TY - JOUR A1 - Pesicek, J. D. A1 - Engdahl, E. R. A1 - Thurber, C. H. A1 - DeShon, H. R. A1 - Lange, Dietrich T1 - Mantle subducting slab structure in the region of the 2010 M8.8 Maule earthquake (30-40 degrees S), Chile JF - Geophysical journal international N2 - We present a new tomographic model of the mantle in the area of the 2010 M8.8 Maule earthquake and surrounding regions. Increased ray coverage provided by the aftershock data allows us to image the detailed subducting slab structure in the mantle, from the region of flat slab subduction north of the Maule rupture to the area of overlapping rupture between the 1960 M9.5 and the 2010 M8.8 events to the south. We have combined teleseismic primary and depth phase arrivals with available local arrivals to better constrain the teleseismic earthquake locations in the region, which we use to conduct nested regionalglobal tomography. The new model reveals the detailed structure of the flat slab and its transition to a more moderately dipping slab in the Maule region. South of the Maule region, a steeply dipping relic slab is imaged from similar to 200 to 1000 km depth that is distinct from the moderately dipping slab above it and from the more northerly slab at similar depths. We interpret the images as revealing both horizontal and vertical tearing of the slab at similar to 38 degrees S to explain the imaged pattern of slab anomalies in the southern portion of the model. In contrast, the transition from a horizontal to moderately subducting slab in the northern portion of the model is imaged as a continuous slab bend. We speculate that the tearing was most likely facilitated by a fracture zone in the downgoing plate or alternatively by a continental scale terrane boundary in the overriding plate. KW - Seismicity and tectonics KW - Seismic tomography KW - Subduction zone processes Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-246X.2012.05624.x SN - 0956-540X VL - 191 IS - 1 SP - 317 EP - 324 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Förster, Hans-Jürgen A1 - Tischendorf, Gerhard A1 - Rhede, Dieter A1 - Naumann, R. A1 - Gottesmann, Bärbel A1 - Lange, W T1 - Cs-rich lithium micas and Mn-rich lithian siderophyllite in miarolitic NYF pegmatites of the Konigshain granite, Lausitz, Germany N2 - Annite and Fe-rich siderophyllite constitute the rock-forming micas in the late-Variscan composite granite pluton of Konigshain, Lausitz, Germany. This multiphase pluton is composed of three fractionated, but not chemically specialized monzogranite types, which contain lithophile elements such as Li, Rb, Cs, Sn, and F in average quantities. Abundant miarolitic pegmatites of the NYF family with a broad diversity of rare minerals occur in the apical part of the pluton. These pegmatitic cavities locally contain di- and trioctabedral micas as well as cation-deficient micas. Trioctahedral micas comprise F-rich manganoan lithian siderophyllite to manganoan zinnwaldite, zinnwaldite, and minor lepidolite. The formula [calculated on the basis of 22 anion valencies and 2 (F + OH + Cl)] of the most Mn-rich siderophyllite is (K0.85Rb0.08Na0.04)(0.97)(Al0.99Li0.91Fe0.51Mn0.42Ti0.01Zn0.01)(2.85) (Si3.21Al0.79)(4)O- 10(F1.80OH0.19Cl0.01)(2). This mica constitutes one of the most Mn-rich siderophyllite compositions reported to date. The lithium micas poorer in Mn are distinguished by elevated concentrations of Rb (up to 2.5 wt % Rb2O), CS (UP to 1.2 wt % Cs2O), and F (up to 9.6 wt %). This fluorine content is probably consistent with the maximum possible F occupation of 2 of the (F,OH,Cl)-site. The structural formula of the most Li-rich lepidolite is (K0.83Rb0.07Cs0.03)(0.93) (Li1.62Al1.00Fe0.38)(3.00)(Si3.62Al0.38)(4) O-10(F1.91OH0.09)(2). During hydrothermal alteration, lepidolite and