{"id":107,"date":"2017-07-18T15:15:30","date_gmt":"2017-07-18T15:15:30","guid":{"rendered":"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/?page_id=107"},"modified":"2025-03-07T19:06:31","modified_gmt":"2025-03-07T19:06:31","slug":"main-research-interests","status":"publish","type":"page","link":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/main-research-interests\/","title":{"rendered":"Main research interests"},"content":{"rendered":"<h2 style=\"text-align: left;\">My main fields of expertise are\u00a0<strong>Structural Geology and Tectonics<\/strong>.<\/h2>\n<h3>During my PhD &#8230;<img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-396\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/thesis_1.png\" alt=\"\" width=\"1066\" height=\"459\" \/><\/h3>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-473\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Snow_ball_1.png\" alt=\"\" width=\"928\" height=\"272\" \/><\/p>\n<p>&#8230; I&#8217;ve studied the <strong>Variscan orogen in SW Iberia<\/strong>, specifically the late Palaeozoic tectonic inversion of the Rheic (passive) continental margin, which is thought to have implied <strong>subduction and obduction along the so-called Ossa Morena Zone (OMZ)<\/strong> meridional domains (presently outcropping in SW Portugal), eventually leading to continental collision (SW Iberian Variscan orogen).\u00a0My work involved <strong>mapping of high grade gneiss terranes, and the study of HP exhumed rocks<\/strong>, coupled with <strong>analogue modelling of sheath folds<\/strong>. Here are the links for <a href=\"https:\/\/ulisboa-my.sharepoint.com\/:b:\/g\/personal\/frosas_fc_ul_pt\/EcDddFLiZWpPmueBtZkrFxIBzEb3wtSrOYI28nkWx-T2fg?e=HyANTQ\">my thesis (in Portuguese)<\/a> and to the 3 papers related to my PhD:<\/p>\n<ul>\n<li>Sheath folds #1 &#8211; <a href=\"http:\/\/memoirs.gsapubs.org\/content\/193\/101.full.pdf+html\">Has Ramberg AGU memoir paper<\/a><\/li>\n<li>Sheath folds#2 &#8211; <a href=\"http:\/\/dx.doi.org\/10.1016\/S0191-8141%2801%2900046-3\">Structural Geology paper<\/a><\/li>\n<li>Varican orogen in SW Iberia &#8211; <a href=\"https:\/\/doi.org\/10.1029\/2008TC002333\">Tectonics paper<\/a><\/li>\n<\/ul>\n<figure id=\"attachment_472\" aria-describedby=\"caption-attachment-472\" style=\"width: 855px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-472 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/SF_1.png\" alt=\"Sheet folds\" width=\"855\" height=\"299\" \/><figcaption id=\"caption-attachment-472\" class=\"wp-caption-text\">Eye and mushroom sheath fold patterns obtained from orthogonal cross sections of analogue models of sheath folds, formed from non-cylindrical geometrical anisotropies under non-coaxial shear deformation (pink and transparent PDMS silicone). Details here: https:\/\/doi.org\/10.1130\/0-8137-1193-2.101<\/figcaption><\/figure>\n<figure id=\"attachment_471\" aria-describedby=\"caption-attachment-471\" style=\"width: 771px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-471 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/SF_2.png\" alt=\"Syn shear rotated rigid inclusions and quarter structures sheath folds\" width=\"771\" height=\"222\" \/><figcaption id=\"caption-attachment-471\" class=\"wp-caption-text\">Quarter structures sheath folds formed due to the syn-shear, top to the left, rotation of an inequidimensional rigid body (black). Rigid body rotation perturbs the flow around it, creating a monoclinic pattern (symmetry) of sheath fold distribution around opposite quarters of the rigid body, which can be used to determine the prevailing bulk shear sense. Details here: https:\/\/doi.org\/10.1016\/S0191-8141(01)00046-3<\/figcaption><\/figure>\n<h3>More recently I have also worked on &#8230;<\/h3>\n<figure id=\"attachment_464\" aria-describedby=\"caption-attachment-464\" style=\"width: 578px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-464 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Corner_zone_1.png\" alt=\"Gulf of Cadiz thrust-wrench tectonic interference\" width=\"578\" height=\"404\" \/><figcaption id=\"caption-attachment-464\" class=\"wp-caption-text\">Map of the corner zone thrust-wrench tectonic interference between major active tectonic structures in the Horseshoe Abyssal Plain, Gulf of Cadiz, region. Details here: https:\/\/doi.org\/10.1016\/j.tecto.2012.04.013<\/figcaption><\/figure>\n<p>&#8230; The (neo)<strong>tectonics<\/strong> of the offshore SW Iberia, along the\u00a0<strong>Eurasia-Nubia plate boundary (NE Atlantic)<\/strong>, more