exist a few regions having markedly stronger or weaker strengths. Scattering by volumetric inhomogeneities of about 1% inP-wave velocity in the lower mantle or by about 300 m of topographic relief of the core-mantle boundary can explain the observations. At present it is not possible to rule out either of these two alternatives, or a combination of both.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2017-02-14
    Description: The southern central Chilean margin at the site of the largest historically recorded earthquake in the Valdivia region, in 1960 (Mw = 9.5), is part of the 5000-km-long active subduction system whose geodynamic evolution is controversially debated and poorly understood. Covering the area between 36° and 40°S, the oceanic crust is segmented by prominent fracture zones. The offshore forearc and its onshore continuation show a complex image with segments of varying geophysical character, and several fault systems active during the past 24 m.y. In autumn 2001, the project SPOC was organized to study the Subduction Processes Off Chile, with a focus on the seismogenic coupling zone and the forearc. The acquired seismic data crossing the Chilean subduction system were gathered in a combined offshore-onshore survey and provide new insights into the lithospheric structure and evolution of active margins with insignificant frontal accretion.
    Type: Article , NonPeerReviewed
    Format: text
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  • 4
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    In:  [Poster] In: SFB 574 Subduction Workshop, 04.-07.11.2010, Pucon, Chile .
    Publication Date: 2012-01-27
    Description: Chile is one of the most seismically active countries in the world with a M〉8 earthquake occurring approximately every ten years. The recent 27th February 2010 (Mw=8.8) earthquake released the energy accumulated in the Concepción-Constitución seismic gap, contained since the last 1835 earthquake. The hypocenter was located at the subduction interface of the Nazca plate under the South American plate, near the coast of Talcahuano, at a depth of 30 km. The rupture area extended approximately for 450 km long, from the Arauco Peninsula northwards to Pichilemu. Hundreds of aftershocks have taken place in the rupture area, the largest of which was the Pichilemu M=6.9 earthquake on 11th March. A volcano-surrounding network was installed in Llaima and Villarrica volcanoes in Southern Chile in November, 2009. Each network comprises one Broad Band station, one “Ocean” Bottom Station and three Short-Period stations arranged in a circular disposition. The seismological data recording at the two volcanoes is still ongoing until April 2011. Data examples and first results from the analysis of the data recorded from November, 2009 until April, 2010 are presented. The mainshock, foreshocks and aftershocks were retrieved, and are being separated from the local seismicity in the records. During the same time frame, volcanic events are identified to characterize the volcano seismicity at Llaima and Villarrica volcanoes, to correlate this activity with degassing emissions (SO2) measured with mini-DOAS. Any influence of the Maule earthquake on the volcanoes behaviour is also investigated based on the seismic records.
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 5
    Publication Date: 2019
    Description: 〈span〉〈div〉ABSTRACT〈/div〉Subduction processes at convergent margins produce complex temporal and spatial crustal displacements during different periods of the earthquake cycle. Satellite geodesy observations provide important clues to constrain kinematic models at subduction zones. Here, we analyze geodetic observations in central Chile, where two large earthquakes occurred: 2010 Mw 8.8 Maule and 2015 Mw 8.3 Illapel. We propose a model that considers the motion along both interfaces of the brittle subducting slab as the sources responsible for the movement of the crust in the different periods of the earthquake cycle. Using standard inversion techniques, we provide a consistent framework of the kinematic displacement during each period of the earthquake cycle. We show that during the interseismic period prior to the Maule and Illapel earthquakes, two patches of slip rate on the lower interface are determined. These patches are located just below the future hypocenters. Because the interseismic period corresponds to the loading process and the coseismic to the unloading process, it is interesting to note that the area where loading is stronger corresponds to the area where unloading is also strong. Furthermore, we show that the Maule earthquake causes a significant displacement on the lower interface, just below the epicenter of the future Illapel earthquake to the north, a few years later. We speculate that the interaction between motions along both interfaces is the key to understanding the evolution of stress and the occurrence of earthquakes at subduction zones. This framework improves the understanding of the observed loading and unloading processes and potential triggering between subduction earthquakes.〈/span〉
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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  • 6
    Publication Date: 2014-08-13
    Description: Non-linear elasticity has recently been considered as a source of scattering, therefore contributing to the coda of seismic waves, in particular for the case of explosive sources. This idea is analysed further here, theoretically solving the expression for the envelope of coda waves generated by a point moment tensor in order to compare with earthquake data. For weak non-linearities, one can consider each point of the non-linear medium as a source of scattering within a homogeneous and linear medium, for which Green's functions can be used to compute the total displacement of scattered waves. These sources of scattering have specific radiation patterns depending on the incident and scattered P or S waves, respectively. In this approach, the coda envelope depends on three scalar parameters related to the specific non-linearity of the medium; however these parameters only change the scale of the coda envelope. The shape of the coda envelope is sensitive to both the source time function and the intrinsic attenuation. We compare simulations using this model with data from earthquakes in Taiwan, with a good fit.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 7