zinnwaldite became partially depleted in K, Li, Rb, Cs, and F and gradually transformed into cation-deficient micas (lithian phengite to illite of phengitic affinity) Y1 - 2005 ER - TY - JOUR A1 - Hetenyi, Gyorgy A1 - Molinari, Irene A1 - Clinton, John A1 - Bokelmann, Gotz A1 - Bondar, Istvan A1 - Crawford, Wayne C. A1 - Dessa, Jean-Xavier A1 - Doubre, Cecile A1 - Friederich, Wolfgang A1 - Fuchs, Florian A1 - Giardini, Domenico A1 - Graczer, Zoltan A1 - Handy, Mark R. A1 - Herak, Marijan A1 - Jia, Yan A1 - Kissling, Edi A1 - Kopp, Heidrun A1 - Korn, Michael A1 - Margheriti, Lucia A1 - Meier, Thomas A1 - Mucciarelli, Marco A1 - Paul, Anne A1 - Pesaresi, Damiano A1 - Piromallo, Claudia A1 - Plenefisch, Thomas A1 - Plomerova, Jaroslava A1 - Ritter, Joachim A1 - Rumpker, Georg A1 - Sipka, Vesna A1 - Spallarossa, Daniele A1 - Thomas, Christine A1 - Tilmann, Frederik A1 - Wassermann, Joachim A1 - Weber, Michael A1 - Weber, Zoltan A1 - Wesztergom, Viktor A1 - Zivcic, Mladen A1 - Abreu, Rafael A1 - Allegretti, Ivo A1 - Apoloner, Maria-Theresia A1 - Aubert, Coralie A1 - Besancon, Simon A1 - de Berc, Maxime Bes A1 - Brunel, Didier A1 - Capello, Marco A1 - Carman, Martina A1 - Cavaliere, Adriano A1 - Cheze, Jerome A1 - Chiarabba, Claudio A1 - Cougoulat, Glenn A1 - Cristiano, Luigia A1 - Czifra, Tibor A1 - Danesi, Stefania A1 - Daniel, Romuald A1 - Dannowski, Anke A1 - Dasovic, Iva A1 - Deschamps, Anne A1 - Egdorf, Sven A1 - Fiket, Tomislav A1 - Fischer, Kasper A1 - Funke, Sigward A1 - Govoni, Aladino A1 - Groschl, Gidera A1 - Heimers, Stefan A1 - Heit, Ben A1 - Herak, Davorka A1 - Huber, Johann A1 - Jaric, Dejan A1 - Jedlicka, Petr A1 - Jund, Helene A1 - Klingen, Stefan A1 - Klotz, Bernhard A1 - Kolinsky, Petr A1 - Kotek, Josef A1 - Kuhne, Lothar A1 - Kuk, Kreso A1 - Lange, Dietrich A1 - Loos, Jurgen A1 - Lovati, Sara A1 - Malengros, Deny A1 - Maron, Christophe A1 - Martin, Xavier A1 - Massa, Marco A1 - Mazzarini, Francesco A1 - Metral, Laurent A1 - Moretti, Milena A1 - Munzarova, Helena A1 - Nardi, Anna A1 - Pahor, Jurij A1 - Pequegnat, Catherine A1 - Petersen, Florian A1 - Piccinini, Davide A1 - Pondrelli, Silvia A1 - Prevolnik, Snjezan A1 - Racine, Roman A1 - Regnier, Marc A1 - Reiss, Miriam A1 - Salimbeni, Simone A1 - Santulin, Marco A1 - Scherer, Werner A1 - Schippkus, Sven A1 - Schulte-Kortnack, Detlef A1 - Solarino, Stefano A1 - Spieker, Kathrin A1 - Stipcevic, Josip A1 - Strollo, Angelo A1 - Sule, Balint A1 - Szanyi, Gyongyver A1 - Szucs, Eszter A1 - Thorwart, Martin A1 - Ueding, Stefan A1 - Vallocchia, Massimiliano A1 - Vecsey, Ludek A1 - Voigt, Rene A1 - Weidle, Christian A1 - Weyland, Gauthier A1 - Wiemer, Stefan A1 - Wolf, Felix A1 - Wolyniec, David A1 - Zieke, Thomas T1 - The AlpArray seismic network BT - a large-scale european experiment to image the alpine orogen JF - Surveys in Geophysics N2 - The AlpArray programme is a multinational, European consortium to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps-Apennines-Carpathians-Dinarides orogenic system. The AlpArray Seismic Network has been deployed with contributions from 36 institutions from 11 countries to map physical properties of the lithosphere and asthenosphere in 3D and thus to obtain new, high-resolution geophysical images of structures from the surface down to the base of the mantle transition zone. With over 600 broadband stations operated for 2 years, this seismic experiment is one of the largest simultaneously operated seismological networks in the academic domain, employing hexagonal coverage with station spacing at less than 52 km. This dense and regularly spaced experiment is made possible by the coordinated coeval deployment of temporary stations from numerous national pools, including ocean-bottom seismometers, which were funded by different