AGU 2022 practice
2022-12-07 12:00 - 13:00 (Europe/Oslo)
Thomas Theunissen – Oblique continental rifting. Insights from 3-D forward geodynamic modelling coupled with surface processes and application to the Equatorial passive margins formation.
Sebastian Wolf – How high do mountains grow? quantifying growth and decay of topography in collision orogens
Björn Johan Emil Burr Nyberg – Global Scale Analysis on the Geomorphology of Rivers and Channel Belts

Thomas Theunissen – Oblique continental rifting. Insights from 3-D forward geodynamic modelling coupled with surface processes and application to the Equatorial passive margins formation.
Plate divergence (continental rifting) is often oblique to the rift axis or plate boundary, comprising many active rifts and mature rifted margins on Earth. Recent findings from field-based studies, plate reconstructions and numerical and analog models suggest that rift obliquity plays a critical role in rift evolution and imparts fundamental controls on the eventual architecture of mid-ocean ridges and mature rifted margins. These studies show the importance of vertical strike-slip and transform structures in the oblique extension process but also reveal that the initiation of syn-rift vertical strike-slip motion over long distances requires inherited weaknesses. As a typical example the Southern part of the Equatorial passive rifted conjugate margins exhibit segments with different tectonics and subsidence histories alternating with transform segment with different lengths and orientation. We aim in this study 1) to evaluate the role of the inheritance (obliquity, geometry of weaknesses) in controlling the pattern of faulting (type of fault, direction of propagation, and linkage), and 2) to evaluate the feedback between tectonics and surface processes in this context to understand consequences on landscape evolution. For this purpose, we use most recent advances in 3-D forward geodynamic modeling coupled with surface processes. Preliminary results confirm the importance of inheritance in shaping the continental rift by controlling fault propagation leading to oblique segments with variable tectonics and subsidence history and show some unexpected feedbacks between tectonics and surface processes. These results compare well to the Equatorial system and provide important insight on the causes that might explain timing and amplitude of vertical motions and related sediment flux.
Björn Nyberg – Global Scale Analysis on the Geomorphology of Rivers and Channel Belts
Rivers are fundamental geomorphic features on the Earth’s surface and have an important role in controlling human habitat, climate, ecosystems, and the hydrological cycle. However, only recently has the surface area of rivers globally been quantified, and there remains a significant knowledge gap in understanding the distribution of river types, the extent of channel belt deposits and their morphology. Yet it is these factors that ultimately control the behavior of river systems and the ecosystems and human livelihoods that depend on those rivers. Here we develop a novel machine learning method to recognize the patterns of different river channels and their deposits to classify their morphology. Our results quantify, for the first time, that the global observable extent of river channel belts covers an area of 30.5 x 105 km2, which equates to roughly the known size of lakes or 7 times larger than the extent of river channels. Of those channel belts, nearly 77% of the surface area are classified as meandering with the remainder defined by a more braided morphology. Furthermore, we quantify the hydrological, physio-climatic and tectonic controls governing the geomorphology of rivers globally. It is hoped that the new Global River Morphology (GRM) map and database may provide new insights into predicting the intensity and behavior of future floods, improve analysis of biogeochemical cycles and aid in water resource management
Sebastian Wolf – How high do mountains grow – quantifying growth and decay of topography in collisional orogens
How does a collisional mountain belt grow and decay? It is widely recognized that crustal thickening creates topography, while river incision counteracts orogenic growth and leads to topographic decay, thus providing a link between climate, surface processes and tectonics. However, it remains uncertain whether surface processes or lithospheric strength control mountain belt height, width, and longevity, reconciling high erosion rates observed for instance in Taiwan and New Zealand, low erosion rates in the Tibetan and Andean plateaus, and long-term survival of mountain belts for several 100s of million years. Here we use a tight coupling between a landscape evolution model (FastScape) and a thermo-mechanically coupled mantle-scale tectonic model (Fantom) to investigate mountain belt growth and decay. Using several end-member models and introducing the new non-dimensional Beaumont number, Bm, we quantify how surface processes and tectonics control mountain growth and define three end-member types of growing orogens: Type 1, non-steady state, strength controlled (Bm > 0.5); Type 2, flux steady state, strength controlled (Bm ≈ 0.4−0.5); and Type 3, flux steady state, erosion controlled (Bm < 0.4). Bm can be assessed without complex measurements or assumptions, but simply by knowing a mountain belt’s convergence rate, height, width, first order shortening distribution, and widening rate. Applying our results to several orogens on Earth indicates that tectonics dominate in the Central Andes and Himalaya-Tibet (both Type 1), efficient surface processes balance high convergence rates in Taiwan (Type 2), and surface processes dominate in the Southern Alps of New Zealand (Type 3). Quantifying orogenic decay, we find that removal of topography is primarily determined by erosional efficiency and can be subdivided into two phases with variable isostatic rebound characteristics and associated timescales: First short-wavelength relief is removed within a few Myr, followed by removal of long-wavelength topography and effectively local isostatic rebound. Our results provide a simple unifying framework quantifying how surface processes and tectonics control the shape, height, and longevity of mountain belts on Earth.