specifically, on trying to<strong> unravel the seismogenic and tsunamigenic sources<\/strong> (i.e., main active tectonic structures) responsible for the important historical and instrumental seismicity in this area, in which the<strong> 1755 great Lisbon Earthquake\u00a0<\/strong>occurred. Within this research line I&#8217;ve pursued the following main approaches:<\/p>\n<ul>\n<li>\n<h4><strong>Geodynamic modelling of active transcurrent (strike-slip) fault systems:<\/strong><\/h4>\n<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-407\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Lineaments.png\" alt=\"\" width=\"818\" height=\"331\" \/><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-408\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/lineaments_2.png\" alt=\"\" width=\"818\" height=\"153\" \/>Analogue modelling and tectonic interpretation of <strong>200km long bathymetric lineaments<\/strong> in the Gulf of Cadiz sea floor as <strong>major active strike-slip faults<\/strong> (the so called SWIM faults) &#8211; <a href=\"https:\/\/doi.org\/10.1016\/j.margeo.2008.08.002\">Marine Geology paper<\/a>.<\/p>\n<ul>\n<li>\n<h4><strong>Geodynamic modelling of thrust-wrench fault interference:<\/strong><\/h4>\n<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-402\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Num_interference_1.png\" alt=\"\" width=\"801\" height=\"407\" \/>a) Coupled analogue and numerical modelling of the active <strong>fault interference<\/strong> <strong>between major active strike-slip faults and thrusts<\/strong> in the Gulf of Cadiz &#8211; <a href=\"http:\/\/dx.doi.org\/10.1016\/j.tecto.2012.04.013\">Tectonophysics paper<\/a>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-427\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/interference_new.png\" alt=\"\" width=\"1231\" height=\"579\" \/>b) Analogue modelling of <strong>general (different angle) interference between active thrust and strike-slip faults<\/strong> &#8211; <a href=\"https:\/\/doi.org\/10.1016\/j.jsg.2015.03.005\">Journal of Structural Geology paper<\/a>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-477\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Thrust_wrench_fault_interference.png\" alt=\"\" width=\"823\" height=\"416\" \/>c) Seismogenic<strong> potential of active fault interference<\/strong> in the Gulf of Cadiz (offshore SW Iberia, NE Atlantic) <strong>for the generation of high and very high magnitude earthquakes <\/strong>in the region, <strong>including the 1755 Great Lisbon Earthquake<\/strong>. \u00a0&#8211;\u00a0<a href=\"https:\/\/doi.org\/10.1002\/9781119054146.ch9\">Book chapter, AGU, Geophysical Monograph Series, Plate boundaries and natural hazards<\/a>.<\/p>\n<ul>\n<li>\n<h4><strong>Subduction initiation along the Wester Iberian Margin (WIM)<\/strong><\/h4>\n<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-419\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Geology1.png\" alt=\"\" width=\"1279\" height=\"681\" \/>Is a <strong>new subduction zone being formed along the WIM<\/strong>, transforming the Atlantic passive margin into an active one? Is this <strong>being induced<\/strong> by the previous, waning(?), <strong>Gibraltar subduction zone<\/strong> in the Gulf of Cadiz? Work led by former PhD student <a href=\"https:\/\/joaocduarte.weebly.com\">J. Duarte<\/a>. &#8211; <a href=\"https:\/\/doi.org\/10.1130\/G34100.1\">Geology paper<\/a>.<\/p>\n<h2>My present research &#8230;<\/h2>\n<p>&#8230; is mainly focused on using <b>analogue and numerical geodynamic modelling <\/b>to understand the dynamics of different\u00a0<b>tectonic\/geodynamic problems at different scales<\/b>, such as:<\/p>\n<ul>\n<li>\n<h3><strong>Subduction initiation:<\/strong><\/h3>\n<\/li>\n<\/ul>\n<p>1. Polarity-reversal <strong>subduction initiation (2D)<\/strong><\/p>\n<p><iframe loading=\"lazy\" title=\"YouTube video player\" src=\"https:\/\/www.youtube.com\/embed\/XYO6i0if8zM\" width=\"560\" height=\"315\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p>A<strong> buoyant oceanic plateau atop the original subducting plate<\/strong> arrives to the subduction trench, <strong>obstructing it (resisting subduction), and triggering a new subduction zone in the opposite direction<\/strong> (opposite polarity). Note that the model<strong> is<\/strong> <strong>NOT forced externally <\/strong>by any imposed velocity BCs, but rather, it is <strong>driven exclusively by the force equilibrium between the negative buoyancy of the subducting slab, and the viscous resisting forces in the mantle<\/strong>. This work was led by former PhD student <a href=\"http:\/\/idl.campus.ciencias.ulisboa.pt\/idlmember\/jaime-almeida\/\">Jaime Almeida<\/a> &#8211; <a href=\"https:\/\/doi.org\/10.1016\/j.epsl.2021.117195\"><em>EPSL<\/em>\u00a0paper<\/a>.