national agencies. They combine with permanent networks, which also required the cooperation of many different operators. Together these stations ultimately fill coverage gaps. Following a short overview of previous large-scale seismological experiments in the Alpine region, we here present the goals, construction, deployment, characteristics and data management of the AlpArray Seismic Network, which will provide data that is expected to be unprecedented in quality to image the complex Alpine mountains at depth. KW - Seismology KW - Alps KW - Seismic network KW - Geodynamics KW - Seismic imaging KW - Mountain building Y1 - 2018 U6 - https://doi.org/10.1007/s10712-018-9472-4 SN - 0169-3298 SN - 1573-0956 VL - 39 IS - 5 SP - 1009 EP - 1033 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Collings, R. A1 - Rietbrock, Andreas A1 - Lange, Dietrich A1 - Tilmann, F. A1 - Nippress, Stuart A1 - Natawidjaja, D. T1 - Seismic anisotropy in the sumatra subduction zone JF - Journal of geophysical research : Solid earth N2 - An important tool for understanding deformation occurring within a subduction zone is the measurement of seismic anisotropy through observations of shear wave splitting (SWS). In Sumatra, two temporary seismic networks were deployed between December 2007 and February 2009, covering the fore arc between the fore-arc islands to the back arc. We use SKS and local SWS measurements to determine the type, amount, and location of anisotropy. Local SWS measurements from the fore-arc islands exhibit trench-parallel fast directions which can be attributed to shape preferred orientation of cracks/fractures in the overriding sediments. In the Sumatran Fault region, the predominant fast direction is fault/trench parallel, while in the back-arc region it is trench perpendicular. The trench-perpendicular measurements exhibit a positive correlation between delay time and raypath length in the mantle wedge, while the fault-parallel measurements are similar to the fault-parallel fast directions observed for two crustal events at the Sumatran Fault. This suggests that there are two layers of anisotropy: one due to entrained flow within the mantle wedge and a second layer within the overriding crust due to the shear strain caused by the Sumatran Fault. SKS splitting results show a NNW-SSE fast direction with delay times of 0.8-3.0s. The fast directions are approximately parallel to the absolute plate motion of the subducting Indo-Australian Plate. The small delay times exhibited by the local SWS (0.05-0.45s), in combination with the large SKS delay times, suggest that the anisotropy generating the teleseismic SWS is dominated by entrained flow in the asthenosphere below the slab. KW - Sumatra KW - Anisotropy KW - Shear wave splitting KW - Subduction zone KW - Mantle rheology Y1 - 2013 U6 - https://doi.org/10.1002/jgrb.50157 SN - 2169-9313 SN - 2169-9356 VL - 118 IS - 10 SP - 5372 EP - 5390 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Collings, R. A1 - Lange, Dietrich A1 - Rietbrock, Andreas A1 - Tilmann, F. A1 - Natawidjaja, D. A1 - Suwargadi, B. A1 - Miller, M. A1 - Saul, Joschim T1 - Structure and seismogenic properties of the Mentawai segment of the Sumatra subduction zone revealed by local earthquake traveltime tomography JF - Journal of geophysical research : Solid earth N2 - On 12 September 2007, an M-w 8.4 earthquake occurred within the southern section of the Mentawai segment of the Sumatra subduction zone, where the subduction thrust had previously ruptured in 1833 and 1797. Traveltime data obtained from a temporary local seismic network, deployed between December 2007 and October 2008 to record the aftershocks of the 2007 event, was used to determine two-dimensional (2-D) and three-dimensional (3-D) velocity models of the