Ingrid Kristine Jacobsen & Omar Yesid Duran Triana
2023-01-11 12:00 - 13:00
Ingrid Kristine Jacobsen (and here)– abstract:

Exploitation of energy from enhanced geothermal systems is performed by injecting fluid at high pressure into the reservoir such that faults are deliberately opened. The fault opening causes enhancement of the fluid flow, which is favorable for exploitation of the geothermal energy, but also fault slip, which may be of the unstable kind that results in induced seismicity.
In this talk I will first present a mathematical model for fault deformation in a mixed-dimensional setting. Then I will move on to talk about the concepts behind the rate and state friction (RSF) models which are widely used in simulations regarding seismicity. Briefly explained, RSF models consider the coefficient of friction to be dependent on both slip rate and the state of the contacting rock surfaces, and parameters appearing in its model equations can tell us about whether fault slip will be unstable (seismic) or stable (aseismic).

Omar Yesid Duran Triana (and here)- abstract:
This research was inspired and intended as an extension to the mixed-dimensional poromechanical models for fractured media presented in [1]. There the classical continuum mechanics is considered in the context of finite and infinitesimal strain. We addressed fracture mechanics from a different perspective by considering the linear theory of the Cosserat (micropolar, asymmetric) continuum. We considered an conforming-H1 method for the resulting set equations. Extra regularity can be achieved on the asymmetric component of the stress tensor and fracture tractions through the angular momentum balance defined on surfaces. We addressed the second-order formulation and present numerical results for the adopted model.
[1] W.-M. Boon and J.-M. Nordbotten. Mixed-dimensional poromechanical models of fractured porous media. Acta Mech (2022).

Melanie Kling
2023-01-18 12:00 - 13:00
Response of a clastic source-to-sink system to extreme environmental perturbations: the Permian-Triassic transition on Finnmark Platform, Barents Sea
Melanie Kling
The eruption of the Siberian Traps at the Permian-Triassic transition significantly affected depositional environments world-wide. Known consequences are (I) extreme global warming, (II) increased soil-erosion, decreasing chemical weathering and aridification on the continents, (III) oceanic stagnation and acidification, and (IV) the most severe mass extinction on Earth. In the Southwestern Barents Sea, the record across the Permian transition is continuous at a cored site located close to the basin margin, making it possible to study the response of a relatively proximal source-to-sink system in terms of petrography, provenance, and sedimentary environments. The record consists of Upper Permian carbonates developed as an oxygenated carbonate platform, overlain by transitional dys- or anoxic, organic-rich shales and a Lower Triassic prograding siliciclastic turbidite-prodelta-delta system.
In this project we use these deposits to reconstruct the sediment source area and changes within the catchment area across the Permian-Triassic transition. From a dataset of >50 2D seismic lines and sampled sandstones from ~160 m stratigraphic cores, we have already found that the sediment supply rate increased by more than 100-fold, which vastly exceeds the world-wide trend of sediment supply increase across the Permian-Triassic transition (6–7-fold). This has led to several models that may explain the observed evolution, but in order to distinguish between these models, mudstone provenance and weathering proxies must also be investigated. Herein we focus on the Neodymium and Hafnium isotopic composition in the mudstones, and thus present insights into weathering processes. This will allow us to investigate the climatic component in the catchment across the transition. Our preliminary results show that the catchment in the Late Permian supplied mudstones with extreme (much more than observed in modern deposits) chemical weathering and a stable provenance from a small, nearshore catchment. Broadly coincident with the Permian Triassic Transition, mudstones show a provenance change consistent with increase in catchment area and a strong decrease in chemical weathering. This indicates that the increase in sediment supply from at the Permian-Triassic transition was not caused by sudden flushing of onshore weathered material stored in catchments during the Permian, nor can it be caused by increase in chemical weathering because of climate change. It appears that the observed changes are mainly a result of tectonic uplift and tilting of Northern Fennoscandia possibly due to onset of a new rifting episode in the Norwegian-Greenland Sea. The coincidence of this strong response to the Permian-Triassic transition could perhaps indicate that adjustments of the catchment to the new topographic setting was helped by the climate change.