<\/p>\n<figure id=\"attachment_448\" aria-describedby=\"caption-attachment-448\" style=\"width: 2366px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-448 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Destaque_1.png\" alt=\"Polarity reversal subduction initiation\" width=\"2366\" height=\"773\" \/><figcaption id=\"caption-attachment-448\" class=\"wp-caption-text\">2D polarity-reversal subduction initiation: the original left-dipping subduction comes to an alt due to the obstruction of the subduction trench by a buoyant plateau, and a new right dipping subduction is initiated.<\/figcaption><\/figure>\n<p>2. Polarity-reversal <strong>subduction initiation (3D)<\/strong><\/p>\n<p><iframe loading=\"lazy\" title=\"YouTube video player\" src=\"https:\/\/www.youtube.com\/embed\/58uPRTbI8uM\" width=\"560\" height=\"315\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p>The video above (be patient in takes a few seconds to start) shows\u00a0<strong>polarity reversal subduction initiation<\/strong> occurring, also in a dynamic self consistent model (i.e., in the absence of any external forcing), but now at <strong>3D<\/strong>. Note that the contribution of the <strong>negative buoyancy of the slab in the 3rd dimension is now taken into account<\/strong>, as well as the feed-back effect of the flow in the mantle. This work was led by former PhD student <a href=\"http:\/\/idl.campus.ciencias.ulisboa.pt\/idlmember\/jaime-almeida\/\">Jaime Almeida<\/a> &#8211; \u00a0<a href=\"https:\/\/doi.org\/10.1038\/s43247-022-00380-2\"><i>Commun Earth Environ<\/i> paper<\/a>.<\/p>\n<figure id=\"attachment_458\" aria-describedby=\"caption-attachment-458\" style=\"width: 2181px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-458 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/PRSI_3D.png\" alt=\"3D numerical model of polarity reversal subduction initiation\" width=\"2181\" height=\"1131\" \/><figcaption id=\"caption-attachment-458\" class=\"wp-caption-text\">Polarity reversal subduction initiation at 3D (top free-surface BC). These set of models allowed us to explore parameters in the 3rd dimension, namely the slab-pull along that direction and the influence of the width of the buoyant plateau.<\/figcaption><\/figure>\n<ul>\n<li>\n<h3><strong>Continental rifting:<\/strong><\/h3>\n<\/li>\n<\/ul>\n<p>1. Numerical modelling of crustal continental rift, to understand the influence of differently assumed crustal rheological configurations on the <strong>development of double grabens during early-rift evolution<\/strong>.<\/p>\n<p><iframe loading=\"lazy\" title=\"YouTube video player\" src=\"https:\/\/www.youtube.com\/embed\/gcZ128Xc7DA\" width=\"560\" height=\"315\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p>Investigated variables also included<strong> the existence vs. absence of crustal weak seeds<\/strong> (crustal weak anisotropies such as pre-existent faults or magmatic chambers), <strong>in different numbers and at different distances from each other<\/strong>. This work was led by former PhD students <a href=\"https:\/\/www.researchgate.net\/profile\/Magda-Oliveira\">Magda Oliveira<\/a> and <a href=\"http:\/\/idl.campus.ciencias.ulisboa.pt\/idlmember\/afonso-gomes\/\">Afonso Gomes<\/a> &#8211; <a href=\"https:\/\/doi.org\/10.1016\/j.tecto.2022.229281\">Tectonophysics paper<\/a><\/p>\n<figure id=\"attachment_444\" aria-describedby=\"caption-attachment-444\" style=\"width: 755px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-444 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Magda_1.png\" alt=\"Double graben formation during initial rifting (two week seeds at the base of the upper crust)\" width=\"755\" height=\"669\" \/><figcaption id=\"caption-attachment-444\" class=\"wp-caption-text\">Deformation (extension) is initially nucleated atop the two seeds (double graben formation), but eventually one of the main grabbers is abandoned and strain is fully localised in only one of these structures.<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<p>2. Analogue modelling of continental crust extension, focusing on the <strong>investigation of crustal rheology on the type of fault distribution pattern<\/strong> (degree of fault delocalisation) affecting the brittle upper crust as a result.