Mentawai segment. The seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin. The downgoing slab is clearly distinguished by a dipping region of high Vp (8.0 km/s), which can be a traced to similar to 50 km depth, with an increased Vp/Vs ratio (1.75 to 1.90) beneath the islands and the western side of the forearc basin, suggesting hydrated oceanic crust. Above the slab, a shallow continental Moho of less than 30 km depth can be inferred, suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge. The outer arc islands are characterized by low Vp (4.5-5.8 km/s) and high Vp/Vs (greater than 2.0), suggesting that they consist of fluid saturated sediments. The very low rigidity of the outer forearc contributed to the slow rupture of the M-w 7.7 Mentawai tsunami earthquake on 25 October 2010. Y1 - 2012 U6 - https://doi.org/10.1029/2011JB008469 SN - 2169-9313 SN - 2169-9356 VL - 117 IS - 3 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Lange, Dietrich A1 - Bedford, J. R. A1 - Moreno, M. A1 - Tilmann, F. A1 - Báez, Juan Carlos A1 - Bevis, M. A1 - Krüger, Frank T1 - Comparison of postseismic afterslip models with aftershock seismicity for three subduction-zone earthquakes: Nias 2005, Maule 2010 and Tohoku 2011 JF - Geophysical journal international N2 - We focus on the relation between seismic and total postseismic afterslip following the Maule M-w 8.8 earthquake on 2010 February 27 in central Chile. First, we calculate the cumulative slip released by aftershock seismicity. We do this by summing up the aftershock regions and slip estimated from scaling relations. Comparing the cumulative seismic slip with afterslip modelswe showthat seismic slip of individual aftershocks exceeds locally the inverted afterslip model from geodetic constraints. As the afterslip model implicitly contains the displacements from the aftershocks, this reflects the tendency of afterslip models to smear out the actual slip pattern. However, it also suggests that locally slip for a number of the larger aftershocks exceeds the aseismic slip in spite of the fact that the total equivalent moment of the afterslip exceeds the cumulative moment of aftershocks by a large factor. This effect, seen weakly for the Maule 2010 and also for the Tohoku 2011 earthquake, can be explained by taking into account the uncertainties of the seismicity and afterslip models. In spite of uncertainties, the hypocentral region of the Nias 2005 earthquake is suggested to release a large fraction of moment almost purely seismically. Therefore, these aftershocks are not driven solely by the afterslip but instead their slip areas have probably been stressed by interseismic loading and the mainshock rupture. In a second step, we divide the megathrust of the Maule 2010 rupture into discrete cells and count the number of aftershocks that occur within 50 km of the centre of each cell as a function of time. We then compare this number to a time-dependent afterslip model by defining the 'afterslip to aftershock ratio' (ASAR) for each cell as the slope of the best fitting line when the afterslip at time t is plotted against aftershock count. Although we find a linear relation between afterslip and aftershocks for most cells, there is significant variability in ASAR in both the downdip and along-strike directions of the megathrust. We compare the spatial distribution of ASAR with the spatial distribution of seismic coupling, coseismic slip and Bouguer gravity anomaly, and in each case we find no significant correlation. KW - Creep and deformation KW - Earthquake dynamics KW - Seismicity and tectonics KW - Continental margins: convergent Y1 - 2014 U6 - https://doi.org/10.1093/gji/ggu292 SN - 0956-540X SN - 1365-246X VL - 199 IS - 2 SP - 784 EP - 799 PB - Oxford Univ. Press CY - Oxford ER -