Martin Kjenes
2023-01-25 12:00 - 13:00
Martin Kjenes
coming soon…

Albina Gilmullina
2023-02-01 00:00 - 13:00
Albina Gilmullina
coming soon…

Helene Stemland
2023-02-08 00:00 - 13:00
Helene Stemland
coming soon…

James Opemipo Olomo
2023-02-15 12:00 - 13:00
Along strike variability of structural style and evolution of the South Viking Graben and western flank of the Utsira High
James Opemipo Olomo

Mads Jelby
2023-02-22 12:00 - 13:00
Far from home: Facies architecture of distal delta wedges across a wide ramp (Lower Cretaceous, Svalbard)
Mads E. Jelby

Anne Imig
2023-03-01 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Assessing managed aquifer recharge as a sustainable measure for groundwater management – An application for Grand Bahama
Anne Imig
A large storm surge caused by Hurricane Dorian in 2019 resulted in saltwater intrusion into the aquifers of Grand Bahama Island. This caused 40% of the island’s water supply to become brackish with no or slow recovery to date. Managed aquifer recharge (MAR) is investigated as a nature-based solutions to mitigate the impacts of Hurricane Dorian. First, a technical assessment of MAR investigates (hydro-) geological aspects. As a result, potential locations for a MAR scheme are proposed. Further, a financial and an extended cost-benefit analysis (CBA) integrating ecosystem services (ES) assessments are conducted for proposed MAR measures. Based on the current data availability, results indicate that the MAR scheme is technically feasible. However, it will not be able to provide the water demand and is not favorable from a financial perspective in comparison to a desalinization plant. The results of this study proofs the technical feasibility and the added value of restoring the groundwater ecosystem on Grand Bahama, but also highlight that high costs are connected with it. Due to the high costs the added value should be reevaluated and further data should be collected to support the findings.

Enry Horas Sihombing
2023-03-08 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Geomorphology of normal fault footwalls and fault scarps: Greater Tampen Spur Area, northern North Sea
Enry Horas Sihombing
Late Jurassic rifting in the Greater Tampen Spur area created a network of major normal faults, the footwall crests and fault scarps of which show major variations in their geomorphology. In this study we characterise this variable footwall geomorphology using a ~3700 km2 3D PSDM seismic volume and several key wells from the Snorre and Visund fault blocks. Our objectives are to: (1) document the different geomorphic characteristics of major footwall blocks; (2) illustrate the variable geomorphology of fault-controlled scarps; 3) define the syn- and early post-rift depositional systems in the immediate hanging walls of major normal faults and their relationships to the geomorphology of the adjacent footwalls; and 4) understand the tectonic, stratigraphic and surface processes responsible for developing varied footwall and fault scarp geomorphology. Visund and Snorre footwall blocks exhibits differing styles of footwall crest shape and internal morphology. The Snorre fault footwall has a broad, 10-14 km wide and 60 km long, gently west-dipping plateau whereas the Visund fault footwall has a curved convex-up, east-dipping, nearly 50 km long and 6-8 km wide crest in cross section which gives way to a westward facing dip-slope. The fault scarps associated with the Snorre, and Visund fault blocks host collapsed and rider blocks of different stages of maturity, mass wasting complexes and canyon systems. Rider blocks and fault scarp collapse structures are most common along the Snorre fault zone and are located at the point of maximum fault displacement (3-5 km throw). In areas of lower displacement, both fault blocks exhibit canyon systems along their southern extents, with canyons 1-2 km in width and <0.5 km deep. Canyons are consistently observed where the footwall and fault scarp host the Late Trassic Lunde Formation in the subcrop of the Base Cretaceous Unconformity (BCU). The variability of fault scarps may be controlled by interactions of mechanical strength of pre-rift stratigraphy and the tectonic setting and evolution. Along-strike and temporal variability in displacement along the fault segments would also produce differing uplift histories along, and between fault segments. Furthermore, strain migration towards the rift axis is interpreted to produce different depositional environments (a subaerially exposed Snorre footwall and largely subaqueous Visund footwall) during much of the Late Jurassic, which likely created different erosion potential and geomorphic responses between the two fault blocks. The study highlights the importance of integrating both local and regional tectono-sedimentary factors when characterising the highly variable character of fault scarp degradation.