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-435 alignleft\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Ruth1.png\" alt=\"\" width=\"474\" height=\"304\" \/>a) These Analogue modelling experiments were conceived to investigate the <strong>influence of the thickness of a weak (viscous) middle crust \u00a0layer, on the resulting delocalisation fault distribution pattern<\/strong> along the overlying brittle layer (elastic upper crust).\u00a0This work was led by former MSc student \u00a0<a href=\"https:\/\/www.researchgate.net\/profile\/Ruth-Keppler-2\">Ruth Keppler<\/a> &#8211; <a href=\"https:\/\/doi.org\/10.1016\/j.tecto.2013.10.001\">Tectonophysics paper<\/a>.<\/p>\n<ul>\n<li>\n<h3><strong>Thrusting<\/strong><\/h3>\n<\/li>\n<\/ul>\n<p>Analogue modelling study of <strong>passive deformation of a weak hanging wall<\/strong> (allochthonous unit) <strong>while its being emplaced above a rigid footwall with different thrust ramp geometries <\/strong>(flat-ramp-flat vs.\u00a0concave-convex geometry):<\/p>\n<figure id=\"attachment_513\" aria-describedby=\"caption-attachment-513\" style=\"width: 825px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-513 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/thrust_ramps.png\" alt=\"Thrust ramps\" width=\"825\" height=\"633\" \/><figcaption id=\"caption-attachment-513\" class=\"wp-caption-text\">Analogue modelling of thrust systems: Passive vs. active hanging wall strain accommodation and sharp vs. smooth fault-ramp geometries<\/figcaption><\/figure>\n<p>Details of this work can be found in this <a href=\"https:\/\/doi.org\/10.1016\/j.jsg.2017.05.002\">Journal of Structural Geology paper<\/a><\/p>\n<ul>\n<li>\n<h3><strong>Strike-slip faulting across\u00a0<\/strong><b>morph-rheological obstacles<\/b><\/h3>\n<\/li>\n<\/ul>\n<p>Analogue modelling of the tectonic interference between active strike-slip faults systems and morph-rheological barriers (obstacles):<\/p>\n<p><iframe loading=\"lazy\" title=\"YouTube video player\" src=\"https:\/\/www.youtube.com\/embed\/GtN_y_PsbQk\" width=\"560\" height=\"315\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p>Video depicts a top view of this interference in models striped of their cover (top) sand layer: while <strong>all strike-slip Riedel structures develop and coalesce in the sand, the black silicone body changes from circular to elliptic<\/strong>, with increasing eccentricity and with its shear plane rotating to the (horizontal) shear plane.<\/p>\n<figure id=\"attachment_519\" aria-describedby=\"caption-attachment-519\" style=\"width: 825px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-519 size-full\" src=\"http:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/wp-content\/uploads\/2022\/11\/Afonso_2.png\" alt=\"\" width=\"825\" height=\"538\" \/><figcaption id=\"caption-attachment-519\" class=\"wp-caption-text\">Analogue modelling of the interference between an active strike-slip system (dextral) and a viscous cross cutting obstacle (black silicone body). Orthogonal cut obtained from the model final stage.<\/figcaption><\/figure>\n<p>Work led by former MSc student <a href=\"http:\/\/idl.campus.ciencias.ulisboa.pt\/idlmember\/afonso-gomes\/\">Afonso Gomes<\/a> &#8211; <a href=\"https:\/\/doi.org\/10.1016\/j.jsg.2019.06.004\">see JSG paper for details<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>My main fields of expertise are\u00a0Structural Geology and Tectonics. During my PhD &#8230; &#8230; I&#8217;ve studied the Variscan orogen in SW Iberia, specifically the late Palaeozoic tectonic inversion of the Rheic (passive) continental margin, which is thought to have implied subduction and obduction along the so-called Ossa Morena Zone (OMZ) meridional domains (presently outcropping in &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/main-research-interests\/\" class=\"more-link\">Continuar a ler <span class=\"screen-reader-text\">&#8220;Main research interests&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-107","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/pages\/107","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/comments?post=107"}],"version-history":[{"count":121,"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/pages\/107\/revisions"}],"predecessor-version":[{"id":720,"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/pages\/107\/revisions\/720"}],"wp:attachment":[{"href":"https:\/\/webpages.ciencias.ulisboa.pt\/~frosas\/index.php\/wp-json\/wp\/v2\/media?parent=107"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}