    Publication Date: 2019
    Description: 〈span〉〈div〉ABSTRACT〈/div〉Subduction processes at convergent margins produce complex temporal and spatial crustal displacements during different periods of the earthquake cycle. Satellite geodesy observations provide important clues to constrain kinematic models at subduction zones. Here, we analyze geodetic observations in central Chile, where two large earthquakes occurred: 2010 Mw 8.8 Maule and 2015 Mw 8.3 Illapel. We propose a model that considers the motion along both interfaces of the brittle subducting slab as the sources responsible for the movement of the crust in the different periods of the earthquake cycle. Using standard inversion techniques, we provide a consistent framework of the kinematic displacement during each period of the earthquake cycle. We show that during the interseismic period prior to the Maule and Illapel earthquakes, two patches of slip rate on the lower interface are determined. These patches are located just below the future hypocenters. Because the interseismic period corresponds to the loading process and the coseismic to the unloading process, it is interesting to note that the area where loading is stronger corresponds to the area where unloading is also strong. Furthermore, we show that the Maule earthquake causes a significant displacement on the lower interface, just below the epicenter of the future Illapel earthquake to the north, a few years later. We speculate that the interaction between motions along both interfaces is the key to understanding the evolution of stress and the occurrence of earthquakes at subduction zones. This framework improves the understanding of the observed loading and unloading processes and potential triggering between subduction earthquakes.〈/span〉
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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  • 8
    Publication Date: 2016-04-04
    Description: We installed a dense, amphibious, temporary seismological network to study the seismicity and structure of the seismogenic zone in southern Chile between 37° and 39°S, the nucleation area of the great 1960 Chile earthquake. 213 local earthquakes with 14.754 onset times were used for a simultaneous inversion for the 1-D velocity model and precise earthquake locations. Relocated artificial shots suggest an accuracy of the earthquake hypocenter of about 1 km (horizontally) and 500 m (vertically). Crustal events along trench-parallel and transverse, deep-reaching faults reflect the interseismic transpressional deformation of the forearc crust due to the subduction of the Nazca plate. The transverse faults seems to accomplish differential lateral stresses between subduction zone segments. Many events situated in an internally structured, planar seismicity patch at 20 to 40 km depth near the coast indicate a stress concentration at the plate's interface at 38°S which might in part be induced by the fragmented forearc structure.
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2016-06-22
    Description: A temporal seismic network recorded local seismicity along a 130 km long segment of the transpressional dextral strike-slip Liquiñe-Ofqui fault zone (LOFZ) in southern Chile. Seventy five shallow crustal events with magnitudes up to M(tief)w 3.8 and depths shallower than 25 km were observed in an 11-month period mainly occurring in different clusters. Those clusters are spatially related to the LOFZ, to the volcanoes Chaitén, Michinmahuida and Corcovado, and to active faulting on secondary faults. Further activity along the LOFZ is indicated by individual events located in direct vicinity of the surface expression of the LOFZ. Focal mechanisms were calculated using deviatoric moment tensor inversion of body wave amplitude spectra which mostly yield strike-slip mechanisms indicating a NE–SW direction of the P-axis for the LOFZ at this latitude. The seismic activity reveals the present-day activity of the fault zone. The recent M(tief)w 6.2 event near Puerto Aysén, Southern Chile at 45.4°S on April 21, 2007 shows that the LOFZ is also capable of producing large magnitude earthquakes and therefore imposing significant seismic hazard to this region.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2018-02-15
    Description: In 2005 an amphibious seismic network was deployed on the Chilean forearc between 41.75°S and 43.25°S. 364 local events were observed in a 11-month period. A subset of the P and S arrival times were inverted for hypocentral coordinates, 1-D velocity structure and station delays. Main seismic activity occurred predominantly in a belt parallel to the coast of Chiloé Island in a depth range of 12–30 km presumably related to the plate interface. The 30° inclination of the shallow part of the Wadati-Benioff zone is similar to observations further north indicating that oceanic plate age is not controlling the subduction angle of the shallower part for the Chilean subduction zone. The down-dip termination of abundant intermediate depth seismicity at approximately 70 km depth seems to be related to the young age (and high temperature) of the oceanic plate. Crustal seismicity is associated with the Liquiñe-Ofqui fault zone and active volcanoes.
    Type: Article , PeerReviewed
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