Kui Xang
2023-03-15 12:15 - 13:00
Non-linear inverse scattering in anisotropic elastic media using a modified Born iterative method
Kui Xang
Estimating an accurate subsurface model of the Earth is crucial for identifying the locations of reservoirs. With the development of long offsets and wide azimuth seismic data acquisition, we can extract multiple anisotropic parameters from the recorded data to describe the right physical features of the Earth’s subsurface. Recently, we present an iterative non-linear inverse scattering algorithm for the reconstruction of the elastic parameters and mass density. To solve the non-linear forward scattering problem, we transform the elastodynamic wave equation into an integral equation, and then solve that integral equation by a fast-Fourier-transform-accelerated Krylov space method. For the non-linear inverse scattering problem, we approximate it to a series of linear approximations by using the Born approximation. Then, we use a modified Born iterative method to invert the model update at each linear approximation. The modified Born iterative method is based on the explicit computation of the Fréchet derivative. In our algorithm, the Fréchet derivative and its adjoint operators are presented in matrix-free manners so that we can also use the fast Fourier transform to reduce the computational cost and memory demand. We formulate the multi-parameter non-linear inverse scattering problem using a modified matrix-free Born iterative method. The application of synthetic data examples demonstrates its capability to produce accurate inversion results.

Dana Silerova
2023-03-22 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Long-lived (180 Myr) ductile flow within the Great Slave Lake shear zone
Dana Silerova
The Great Slave Lake shear zone (GSLsz) is a type example for deeply eroded continental transform boundaries located in the Northwest Territories, Canada. Formed during the oblique convergence of the Archean Rae and Slave cratons, the GSLsz has accommodated up to 700 km of dextral shear, however, the timing and duration of ductile deformation have not yet been directly constrained. New results of in situ U-Pb apatite and titanite geochronology from samples collected across the shear zone record a near-continuous history of ductile shear spanning ca. 1920–1740 Ma, with strain initially being accommodated along two coeval fault strands and later localizing along existing crustal structures during cooling and exhumation

Jokhongir Khayrullaev
2023-03-29 12:00 - 13:00
Exploring subsurface by means of a generalization of Dix’ classic time-to-depth mapping method
Jokhongir Khayrullaev
Primary goal of ongoing the research work is to develop new tools in compressional waves (P-waves) domain for exploring the subsurface by means of a generalization of Dix’ classic time-to-depth mapping method, where velocity estimation constitutes an inherent part. A fundamental idea behind the work is the generalized Dix method, recently published in de Hoop et al. 2014. As the name indicates, it represents a generalization of Dix’ classic method (Dix 1955) for interval velocity estimation and time-to-depth conversion, which has been a cornerstone in the conventional seismic data processing. Whereas the classic Dix method is based on an assumption of a 1-D subsurface, varying only in depth, the generalized method adopts the assumptions of 3-D seismic time migration. That means the subsurface properties may have a quite general variation with depth, while lateral variations are assumed to be weak or moderate.

