Shear wave splitting in the Alpine region
Authors: Hein Gerrit , Kolínský Petr , Bianchi Irene , Bokelmann Götz ,   AlpArray Working Group, Hetényi György , Abreu Rafael , Allegretti Ivo , Apoloner Maria-Theresia , Aubert Coralie , Besançon Simon , Bés de Berc Maxime , Bokelmann Götz , Brunel Didier , Capello Marco , Čarman Martina , Cavaliere Adriano , Chéze Jérôme , Chiarabba Claudio , Clinton John , Cougoulat Glenn , C. Crawford Wayne , Cristiano Luigia , Czifra Tibor , D’Alema Ezio , Danesi Stefania , Daniel Romuald , Dannowski Anke , Dasović Iva , Deschamps Anne , Dessa Jean-Xavier , Doubre Cécile , Egdorf Sven , Fiket Tomislav , Fischer Kasper , Friederich Wolfgang , Fuchs Florian , Funke Sigward , Giardini Domenico , Govoni Aladino , Gráczer Zoltán , Gröschl Gidera , Heimers Stefan , Heit Ben , Herak Davorka , Herak Marijan , Huber Johann , Jarić Dejan , Jedlička Petr , Jia Yan , Jund Hélène , Kissling Edi , Klingen Stefan , Klotz Bernhard , Kolínský Petr , Kopp Heidrun , Korn Michael , Kotek Josef , Kühne Lothar , Kuk Krešo , Lange Dietrich , Loos Jürgen , Lovati Sara , Malengros Deny , Margheriti Lucia , Maron Christophe , Martin Xavier , Massa Marco , Mazzarini Francesco , Meier Thomas , Métral Laurent , Molinari Irene , Moretti Milena , Nardi Anna , Pahor Jurij , Paul Anne , Péquegnat Catherine , Petersen Daniel , Pesaresi Damiano , Piccinini Davide , Piromallo Claudia , Plenefisch Thomas , Plomerová Jaroslava , Pondrelli Silvia , Prevolnik Snježan , Racine Roman , Régnier Marc , Reiss Miriam , Ritter Joachim , Rümpker Georg , Salimbeni Simone , Santulin Marco , Scherer Werner , Schippkus Sven , Schulte-Kortnack Detlef , Šipka Vesna , Solarino Stefano , Spallarossa Daniele , Spieker Kathrin , Stipčević Josip , Strollo Angelo , Süle Bálint , Szanyi Gyöngyvér , Szűcs Eszter , Thomas Christine , Thorwart Martin , Tilmann Frederik , Ueding Stefan , Vallocchia Massimiliano , Vecsey Luděk , Voigt René , Wassermann Joachim , Wéber Zoltán , Weidle Christian , Wesztergom Viktor , Weyland Gauthier , Wiemer Stefan , Wolf Felix , Wolyniec David , Zieke Thomas , Živčić Mladen , Žlebčíková Helena 
Published: August 2021

To constrain seismic anisotropy under and around the Alps in Europe, we study SKS shear wave splitting from the region densely covered by the AlpArray seismic network. We apply a technique based on measuring the splitting intensity, constraining well both the fast orientation and the splitting delay. Four years of teleseismic earthquake data were processed, from 723 temporary and permanent broad-band stations of the AlpArray deployment including ocean-bottom seismometers, providing a spatial coverage that is unprecedented. The technique is applied automatically (without human intervention), and it thus provides a reproducible image of anisotropic structure in and around the Alpine region. As in earlier studies, we observe a coherent rotation of fast axes in the western part of the Alpine chain, and a region of homogeneous fast orientation in the Central Alps. The spatial variation of splitting delay times is particularly interesting though. On one hand, there is a clear positive correlation with Alpine topography, suggesting that part of the seismic anisotropy (deformation) is caused by the Alpine orogeny. On the other hand, anisotropic strength around the mountain chain shows a distinct contrast between the Western and Eastern Alps. This difference is best explained by the more active mantle flow around the Western Alps. The new observational constraints, especially the splitting delay, provide new information on Alpine geodynamics.