Tony Doré
2023-03-30 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Continental-scale strike-slip faults and their influence on Atlantic and Arctic break-up
Tony Doré (EGI,Uni of Utah)
Abstract:
An idea that has wide currency in plate tectonics is that extending continental margins will undergo gradual stretching, including the exhumation of continental mantle, unless affected by an extraneous heat source, for example a mantle plume, forming a magma-rich margin. Such margins are typically more abrupt and characterized by seaward-dipping reflectors and underlying high-velocity intrusions. We propose an alternative, or additional mechanism for such margins involving the reactivation of continental transform or transcurrent faults, structures of lithospheric scale originally formed during continental assembly. In this concept. rapid development of abrupt margins results in significant lateral thermal gradients, triggering melt formation. The mechanism also explains the curious near-absence of pre-breakup extension at many such margins, and the frequently short-lived nature of the subaerial magmatic episode prior to the formation of normal oceanic crust – even at margins proposed to be under plume influence. These ideas are supported by lithospheric modelling, by examination of “leaky” transforms in the oceanic and continental domains, and by case-studies from the Arctic and North-Central Atlantic.
Bio:
Tony Doré held senior geoscience and leadership positions with ConocoPhillips and Equinor, and on retirement from Equinor joined the Energy and Geoscience Institute as Global Chief Scientist, based in London. His career involved a long period in Norway, where he formed strong links with universities such as Bergen, Oslo and Tromsø. This association continues with his current role as advisor to postdoctoral work in Bergen. He has worked, and published on, basins all over the world, with emphasis on NW Europe, Arctic and the Americas. Present interests include tectonic evolution of the Arctic, Gulf of Mexico, transform margins, cratonic basins and exploration risk analysis. Tony was recently appointed as Executive Editor of the diamond open access structural geology journal, Tektonika.

EGU practice talks
2023-04-19 12:00 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Thomas Theunissen
Oblique continental rifting. Insights from 3-D forward coupled geodynamic-surface process modelling and application to the Equatorial passive margins formation

Leonardo Pichel
Geodynamic modelling of salt-bearing rifted margins: from minibasin- to margin-scale salt tectonics across different margin types
The Inception and evolution of wide salt-bearing rifted margins – insights from numerical modelling and natural systems

Gang Lu
Three-field finite-element modelling of coupled two-phase flow for geological problems: Towards the zero-porosity limit

Melanie Kling
Weathering response of a clastic source-to-sink system to extreme environmental perturbations: the Permian-Triassic transition on Finnmark Platform, Barents Sea

Lucas Valore
Control of dynamic uplift on paleogeography and sediment volumes: insights from the East Shetland Platform in the Paleocene

Sebastian Wolf
The Beaumont number of mountain belts – quantifying the interaction between surface processes and tectonics during orogenesis

Mike Hudec
2023-04-28 12:15 - 13:00
Interaction between salt and mobile shale in the East Breaks foldbelt, Northwestern Gulf of Mexico
Mike Hudec
Bio:
The main focus of my research is salt tectonics, particularly kinematic models for evolution and growth of salt structures. This interest began upon my arrival at Exxon Production Research in 1989, when I was informed that I would be the company’s new expert on salt tectonics despite the fact that I was almost completely unfamiliar with the topic. The learning curve was quite steep at first, but as time passed I became progressively more enamored with salt deformation. After a 3-year stint teaching structural geology at Baylor University, I moved to Austin in 2000 to join the Applied Geodynamics Laboratory, an industry-funded research consortium studying salt tectonics. I have been codirector of the consortium since 2002.
My current research is focused on three topics. First, I am investigating the influence of basement structure and basement reactivation on salt tectonics, especially on passive margins in Brazil, West Africa, and the Gulf of Mexico. Second, I am interested in the emplacement and deformation of allochthonous salt sheets and canopies, mostly in the Gulf of Mexico. Finally, Martin Jackson and I are in the process of writing a textbook on salt tectonics and the seismic interpretation of salt structures.

Helene Meling Stemland
2023-05-03 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Passive seismic monitoring of an arctic glacier
Helene Meling Stemland
Widespread glacier loss is observed in the Arctic region, partly caused by rising surface temperatures. Calving, which is the mechanical break-off of ice at the glacier terminus, is important to monitor to estimate the potential sea level rise due to glacier mass loss, but is difficult due to the remote and seasonally dark locations of many glaciers. To overcome this challenge, the field of cryoseismology, where seismic waves from glacial environments are recorded and analyzed, is expanding. In this talk, I will describe the details of two seismic experiments we have conducted at a partly marine-terminating glacier on Svalbard. We placed seismic receivers on land and at the seabed in front of the glacier, and passively monitored the glacier for up to five weeks. We recorded seismic signals attributed to calving, fracturing/crevassing, and tectonic earthquakes. Here, I will talk about the challenges involved in the seismic campaigns, lessons learnt, and share some of the preliminary analysis of the data.

Matteo Ravasi
2023-05-04 14:15 - 15:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Seeing through the CO2 plume: joint-inversion segmentation of the Sleipner 4D dataset
Matteo Ravasi
4D seismic inversion is the leading method to monitor fluid flow dynamics in the subsurface, with applications ranging from enhanced oil recovery to subsurface CO2 storage. The process of inverting seismic data for reservoir properties is, however, a notoriously ill-posed inverse problem due to the band-limited and noisy nature of seismic data. This comes with additional challenges for 4D applications given inaccuracies in the repeatability of the time-lapse acquisition surveys.
If you want any further information on this talk or want to meet with Matteo, then get in touch with Isabelle Lecomte (Isabelle.Lecomte@uib.no).

Martin Muravchik
2023-05-10 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
AUV High-Resolution Bathymetry Of Axial-Transverse Drainage Interaction In The Structurally Controlled Subaqueous Channels In The Gulf Of Corinth, Corinth Rift, Greece
Martin Muravchik
New high-resolution (submeter) bathymetric data, acquired using an AUV Hugin 1000, from the Gulf of Corinth, Greece reveals unprecedent detail on the interaction between transverse and axial submarine channels in an active rift. The dataset presented was acquired using the EM2040 Multibeam Echosounder on the AUV at 300 and 400 kHz, navigating between 100 and 50 m above the seafloor. The surveyed area lies towards the western part of the Gulf of Corinth, offshore of the coastal towns of Aigio and Akrata. The area is characterized by the development of coarse-grained deltas sourced by north-flowing rivers draining the mountain ranges. The seafloor morphology shows the presence of active canyons, ca. 100 m deep, draining from the delta fronts towards north in water depths between 100 to 600 m, interacting with an axial trunk channel in water depths between 550 to 650 m, draining towards east, and which looses its expression in water depths between 700 and 800 m. These submarine channels show a strong structural control in both position and orientation by the normal faulting affecting the present-day Gulf of Corinth sea-floor. This survey includes the mapping of the three submarine tributaries derived from the Soulinous, Kerinitis and Vouraikos deltas and their link into the axial trunk channel. The survey shows the presence of large erosional scours in the axial channel, at the confluence with of some of the tributaries. This, together with the pervasive erosional features developed on the axial channel base and margins towards its exit onto the basin-floor, reveal the development of complex erosive flow patterns due to changes in the gradient of the sea-floor and the orientation of channel margins at the confluences between the tributaries and the axial channel.

Tena Belinić Topić
2023-05-11 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Exploring the lithospheric structure beneath the Dinarides using seismograms of teleseismic earthquakes
Tena Belinić Topić
The Dinarides are a mountain range located in southeastern Europe with significant tectonic activity and complicated geologic history shaped by the collision of the Adriatic microplate and the European mainland. There are numerous open questions about the current state of interaction between Adria and Eurasia under the Dinaric domain. One of the most interesting is the nature of lithospheric underthrusting of the Adriatic plate, e.g. length of the slab or varying slab disposition along the orogen. In this talk, I will describe two recent studies made to investigate the Dinaric upper mantle structure. In the first study we used S receiver functions to obtain the lithospheric thickness, while in the second one, we used the dispersion of Rayleigh waves to create a 3D shear wave velocity model. I will discuss the results of them in the context of regional tectonics.

David Whipp
2023-05-24 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
David Whipp
Can it be all so simple? Challenges and considerations applying thermochronology to understand crustal dynamics
Speaker is David Whipp
Professor, Department of Geosciences and Geography
Institute of Seismology
Helsinki Institute of Sustainability Science (HELSUS)
Supervisor for doctoral programme, Doctoral Programme in Geosciences
https://orcid.org/0000-0002-3820-6886

Iva Dasović
2023-05-31 00:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
The Berkovići (BIH) ML = 6.0 earthquake sequence from 22 April 2022
Iva Dasović
In the southern External Dinarides, and in the SE of Bosnia and Herzegovina, the Berkovići earthquake sequence started with the mainshock on 22 April 2022 21:07 UTC at focal depth 22 km with magnitude ML = 6.0 (Mw = 5.7). Preliminary estimation of the mainshock’s maximum intensity is VII EMS for Berkovići where 29% of buildings were damaged, and in Stolac a 28 y. o. woman lost her life to a rockfall caused by an earthquake. We analysed the first nine months, 22 April 2022 – 22 January 2023, of this sequence: seismicity and focal mechanisms, and we constructed a regional seismotectonic cross-section to delineate a potential seismogenic source of the mainshock.
Iva Dasović is an Associate Professor at the Andrija Mohorovičić Geophysical Institute, Department of Geophysics, at the University of Zagreb. She is visiting the department until 11th July, so if you would like to talk to her during that time please do not hesitate to get in touch, e.g., during the Geolunch, by email or in her temporary office 2F13c. This visit is organized as part of the CRONOS project that focuses on the Investigation of seismically vulnerable areas in Croatia and seismic ground motion assessment, and where Stéphane is involved as a partner here from GEO.

MSc “feedback”
2023-06-07 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
MSc “feedback”
Tor-Sebastian Rønneberg – “Fault crest stability during rifting” (Supervised by Haakon Fossen)
Synnøve Sørvåg Slåtsveen – “Improving interpretation of 3D Ground Penetrating Radar data in archaeology via attributes developed in seismic application to selected Norwegian sites.” (Supervised by Isabelle Lecomte)
Kristel Kaselaan – Detecting desalinisation in quick clays: geochemical analysis and interpretation of porewater data (Supervised by Elco Luijendijk)

Gerard Dam and William Helland Hansen
2023-06-09 14:00 - 15:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
1st presentation
Morphological modelling of rivers, tidal basins, and seas
Gerard Dam
UN-IHE (Delft) / COWI (Bergen) – gedm@cowi.com
In the last decades (process-based) morphological models have become popular tools in science and engineering to simulate sediment transport and bed level changes in rivers, tidal basins, and seas. With growing computational capacity, the capabilities of these models have become large. Now it is possible to model several hundred to even thousands of years of geomorphological changes with high resolution. Modeling long-term effects of human activities, climate change and sea level rise are themes that are investigated with these kinds of models. In this presentation I will show several examples of morphological modelling, how they work, how good they are on the long term and what is possible with these models.
2nd presentation (IAS practice session) 15 minutes
Coastal Changes in the 21st Cenutry: A sedimentology-perspective
William Helland Hansen

Gang Lu
2023-06-14 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Two-phase flow modelling for geological problems: Background, method, and applications
Gang Lu1,* Dave A. May2, and Ritske S. Huismans1
1Department of Earth Science, Bergen University, Bergen, N-5007, Norway
2Scripps Institution of Oceanography, UC San Diego
*Corresponding author: gang.lu@geo.uib.no
Two-phase flow, a system where Stokes flow and Darcy flow are coupled, is of great importance in Earth sciences. Examples of two-phase system include water migration in sedimentary basins/subduction zones/glaciers, and magma migration in subduction zones/mid-ocean ridges/hotspots. While the governing equations of the coupled two-phase system have been proposed long time ago, it remains challenging to solve the coupled system accurately in the zero-porosity limit, for example when melt is fully frozen below solidus temperature. In the limit when fluid phase is absent, the Darcy equation is redundant such that the coupled system becomes underdetermined. Here we propose a new three-field formulation of the two-phase system and present a robust finite-element implementation, which can successfully solve for the system where zero and non-zero porosity domains are both present. The new formulation is implemented using a 2-D finite-element discretization in FANTOM. We demonstrate the correctness of our implementation based on benchmarks against analytical solutions, which gives expected convergence rates in both space and time. We further present a number of example experiments, such as self-compaction, falling block, and mid-ocean ridge spreading, showing that this approach can robustly resolve zero- and non-zero-porosity domains simultaneously, and be used for a large range of applications in various geodynamic settings.

Prof Zoe Shipton & Prof Clare Bond
2023-06-15 14:00 - 15:00 | Auditorium 5, 3rd floor, Realfabyyget, 41 Allégaten, Bergen, 5007, Norway
Extra-ordinary Geo-lunch seminar

This week Prof. Zoe Shipton and Prof. Clare Bond are at GEO in connection with Vilde Dimmen’s PhD defense on Friday.

The hydraulic evolution of fracture networks under dynamic loading
Zoe Shipton, Department of Civil and Environmental Engineering, University of Strathclyde

Reflections on uncertainty in fault interpretation in seismic image data
Clare Bond School of Geosciences, University of Aberdeen

Frank Peel & Gillian Apps
2023-07-04 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Frank Peel & Gillian Apps (UT Austin) are visiting UiB this week and will give two talks.
1. Modern deposition on active salt, Iran – analog for North Sea Triassic? by Gillian Apps
2. Shallow or deep basin? What the paleo landscape seen on base Louann Salt reveals about salt deposition (Gulf of Mexico) by Frank Peel

Felix Halpaap
2023-08-23 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Unearthing a link between old and new plate boundaries and present-day seismotectonics of Svalbard: First insights from the new high-res 700k earthquake catalog of the European plate’s far North
Abstract:
Oceanic ridges and transform faults comprise nearly 45% of the Earth’s plate boundaries. Even though they have lower seismic moment release rates than convergent plate boundaries, these intricately segmented oceanic plate boundaries host a large part of Earth’s seismicity. Analyzing how their segmentation is expressed through their seismic behavior has not been commonly possible due to limited observations compared to plate boundaries on land. This knowledge gap has also hampered efforts to understand the causes of seismicity in regions adjacent to the plate boundaries, such as the Svalbard archipelago. A challenge for these remote areas is that there is often no overlap between event catalogs produced routinely from regional networks (typically with M>3.5) or from short local deployments (M<3). To close this gap, we apply a sensitive earthquake detection pipeline to complement a regional catalog over 25 years through HPC-supported template matching. We focus on the 3000 km of oceanic plate boundaries and adjacent areas in the European Arctic (68° – 87°N, 20°W – 40°E). From an initial dataset of 35k earthquakes, we obtain a new catalog of 700k events, including 150k events with high-resolution relative locations and ~80k glacial events. In this talk, I present this new data product with a focus on four areas where our analysis has unearthed completely new faults and seismicity patterns: (i) the amagmatically rifting Lena trough, (ii) the ultraslow-spreading Mohn and Knipovich ridges, (iii) the transform fault-bound Molloy deep, (iv) and the transtensional fault arrays of Nordaustlandet and Spitsbergen. We correlate the latter fault patterns with former plate-bounding thrust faults of the Timanian orogeny and compare the seismicity patterns with those found in transtensional settings along the San Andreas fault. Since this catalog contains far more new seismicity features than one can analyze alone, we invite everyone to explore this unique data product and to discuss new findings in the light of geodynamics and plate tectonics, field and structural geology, ridge tectonics and volcanism, and other phenomena such as methane seeps and glacial activity on Svalbard.

William Helland-Hansen
2023-08-30 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
100 Best Geosites of Norway

Melanie Kling & Lucas Valore
2023-09-13 12:15 - 13:00 | Kontinentalsokkelen (2G16e), Realfagbygget, Allégaten 41, Bergen, 5007, Norway
Where do they come from? Where do they go? Diamonds in Namibia
An indoor fieldtrip to Southern Namibia
by Lucas Valore and Melanie Kling
This May, Lucas and Melanie have had the opportunity to participate in a source-to-sink fieldtrip to Namibia as part of their training. There they saw and discussed where the source of the diamonds is, how and when they have been transported, and where they were finally deposited. During the fieldtrip they investigated locations in the Namibian desert and even the restricted government-controlled area, the Sperrgebiet, where the diamonds are currently mined.
This Wednesday they present some MARVELOUS photos from the fieldtrip and speak about the story of the diamonds. An important objective of source-to-sink studies is to disentangle overlapping forcing parameters and their individual impacts for stratigraphic and paleogeographic evolution. Therefore, they will also discuss a potential tectonic or climatic control behind the transport and deposition of the diamonds. Additionally, they promise
big outcrops due to minimal vegetation,
occasional antelopes and a story involving jackals,
spy-pictures from the diamond mines, and
insights on how the diamonds are mined.”
